Thesis Supervisor: Prof. Dr. A. Sezai SARAÇ

İSTANBUL TECHNICAL UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY

M.Sc. Thesis by

Nazif Uğur KAYA

Department : Polymer Science and Technology

Programme : Polymer Science and Technology

July 2010

SYNTHESIS AND CHARACTERIZATION OF COMPOSITES BY

POLYMERIZATION OF PYRROLE AND N-PHENYL PYRROLE ON

POLY(ACRYLONITRILE-CO-ACRYLIC ACID) MATRIX

İSTANBUL TECHNICAL UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY

M.Sc. Thesis by

Nazif Uğur Kaya

(515071015)

Date of submission : 30 July 2010

Date of defence examination: 2 August 2010

Supervisor (Chairman) : Prof. Dr. A.Sezai SARAÇ (ITU)

Members of the Examining Committee : Prof. Dr. Metin H. ACAR (ITU)

Prof. Dr. H. Yıldırım ERBİL (GIT)

July 2010

SYNTHESIS AND CHARACTERIZATION OF COMPOSITES BY

POLYMERIZATION OF PYRROLE AND N-PHENYL PYRROLE ON

POLY(ACRYLONITRILE-CO-ACRYLIC ACID) MATRIX

July 2010

İSTANBUL TEKNİK ÜNİVERSİTESİ FEN BİLİMLERİ ENSTİTÜSÜ

YÜKSEK LİSANS TEZİ

Nazif Uğur Kaya

(515071015)

Tezin Enstitüye Verildiği Tarih : 30 Temmuz 2010

Tezin Savunulduğu Tarih : 2 Ağustos 2010

Tez Danışmanı : Prof. Dr. A. Sezai SARAÇ (İTÜ)

Diğer Jüri Üyeleri : Prof. Dr. Metin H. ACAR (İTÜ)

Prof. Dr. H. Yıldırım ERBİL (GYTE)

PİROL VE N-FENİL PİROL’ ÜN POLİ(AKRİLONİTRİL-KO-AKRİLİK

ASİT) MATRİSİNDE POLİMERİZASYONU İLE KOMPOZİT

SENTEZİ VE KARAKTERİZASYONU

v

FOREWORD

I would like to express my deep appreciation and thanks for my advisor Prof. Dr. A.

Sezai SARAÇ. I am grateful to my family for their everlasting support.

I am also thankful to my collegues Suat ÇETĠNER, Bilge KILIÇ, Cansev TEZCAN,

Cem ÜNSAL, Damla ECEVĠT, Fatma Gül GÜLER, Ġlkkan ġENTÜRK, Melahat

ġAHĠN, Seher UZUNSAKAL, Timuçin BALKAN, Ulviye DALGIÇ for their helps

and composing our warm office atmosphere.

I would like to thank to my friends Tevfik Çağlar YÜCEL, Tuğba ANDER, Tuluhan

ERGĠN, Çağlar FIRAT, Kaan DEMĠRKAZIKSOY, S.Esra ÖZGÜL, Aslı

GENÇTÜRK, Koray YILMAZ, Can Metehan TURHAN, Ercan MUTLU, Saadettin

GÖKÇE, Erdal ÖNDER, Ġpek ÖSKEN, Argun Talat GÖKÇEÖREN, Erdem

YAVUZ, ġebnem ĠNCEOĞLU, Ari ġant BĠLAL, for their friendships and sincere

helps.

This work is supported by ITU Institute of Science and Technology.

July 2010

Thesis Nazif Uğur Kaya

Chemical Engineer

vi

vii

TABLE OF CONTENTS

Page

TABLE OF CONTENTS ......................................................................................... vii ABBREVIATIONS ................................................................................................... ix LIST OF TABLES .................................................................................................... xi

LIST OF FIGURES ................................................................................................ xiii SUMMARY .............................................................................................................. xv ÖZET ....................................................................................................................... xvii 1. INTRODUCTION .................................................................................................. 1

2. THEORETICAL PART ........................................................................................ 3 2.1 Electrical Conductivity ....................................................................................... 3

2.2 Conductive Polymers ......................................................................................... 4 2.2.1 Increase in conductivity with doping .......................................................... 7 2.3.1 Frequency and temperature variations with interfacial and dipolar

polarization ......................................................................................................... 14

3. EXPERIMENTAL PART ................................................................................... 17 3.1 Materials ........................................................................................................... 17 3.2 Synthesis of P(AN-co-AA) .............................................................................. 17

3.3 Preparation of P(AN-co-AA)/PPy Composite Films ....................................... 19 3.4 Preparation of Nanofibers of P(AN-co-AA)/PPy Composites ......................... 21 3.5 Synthesis of PPy ............................................................................................... 22

3.6 Characterization of P(AN-co-AA), Composite Films and Nanofibers ............ 22 3.7 Results and Discussion ..................................................................................... 25

3.7.1 FTIR-ATR spectrophotometric analysis ....................................................... 25 3.7.1.1 FT-IR calibration curve for P(AN-co-AA) pellet .............................. 25 3.7.1.2 P(AN-co-AA) ..................................................................................... 26

3.7.1.3 P(AN-co-AA)-PPy and P(AN-co-AA)-PNPhPy composite films ..... 28 3.7.1.4 P(AN-co-AA), P(AN-co-AA)-PPy and P(AN-co-AA)-PNPhPy

composite nanofibers ..................................................................................... 30 3.7.2 UV-Visible spectrophotometric analysis .................................................. 31 3.7.3 Nuclear magnetic resonance measurements (NMR) ................................. 32

3.7.3.1 NMR of P(AN-co-AA) ...................................................................... 32 3.7.3.2 NMR of PPy ....................................................................................... 34

3.7.4 Molecular weight determination ............................................................... 34 3.7.5 Dielectric and conductivity measurements ............................................... 35

3.7.6 Thermogravimetric analysis measurements (TGA) .................................. 43 3.7.7 Differential scanning calorimetry measurement (DSC) ............................ 45 3.7.8 Scanning electron microscope measurements (SEM) ............................... 45

4. CONCLUSION AND RECOMMENDATIONS ............................................... 51 REFERENCES ......................................................................................................... 53 CURRICULUM VITA ............................................................................................ 57

viii

ix

ABBREVIATIONS

AA : Acrylic Acid

AN : Acrylonitrile

CAN : Ceric Ammonium Nitrate

DMF : Dimethylformamide

DSC : Differential Scanning Calorimetry

FT-IR : Fourrier Transform Infrared

NMR : Nuclear Magnetic Resonance

NPhPy : N-Phenyl Pyrrole

PAA : Polyacrylic acid

PAN : Polyacrylonitrile

PNPhPy : Poly(N-Phenyl Pyrrole)

PPy : Polypyrrole

Py : Pyrrole

SEM : Scanning Electron Microscope

TGA : Thermogravimetric Analysis

x

xi

LIST OF TABLES

Page

Table 3.1: C(mole%) of PAN in PAN/PAA blends and log(T0/T) values at 2243cm-1

.

............................................................................................................................ 26

xii

xiii

LIST OF FIGURES

Page

Figure 2.1 : Band gap differences metals, semiconductors and insulators [20]…….. 5 Figure 2.2 : Repeat units of several electronic polymers [23]………………………. 6 Figure 2.3 : Electromagnetic spectrum. The wavelength λ depends on the medium

in which the electromagnetic wave propagates [24]……………………………. 8

Figure 2.4 : Elelctric flux between the metal plates in vacuum space [24]…………. 9 Figure 2.5 : Dielectric material is placed between the metal plates [24]…………... 11 Figure 2.6 : Principles of polarizations and frequency trend of polarization effects

[18]…………………………………………………………………………….. 13 Figure 3.1 : Monomers used in synthesis of P(AN-co-AA). .................................... 17

Figure 3.2 : Copolymerization mechanism of AN and AA. ..................................... 18 Figure 3.3 : Experimental setup for synthesis of P(AN-co-AA)............................... 18

Figure 3.4 : Procedure for P(AN-co-AA)/PPy and P(AN-co-AA)/PNPhPy composite

film formation. ................................................................................................... 19 Figure 3.5 : Pyrrole (Py) and N-Phenyl pyrrole (NPhPy). ........................................ 20

Figure 3.6 : Polymerization mechanism of PPy [30]. ............................................... 20 Figure 3.7 : Experimental setup of electrospinning [31]. ......................................... 21

Figure 3.8 : Perkin Elmer, Spectrum One FTIR-ATR Spectrophotometer. ............. 22 Figure 3.9 : Perkin Elmer, Lambda 45 UV-Visible Spectrophotometer. .................. 23

Figure 3.10 : 250 MHz Brucker AC Aspect 3000 NMR spectrometer [32]. ............ 23 Figure 3.11 : Novocontrol broadband dielectric spectrometer. ................................ 24

Figure 3.12 : Placing film samples between electrodes on Novocontrol broadband

dielectric spectrometer. ...................................................................................... 24 Figure 3.13 : Mini-SEM, SEC, SEN-3000M. ........................................................... 25

Figure 3.14 : Figure FT-IR of KBr pellets of synthesized P(AN-co-AA) and blends

including varying ratio of PAA and PAN in transmission mode. ...................... 25

Figure 3.15 : Calibration curve for blends of PAN and PAA including varying CPAN.

............................................................................................................................ 26 Figure 3.16 : FTIR-ATR Characterization PAN (Aldrich) and P(AN-co-AA). ....... 27

Figure 3.17 : FTIR-ATR Characterization P(AN-co-AA) with different AN/AA

ratios. .................................................................................................................. 27 Figure 3.18 : Tentative mechanism for intermolecular interaction between P(AN-co-

AA), PPy chains and DMF. ............................................................................... 29

Figure 3.19 : FTIR-ATR Characterization of P(AN-co-AA) films and PPy including

P(AN-co-AA) films. ........................................................................................... 29 Figure 3.20 : FTIR-ATR Characterization of P(AN-co-AA) films and PNPhPy

including P(AN-co-AA) films. .......................................................................... 30 Figure 3.21 : FTIR-ATR characterization of P(AN-co-AA), P(AN-co-AA)/PPy and

P(AN-co-AA)/PNPhPy nanofibers. ................................................................... 31 Figure 3.22 : UV-Visible absorbance vs. wavelength of solution of PPy in methanol.

............................................................................................................................ 32

xiv

Figure 3.23 : 1

H NMR spectroscopy of P(AN-co-AA) in DMSO-d6 solvent (0.0-

10ppm). .............................................................................................................. 33 Figure 3.24 :

1H NMR spectroscopy of P(AN-co-AA) in DMSO-d6 solvent (0.0-5.0

ppm). .................................................................................................................. 33

Figure 3.25 : 1

H NMR spectroscopy of P(AN-co-AA) in DMSO-d6 solvent (6.0-10.0

ppm). .................................................................................................................. 34 Figure 3.26 :

1H NMR spectroscopy of PPy in DMSO-d6 solvent. .......................... 34

Figure 3.27 : ηsp/C vs. C of the P(AN-co-AA) in DMF. ........................................... 35 Figure 3.28 : a. Conductivity (S/cm) values of P(AN-co-AA) and P(AN-co-

AA)/PNPhPy films (For 0.72 and 1.44 mmoles of initially added NPhPy) b.

Conductivity (S/cm) values of P(AN-co-AA), P(AN-co-AA)/PPy and P(AN-co-

AA)/PNPhPy films (For 1.44 mmoles of initially added Py and NPhPy). ........ 36 Figure 3.29 : a. Real permittivity (Eps’) and b. imaginary permittivity (Eps”) of

P(AN-co-AA) and P(AN-co-AA)/PNPhPy films (For 0.72 and 1.44 mmoles of

initially added NPhPy). ...................................................................................... 37 Figure 3.30 : a. Real permittivity (Eps’) and b. Imaginary permittivity (Eps”) of

P(AN-co-AA), P(AN-co-AA)/PPy and P(AN-co-AA)/PNPhPy films (For 1.44

mmoles of initially added Py and PhPy). ........................................................... 38 Figure 3.31 : a. Modulus’ (M’) and b. Modulus” (M”) of P(AN-co-AA) and P(AN-

co-AA)/PNPhPy films (For 0.72 and 1.44 mmoles of initially added NPhPy). 40

Figure 3.32 : a. Modulus’ (M’) and b. Modulus” (M”) of P(AN-co-AA), P(AN-co-

AA)/PPy and P(AN-co-AA)/PNPhPy films (For 1.44 mmoles of initially added

Py and PhPy). ..................................................................................................... 41

Figure 3.33 : Modulus’ (M’) vs. Modulus” (M”) of P(AN-co-AA), P(AN-co-

AA)/PPy and P(AN-co-AA)/PNPhPy films (For 1.44 mmoles of initially added

Py and PhPy). ..................................................................................................... 42

Figure 3.34 : Temperature vs. Derivative Weight (%Weight/min) from TGA of

P(AN-co-AA), PPy and P(AN-co-AA)/PPy composite film including 1.44

mmoles initially fed Py. ..................................................................................... 43

Figure 3.35 : Temperature vs. % Weight from TGA of P(AN-co-AA), PPy and

P(AN-co-AA)/PPy composite film including 1.44 mmoles initially fed Py. ..... 44 Figure 3.36 : DSC of P(AN-co-AA) including 2.67 AA by % mole. ....................... 45

Figure 3.37 : SEM images of nanofibers of pure P(AN-co-AA). ............................. 46 Figure 3.38 : SEM images of nanofibers of P(AN-co-AA)/PPy composite with

magnification of x1500. ..................................................................................... 47 Figure 3.39 : SEM images of nanofibers of P(AN-co-AA)/PPy composite with

magnification of x3000. ..................................................................................... 47

Figure 3.40 : Nanofiber diameter distribution of P(AN-co-AA)/PPy composite. .... 48 Figure 3.41 : SEM images of nanofibers of P(AN-co-AA)/PNPhPy composite with

magnification of x1000. ..................................................................................... 48 Figure 3.42 : SEM images of nanofibers of P(AN-co-AA)/PNPhPy composite with

magnification of x5000. ..................................................................................... 49 Figure 3.43 : Nanofiber diameter distribution of P(AN-co-AA)/PNPhPy composite.

............................................................................................................................ 49

xv

SYNTHESIS AND CHARACTERIZATION OF COMPOSITES BY

POLYMERIZATION OF PYRROLE AND N-PHENYL PYRROLE ON

POLY(ACRYLONITRILE-CO-ACRYLIC ACID) MATRIX

SUMMARY

In this study, influence of conjugated polymer on AC electrical conductivity and

dielectric properties of copolymer of acrylonitrile (AN) and acrylic acid (AA)

(P(AN-co-AA)) composite films were investigated. In-situ polymerized polypyrrole

(PPy) and poly(N-phenylpyrrole) (PNPhPy) on P(AN-co-AA) matrix were used as

conductive polymer. First, P(AN-co-AA) was synthesized by oxidative

copolymerization of AN and AA monomers in aqueous medium. Afterwards, pyrrole

(Py) and N-phenyl pyrrole (NPhPy) were polymerized on P(AN-co-AA) matrix in

dimethylformamide (DMF). Ce(IV) salt was used as an oxidant for both copolymer

formation and polymerization of Py and NPhPy on P(AN-co-AA) matrix. Composite

films were then acquired by evaporation of DMF. Spectroscopic, electrical and

thermal properties of composite films were analyzed. In fourier transform infrared

spectroscopoy (FTIR-ATR) measurements, as the ratio of initially added acrylic acid

to acrylonitrile increased, the ratio of absorbance values of characteristic peaks of

PAA segments to PAN segments also increased. Concurrently, the ratio of

absorbance values of peaks respectively relating to PPy and PAN rose as initially

feed amount of PPy increased. Molecular weight of P(AN-co-AA) was calculated

from intrinsic viscosity, [η], which was measured with Ubbelohde viscometer and

AA composition in copolymer was calculated with 1H NMR. In all samples, real

permittivity (Eps’) and imaginary permittivity (Eps”) decreased as the frequency (f)

increased; they remained stable in the region of 10 Hz to 107. -H atoms related to

PPy did not enhance conductivity and dielectric permittivity values of composite

films as compared to PNPhPy including of those due to less polarization of –H atoms

than phenyl groups. TGA thermograms of pure P(AN-co-AA), P(AN-co-AA)/PPy

including initially fed 1.44 mmoles of Py composite film and PPy which was

synthesized in DMF medium without P(AN-co-AA) matrix indicated intrinsic weight

losses showing intermolecular interaction between PPy, DMF and P(AN-co-AA).

Also, nanofibers of P(AN-co-AA) and in-situ polymerized PPy, PNPhPy on P(AN-

co-AA) matrix were acquired by electrospinning method; nanofiber diameters of

composites were calculated. Spectroscopic and morphological properties of

nanofibers were investigated.

xvi

.

xvii

PİROL VE N-FENİL PİROL’ ÜN POLİ(AKRİLONİTRİL-KO-AKRİLİK

ASİT) MATRİSİNDE POLİMERİZASYONU İLE KOMPOZİT SENTEZİ VE

KARAKTERİZASYONU

ÖZET

Bu çalıĢmada, konjuge polimerlerin akrilonitril-akrilik asit kopolimeri (P(AN-ko-

AA)) kompozitlere ait AC elektriksel iletkenlik ve dielektrik özellikleri üzerine

etkileri incelenmiĢtir. Akrilonitril (AN) ve akrilik asidin (AA) kopolimeri (P(AN-ko-

AA)) matrisi üzerinde pirol (Py) ve N-Fenilpirol (NFPy) polimerleĢtirilmiĢtir.

Polipirol (PPy) Poli(N-Fenilpirol) (PNFPy) iletken polimer olarak kullanılmıĢtır. Ġlk

olarak, akrilonitril (AN) ve akrilik asit (AA) monomerlerinin sulu ortamda oksidatif

kopolimerizasyonları gerçekleĢtirilmiĢtir. Py ve NFPy’ nin dimetilformamid (DMF)

içerisinde çözülmüĢ P(AN-ko-AA) matrisinde polimerizasyonları

gerçekleĢtirilmiĢtir. Ce(IV) tuzu, hem kopolimer sentezinde, hem de Py ve NFPy’

nin polimerleĢtirilmesinde oksidant olarak kullanılmıĢtır. OluĢturulan kompozitlerin

filmleri çözücünün (DMF) uzaklaĢtırılmasıyla elde edilmiĢ ve bu filmlerin

spektroskopik, elektriksel ve ısıl özellikleri incelenmiĢtir. Yapılan FTIR-ATR ölçüm

sonuçlarında, değiĢik AA ve AN oranlarında çalıĢıldığında, AA/AN oranı arttıkça

poliakrilik asite (PAA) ait CO gerilme pikinin absorbansının poliakrilonitrile (PAN)

ait C≡N gerilme pikinin absorbansına oranının da arttığı gözlemlenmiĢtir. Ayrıca,

PPy’ ye ait CN gerilme pikinin absorbansının PAN’ a ait C≡N gerilme pikinin

absorbansına oranının Py monomer miktarının artıĢıyla uyum gösterdiği tespit

edilmiĢtir. Ubbelohde viskozimetresi ile P(AN-ko-AA) nın Mv değeri bulunmuĢ, 1H

NMR yöntemiyle kopolimerdeki AA yüzdesi hesaplanmıĢtır. Bütün film

örneklerinde, dielektrik sabiti (Eps’) ve dielektrik kaybı (Eps”) artan frekans (f) ile

birlikte azalma göstermiĢ; 10 Hz ile 107 Hz aralığında sabit bir değer göstermiĢtir.

PPy’ ye ait –H atomlarının iletkenlik ve dielektrik geçirgenlik değerlerine katkıları,

PNFPy’ ye ait fenil gruplarınınkinden daha az olmuĢtur. Bunun sebebi yan grup olan

fenil gruplarının, -H atomlarına oranla iletken polimer zincirine daha polar bir yapı

kazandırmasıdır. Termogravimetrik Analiz (TGA) ölçümlerinde, saf P(AN-ko-AA),

PPy içeren P(AN-ko-AA) kompozit film ve P(AN-ko-AA) matrisi olmadan DMF

içerisinde polimerleĢtirilen PPy’ nin kütle kayıpları gözlemlenmiĢtir. Bu Ģekilde PPy,

DMF ve P(AN-ko-AA) arasındaki moleküllerarası etkileĢim gözlemlenmiĢtir.

Ayrıca, PPy ve PNFPy içeren ve içermeyen P(AN-ko-AA) kompozitlerin

nanofiberleri elektrospining metoduyla elde edilmiĢtir. Nanofiberlerin çapları

hesaplanmıĢtır, spektroskopik ve morfolojik karakterizasyonları gerçekleĢtirilmiĢtir.

xviii

.

1

1. INTRODUCTION

Polyacrylonitrile (PAN) has been used in many applications as a constituent of a

membrane, fiber manufacturing [1]. Polyacrylic acid (PAA) is commonly used in

toothpaste, cosmetics, hydraulic fluids, and even liquid rocket fuels . Floor coverings

and waterproof gloves are the polymeric materials that can be thickened during

fabrication. Acrylic acid and its copolymers are purposed as an assistant to provide

dispersion of pigments in paints [2]. Cross-linked PAA has also common uses as ion

exchange resins and hydrogels [3]. Copolymer of acrylonitrile (AN) and acrylic acid

(AA) has an application in water-swollen artificial kidney membranes due to its

transport properties [4]. Molecularly imprinted membranes is another region for

P(AN-co-AA). Copolymer has the properties of both a good membrane due to PAN

section and recognition capacity supplied by PAA [5]. P(AN-co-AA) is also

constructed as glucose biosensor [6]. Various polymerization methods are chosen for

synthesizing P(AN-co-AA) such as chemical [6,7,8,9], electrochemical [7-10] and

photopolymerization [11]. Dimethylformamide (DMF), dimethylsulfoxide (DMSO),

water can be used as medium in chemical method [7,8,9]. Despite conductive

polymers benefit excellent electrical properties due to extended π-electron

conjugation, depending on their weak stability and having difficulties while

processing, are applied in limited regions [12-13]. Polypyrrole (PPy) is one of the

most common conjugated polymer for commercial uses due to its good

environmental stability, simple synthesis and higher electrical conductivity as

compared to other conducting polymers [14]. Polymer composites of PAN/PPy,

P(AN-co-AA)/PPy and P(AN-co-SS)/PPy were synthesized by impregnating pyrrole

monomer into the matrix followed by the polymerization of pyrrole in the matrix

film. Anionic moieties supplied better electrostatic interaction between the polymer

matrix and conducting polymer resulting better electrical properties as polymeric

matrix roled as polymeric dopant [12]. In the case pyrrole is oxidatively polymerized

on P(MMA-co-AA) matrix, carboxylate groups provided stable dispersions [4].

Electromagnetic interference (EMI) shielding has crucial importance on electronic

2

and communication industries [15]. Conducting polymers are suitable materials for

eliminating EMI due to their high values of conductivity and dielectric permittivity

as compared with other polymers. Not only they are lightweight, but also more

flexible than metals and do not corrode [16]. In order to absorb radar, materials

should include resistive or magnetic materials transforming electromagnetic energy

into heat. PPy has satisfactory electrical properties to be selected for a radar

absorbing material [17].

In this study, influence of conjugated polymer on AC electrical conductivity and

dielectric properties of P(AN-co-AA) composite films were investigated, while

polypyrrole (PPy) and poly(N-phenylpyrrole) (PNPhPy) were used as conductive

polymers. P(AN-co-AA), which was used as matrix in composite film formation,

was synthesized by oxidative copolymerization of AN and AA monomers in aqueous

medium. Afterwards, pyrrole (Py) and N-phenylpyrrole (NPhPy) were polymerized

on P(AN-co-AA) matrix in dimethylformamide (DMF). Ce(IV) salt was used as an

oxidant for both copolymer formation and in-situ matrix polymerization due its

strong oxidizing power. Composite films were then acquired by partially evaporation

of DMF. Py was polymerized in DMF without copolymer matrix by using Ce(IV)

salt as the oxidant. Spectroscopic, electrical and thermal properties of thin films and

PPy were analyzed. Also, nanofibers of P(AN-co-AA) and in-situ polymerized

pyrrole (Py) and N-phenyl pyrrole (NPhPy) on P(AN-co-AA) matrix were acquired

by electrospinning method. Spectroscopic and morphological properties of

nanofibers were investigated.

3

2. THEORETICAL PART

2.1 Electrical Conductivity

The electron conductivity of solids is determined by their atomic, crystal, or

amorphous structure. Metals are good electron conductors. Their atoms all have in

their outer shell one to three electrons that are free to move throughout the metals

and alloys in “conduction bands”, since the electrons in this state are not associated

with any particular atom, pair or group of atoms.

If the atoms of these same elements are combined into molecules with different types

of atoms which are lacking one to three electrons in their outer shell, such as oxygen,

sulfur or the halogens (fluorine, chlorine, bromine, and iodine), the electrons from

the outer shell of the metallic elements tend to transfer completely to the outer shell

of the combining elements, filling that shell and thereby forming compound

molecules that are ion pairs (for example: Na+C1

– and Mg

+2O

+2). These compounds

form solid ionic crystals where the electrons are tightly bound in negative ions

balanced by an equal total charge of positive ions. These are not usually electron

conductors, except at very high electric fields or under ionizing radiation conditions

In other cases, binding between atoms in molecules occurs by sharing electrons

between atoms forming some common electron orbits. This type of bonding is

predominant in organic carbon compounds. Electrons in organic materials are usually

attached to particular molecules forming negative ions with an equal charge of

positive ions so they do not contribute to electron conduction. Electrons restricted to

individual atoms or interatomic bonds are in the “band theory” representation of

conduction said to be in the “valence band”. Sufficient thermal energy or ionizing

radiation can lift some into the conduction band, but the required energy is high in

the case of most insulating materials. Therefore, electron conduction is not common

(except at very high electric fields) in conventional insulating materia1s.

The energy gap between the valence band and the conduction band in metals is

negligible, and the valence and conduction bands are said to overlap. In intrinsic

4

semiconductors, such as pure silicon and pure germanium, the conduction-valence

band gaps are 1.1 to 1.2 and 0.72 to 0.78 eV (electron volts), respectively; and these

pure crystals are not very good electron conductors compared to metals.

Also, electron semiconduction has been noted with inorganic molecules with

extended chains of alternating double and single carbon-carbon bonds. As in

benzene, naphthalene, and anthracene, the pi orbit electrons associated with

alternating single and double bonds are not associated with any particular atom and

are able to move around the ring or along molecular chains having “conjugated”

double bonds. The energy barrier between such internally semiconducting molecules

is high, however, so electrons do not easily move from molecule to molecule, unless

some doping agent is added to reduce this barrier [18].

2.2 Conductive Polymers

In 1970s, a new class of polymers possessing high electronic conductivity

(electronically conducting polymers) in the partially oxidized (or, less frequently, in

the reduced) state was discovered. Three collaborating scientists, Alan J. Heeger,

Alan G. MacDiarmid and Hideki Shirakawa, played a major role in this

breakthrough, and they received the Nobel Prize in Chemistry in 2000 “for the

discovery and development of electronically conductive polymers”.

There were several precursors to this discovery, including theoretical predictions

made by physicists and quantum chemists, and different conducting polymers that

had already been prepared. For instance, as early as 1862, Henry Letheby prepared

polyaniline by the anodic oxidation of aniline, which was conductive and showed

electrochromic behavior. Nevertheless, the preparation of polyacetylene by

Shirakawa and coworkers and the discovery of the large increase in its conductivity

after “doping” by the group led by MacDiarmid and Heeger actually launched this

new field of research [19].

5

Conducting polymers are organic materials that generally possess an extended

conjugated π-electron system along a polymer backbone. For this reason, the terms

conducting polymer and conjugated polymer are often used synonymously. Like

dyes, conjugated polymers differ from saturated systems by having a smaller highest-

occupied molecular orbital to lowest-unoccupied molecular orbital (HOMO–

LUMO)-energy gap which gives the visual impression that they are colored but does

not necessarily provide any electrical conductivity. Conduction of electric charges

requires unoccupied energy states for extra electrons or electron deficiencies (holes)

to be available and the relatively unhindered movement of charge throughout the

conducting material.

Figure 2.1 : Band gap differences metals, semiconductors and insulators [20].

Conducting polymers have high electron affinities or low oxidation potentials (in

most cases either one or the other). They can be either readily reduced (doped with

electron donors) or readily oxidized (doped with electron acceptors). Addition of

charge creates new and unfilled electronic energy states that lie within the original

HOMO–LUMO energy gap. It is the formation of these gap levels and the quasi-one-

dimensional rather than crystal lattice structure which distinguishes the

semiconductor physics of conjugated polymers from that of conventional inorganic

semiconductors. Both classes of materials have in common that the presence of

added charge by the doping process causes a significant rise in electrical

conductivity, confirming that charge can be transported through the material [21].

6

The common electronic feature of pristine (undoped) conducting polymers is the π-

conjugated system which is formed by overlap of carbon pz orbitals and alternating

carbon-carbon bond length. (In some systems, notably polyaniline, nitrogen pz

orbitals and C6 rings also are part of the conjugation path.) Figure 2.2 shows the

chemical repeat units of the pristine forms of several families of conducting and

semiconducting polymers, i.e., trans-polyacetylene [t-(CH)x], the leucoemeraldine

base (LEB), emeraldine base (EB) and pernigraniline base (PNB) form of polyaniline

(PAN, polypyrrole (PPy) polythiophene (PT), poly(p-phenylene) (PPP), and poly(p-

phenylene vinylene) (PPV) [22].

Figure 2.2 : Repeat units of several electronic polymers [23].

7

2.2.1 Increase in conductivity with doping

The conductivities of the pristine electronic polymers aretransformed from insulating

to conducting through doping. Both n-type (electron donating, e.g., Na, K, Li, Ca,

tetrabutylammonium) and p-type (electron accepting, e.g., PF6, BF4, Cl, AsF6)

dopants have been used. The doping typically is done using vapors or solutions of the

dopant, or electrochemically. (In some circumstances, the polymer and dopant are

dissolved in the same solvent before forming the film or powder.) The polymer

backbone and dopant ions form a rich variety of new three-dimensional structures

[22].

2.3 Electrical Properties of Polymers

The basic distinction between a semiconductor and a dielectric (or insulator) lies in

the difference in the energy band gap. At the normal ranges of temperatures and

pressures, the dominant charge carriers in a semiconductor are generated mainly by

thermal excitation in the bulk because the semiconductor has a small energy band

gap; hence, a small amount of energy is sufficient to excite electrons from full

valence band to an upper empty conduction band. In a dielectric, charge carriers are

mainly injected from the electrical contacts or other external sources simply because

a dielectric’s energy band gap is relatively large, so a higher amount of energy is

required for such band-to-band transitions. A material consists mainly of atoms or

molecules, which comprise electrons and nuclei. The electrons in the outermost shell

of atoms, bound to the atoms or molecules coupled with the free charges interact

with external forces, such as electric fields, magnetic fields, electromagnetic waves,

mechanical stress, or temperature, resulting in the occurrence of all dielectric

phenomena. For nonmagnetic dielectric materials, the dielectric phenomena include

mainly electric polarization; resonance; relaxation; energy storage; energy

dissipation; thermal, mechanical, and optical effects and their interrelations; and

electrical aging and destructive breakdown it [24].

8

Figure 2.3 : Electromagnetic spectrum. The wavelength λ depends on the

medium in which the electromagnetic wave propagates [24].

Since electrical insulation is used primarily for its nonconducting characteristic, the

relatively low level of conductivity it does have can be an important limitation to its

effective use. Therefore, it is very important to know what this level is and the

factors that influence it. The conductivity or the AC loss tangent, tan δ, or loss factor,

ε′ tan δ, (ε′ is the relative dielectric constant) are commonly used as quality control

parameters for electrical insulation.

The metals and semiconductors are primarily electron conductors with structures

which permit extensive movement of electrons in conduction bands. “Hole” or P

(positive) type semiconductors also physically conduct by electrons moving from

hole to hole. Since a “hole” is a positive site where an electron is missing, it seems as

if positive charges were moving in the opposite direction. In contrast, except at very

high electric fields or under ionizing radiation conditions, there are very few

electrons in common insulating materials, which are not strongly attached to an atom

or molecule forming ions. Consequently conductivity of dielectrics is usually due to

the translation of positive and negative charged ions of atomic or molecular size [18].

9

Electric polarization refers to a phenomenon of the relative displacement of the

negative and positive charges of atoms or molecules, the orientation of existing

dipoles toward the direction of the field, or the separation of mobile charge carriers at

the interfaces of impurities or other defect boundaries, caused by an external

electric field. Electric polarization can also be thought of as charge redistribution in a

material caused by an external electric field. The work done for the charge

redistribution and the energy loss involved in the redistribution process require an

energy supply. The whole polarization process is performed at the expense of the

potential energy released from this process, because the total potential energy of the

system in an electric field is smaller after electric polarization than before it [24].

When an atom or molecule is placed in an electric field, the electrons in the atom are

displaced very slightly toward the positive direction of the field. This occurs almost

instantly within times less than a half cycle of optical frequency [18].

A simple system in vacuum space (free space) was demonstrated in Figure 2.4

consisting of two metal plates parallel to each other with an are A, each and a

separation d, which is much smaller than the linear dimension of the plates, so that

the fringing effect at the edges can be ignored by approximation.

Figure 2.4 : Elelctric flux between the metal plates in vacuum space [24].

When a positive charge +Q was introduced on the upper plate and a negative charge -

Q of the same magnitude on the lower plate by connecting a steady DC voltage

supply across the plates, the system was charged as a capacitor. Then disconnecting

the supply from the system as soon as the charge has been accumulated to the desired

10

value Q, will create a potential difference between the plates V that is proportional to

Q.

(2.1)

(2.2)

C is called the capacitance. By denoting the surface charge density on the plates as

δs, the charge Q can be expressed as:

(2.3)

E was the electric field strength between the plates and A is the area of the plates.

(2.4)

Thus,

(2.5)

(2.6)

Where ε is the real permittivity, also dielectric constant, of the material filled

between the two plates. Therefore, permittivity of vacuum space was:

(2.7)

When a material is placed inside the space between the metal plates with the original

surface of density δs (blue part in the Figure 2.5), unaltered, this causes the potential

between the plates produced by the original charge Q on the plates to decrease to a

smaller value.

11

Figure 2.5 : Dielectric material is placed between the metal plates [24].

However, the induced charges on the surfaces of the material, δi, decrease the

original electric field by causing an opposing electric field to the original field. Thus,

dielectric permittivity, , is calculated as:

(2.8)

(2.9)

The dielectric material between the plates is not in phase with the applied voltage,

but by an angle, Δ (0° < Δ < 90°), which is called as the loss angle.

ε″ is called as imaginary permittivity, also dielectric loss, of the material, and tan Δ

as the dissipation factor. So tan Δ is shown as [25]:

(2.10)

Complex modulus is obtained by converting permittivity values; real (M’) and

imaginary (M”) parts of the complex electric modulus can be written as [25]:

(2.11)

(2.12)

12

For most materials, the dielectric constant is independent of the electric field strength

for fields below a certain critical field, at or above which carrier injection into the

material becomes important. The dielectric constant depends strongly on the

frequency of the alternating electric field or the rate of the change of the time-

varying field. It also depends on the chemical structure and the imperfections

(defects) of the material, as well as on other physical parameters including

temperature and pressure, etc. A dielectric material is made up of atoms or molecules

that possess one or more of five basic types of electric polarization as it is seen in

Figure 2.6:

1. Electronic polarization

2. Atomic or ionic polarization

3. Dipolar polarization

4. Spontaneous polarization

5. Interface or space charge polarization.

Each type of polarization requires time to perform; this is why the degree of the

overall polarization depends on the time variation of the electric field (frequency of

the applied AC) [24].

Ionic-interfacial and dipolar polarization are the most important for most organic

liquid and resin electrical insulation, since they are associated with conduction and

dielectric loss at commonly used frequencies. A form of polarization and associated

conduction like ionic-interfacial are also observed in inorganic glasses and ceramics

at lower frequencies and increases with increased temperature [18].

13

Figure 2.6 : Principles of polarizations and frequency trend of polarization

effects [18].

Electron polarization is responsible for the optical refractive index, η, and is part of

the dielectric constant of all dielectric materials. The magnitude of the refractive

index and its contribution to the dielectric constant, ε’∞ = η2, is essentially constant

from zero frequency up to the optical frequency range where dispersion (a slight

increase) and resonance absorption, attenuation, occurs at specific frequencies. This

type of polarization does not contribute to conduction or dielectric loss in

conventional electrical insulating materia1s at frequencies common1y used in

insulation app1ications. The values of η for dielectric liquids range from about 1.2

for fluorocarbon liquids up to about 1.6 for chlorinated hydrocarbon liquids. η

increases with the electron density and with aromatic (benzene like) molecular

structures, which have a greater electron polarizability. For example, η for benzene is

1.498 compared with 1.372 for hexane [18].

14

2.3.1 Frequency and temperature variations with interfacial and dipolar

polarization

Interfacial and dipolar polarizations depend on the effective internal viscosity

presented by the material to the movement of ions or rotation of dipole molecules,

respectively. The longer range movement of ions up to barriers typically takes a

longer time to develop polarization than the simple rotation of dipoles. Therefore,

ionic interfacial polarization is observed at lower frequencies, where the half cycle is

of sufficient time [18].

2.4 Electrospinning Method

Electrospinning technique was originally developed by Zeleny (1914) to prepare

interconnected webs of fibers from polymer solutions or melts. It is a process that

applies a high voltage to create electrically charged jets of a polymer solution. The

jets within the electric field are directed toward the grounded target, during which

they dry to form fibers [26]. This technique has been recognized as an effective way

to fabricate polymeric nanofibers with diameter ranging from several micrometers

down to tens of nanometers. Among various polymers, acrylonitrile-based homo-

and co-polymers were most recently fabricated into nanofibrous materials with

reinforcing, superhydrophobic and catalytic properties [27]. Electrospinning uses

electrostatic forces to produce fine fibers from polymer solutions or melts and the

fibers thus produced have a thinner diameter and a larger surface area than those

obtained from conventional spinning processes. Furthermore, a DC voltage in the

range of several tens of kVs is necessary to generate the electrospinning [28].

The minimum equipment requirements for demonstration of simple electrospinning

in the laboratory are as follows:

1. A viscous polymer solution or a melt.

2. An electrode (hollow tubular or solid) that is maintained in contact with

the polymer solution.

3. A high-voltage DC generator connected to the electrode.

4. A grounded or oppositely charged surface to collect the nanofibers.

Figure 3.4 is the schematic description of experimental setup for electrospinning.

15

The electrospinning process is solely governed by many parameters, classified

broadly into solution parameters, process parameters, and ambient parameters.

Solution parameters include viscosity, conductivity, molecular weight, and surface

tension and process parameters include applied electric field, tip to collector distance

and feeding or flow rate [28,29].

16

17

3. EXPERIMENTAL PART

3.1 Materials

AN (Acrylonitrile, C3H3N, AKSA), AA (Acrylic Acid, C3H4O2, SGS), Py (Pyrrole,

C4H5N, Aldrich), NPhPy (N-Phenyl pyrrole, C10H9N, Aldrich), DMF

(Dimethylformamide, C3H7NO, Riedel-de Haen), CAN (Ceric Ammonium Nitrate,

(NH4)2Ce(NO3)6, BDH), HNO3 (Fluka, 65%). PAN (Polyacrylonitrile, (C3H4N)150,000,

Aldrich), PAA (Polyacrylic acid, (C3H4O2)100,000, Fluka)

3.2 Synthesis of P(AN-co-AA)

A mixed solution of acrylic acid (AA) and water was put into a three-necked round

bottomed flask with a condenser, after acrylonitrile (AN) was placed. Monomers

were shown in Figure 3.1.

Figure 3.1 : Monomers used in synthesis of P(AN-co-AA).

P(AN-co-AA) was synthesized in four different initial feed AA/AN ratios by weight

(5/95, 10/90, 20/80, 40/60) Constant total weight of monomers of 5g was applied at

each polymerizations. Thus, for the reaction including AA/AN ratio of 5/95, AA

amount was 0.25g and AN amount was 4.75g. The mixture was stirred with a

magnetic stirrer for 15 minutes at 60°C. Then solution of 5 mM ceric ammonium

nitrate (CAN) in 0.1M HNO3 was added dropwise with a syringe in 5 minutes. Free-

radical copolymerization mechanism was shown in Figure 3.2.

18

Figure 3.2 : Copolymerization mechanism of AN and AA.

Figure 3.3 : Experimental setup for synthesis of P(AN-co-AA).

Reaction carried on for 1.5 hour. Experimental setup of the polymerization was

demonstrated in Figure 3.3. The composed polymer was washed with dilute aqueous

19

HNO3 solution, water and ethanol consecutively. Copolymer was dried at 25°C for

24h. Polymerization yield for process having AA/AN ratio of 5/95 was calculated as

50%.

3.3 Preparation of P(AN-co-AA)/PPy Composite Films

0.25g P(AN-co-AA) (2.67%mole of final AA content by NMR measurement,) was

dissolved in Dimethylformamide (DMF) at 98°C and mixed for 10 hours. Py and

NPhPy were shown in Figure 3.5. After Py (i.e., 0.72, 1.44, 2.16, 2.88 mmoles) was

introduced into the solution, mixture was stirred for 1 hour at 25°C. Then, for the

formation of free-radical, CAN (30% amount of Py) was added as an oxidant and

temperature was increased to 80°C, stirring carried on until a viscous solution was

obtained following the solvent casting of the viscous solution as film on 5 x 5 cm2

glass substrate area at about 1 mm height (Figure 3.4).

Figure 3.4 : Procedure for P(AN-co-AA)/PPy and P(AN-co-AA)/PNPhPy composite

film formation.

Homogeneous viscous film was dried under 760 mmHg and 50°C. In oxidative

polymerization of NPhPy on P(AN-co-AA) matrix the same procedure was applied.

20

The film thicknesses (≈ 80-130 µm) was measured with Mitutoyo Digimatic Outside

Micrometer (MDC-25SB).

Figure 3.5 : Pyrrole (Py) and N-Phenyl pyrrole (NPhPy).

Figure 3.6 : Polymerization mechanism of PPy [30].

21

3.4 Preparation of Nanofibers of P(AN-co-AA)/PPy Composites

1g of P(AN-co-AA) (Including initially feed AA/AN ratio of 5/95) was dissolved in

Dimethylformamide (DMF) at 98°C and mixed for 10 hours. After Py and NPhPy

(0.72 mmoles) was introduced into the solution, mixture was stirred for 1 hour at

25°C. Water bath was used to set the temperature and provide homogeneous heat

transfer. Then, for the formation of free-radical, CAN (30% amount of Py) was

added as an oxidant and the mixture was stirred for 2 hours at 25°C. To acquire a

viscous solution, temperature was increased to 80°C, stirring carried on until a

viscous solution was achieved, afterwards it was put into a syringe with the diameter

of 12mm. Electrospinning apparatus was shown in figure 3.4. The weight ratio of

copolymer in DMF for pure P(AN-co-AA) was ≈25%. P(AN-co-AA)/PPy and

P(AN-co-AA)/PNPhPy composites included ≈50% by w/w.

Weight ratio of P(AN-co-AA) %

The distance between the electrodes was 10 cm. The applied voltage was 16 kV, 17

kV and 12 kV for P(AN-co-AA), P(AN-co-AA)/PPy and P(AN-co-AA)/PNPhPy

composites respectively. Rate of feed for pure P(AN-co-AA) was 1ml/h; for P(AN-

co-AA)/PPy and P(AN-co-AA)/PNPhPy composites were 0.5ml/h.

Figure 3.7 : Experimental setup of electrospinning [31].

22

3.5 Synthesis of PPy

Polymerization of Py monomer was performed without copolymer matrix in DMF

medium. 2ml of Py was dissolved in 100ml of DMF at 25°C and the mixture was

stirrred for 15 minutes. Then, 0.5802g CAN was introduced into the solution. As

soon as the initiator was added, the temperature was set to 80°C. Water bath was

used to set the temperature and provide homogeneous heat transfer. Reaction

continued for 2 h. Then DMF in the mixture was evaporated and the particles in the

mixture was washed with dilute HNO3, water and methanol respectively to purify

PPy from CAN, DMF and Py monomer. PPy was dried at 50°C for 24h. During PPy

was being washed with methanol for separation from the monomer, methanol

partially dissolved PPy. After methanol and Py were evaporated with Heidolph

Rotary Evaporator at 55 mmHg and 95°C, 1H NMR in deuterated

dimethylsulphoxide (DMSO-d6) of this PPy was measured. However, PPy which

remained above the filter after washing with HNO3, water and methanol, was

partially soluble in DMSO and not soluble in methanol. Polymerization efficieny was

calculated to % 4.

3.6 Characterization of P(AN-co-AA), Composite Films and Nanofibers

FTIR analysis of P(AN-co-AA), composite films and nanofibers were carried out

with FTIR-ATR reflectance spectrophotometer (Perkin Elmer, Spectrum One, with a

Universal ATR attachment with a diamond and ZnSe crystal) (Figure 3.8).

Figure 3.8 : Perkin Elmer, Spectrum One FTIR-ATR Spectrophotometer.

23

UV-Visible measurements were performed with UV-Visible spectrophotometer

(Perkin Elmer, Lambda 45) (Figure 3.9).

Figure 3.9 : Perkin Elmer, Lambda 45 UV-Visible Spectrophotometer.

Nuclear Magnetic Resonance measurements were performed with 250 MHz Brucker

AC Aspect 3000 using 1H NMR (Figure 3.10).

Figure 3.10 : 250 MHz Brucker AC Aspect 3000 NMR spectrometer [32].

Real permittivity, imaginary permittivity and conductivity measurements of

composite films were executed with Novocontrol broadband dielectric spectrometer

(Alpha-A High Performance Frequency Analyzer, frequency domain 0.001Hz to 3

GHz) at 25°C (Figure 3.11). Samples were fixed between two copper electrodes with

diameters of 20 mm (Figure 3.12).

24

Figure 3.11 : Novocontrol broadband dielectric spectrometer.

Figure 3.12 : Placing film samples between electrodes on Novocontrol broadband

dielectric spectrometer.

Thermogravimetric analysis (TGA) were made with TA, TGA Q50 with a heating

rate of 20°C/min. Differential Scanning Calorimeter (DSC) measurement was

operated with DSC TA Q10 with 3 cycles. Scanning Electron Microscope images of

nanofibers were obtained with Mini-SEM (SEC, SEN-3000M) (Figure 3.13).

Nanofiber diameters were measured with Adobe Acrobat 8 Professional.

25

Figure 3.13 : Mini-SEM, SEC, SEN-3000M.

3.7 Results and Discussion

3.7.1 FTIR-ATR spectrophotometric analysis

3.7.1.1 FT-IR calibration curve for P(AN-co-AA) pellet

KBr pellets of P(AN-co-AA) including 2.67 % AA segments calculated by NMR

measurements and blends of having 5 different ratios of PAN/PAA were preapared.

KBr pellets were compressed with hydraulic press under 10 tons/cm2 for 10s,

afterwards compression was quickly released. FT-IR measurements were operated

with transmission mode (Figure 3.14).

4000 3500 3000 2500 2000 1500 1000 500

cm-1

Pellet 5

Tra

nsm

itta

nce %

Pellet 4

Pellet 3

Pellet 2

Pellet 1

1725 cm-1

1725 cm-1

1725 cm-1

2243cm-1

2243cm-1

2243cm-1

2243cm-1

2243cm-1

1725 cm-1

Pellet P(AN-co-AA)

2243cm-1

Figure 3.14 : Figure FT-IR of KBr pellets of synthesized P(AN-co-AA) and blends

including varying ratio of PAA and PAN in transmission mode.

26

For constitution of calibration curve for blends including varying ratios of

PAN/PAA, graph of log(T0/T) vs. concentration (C) was drawn (Figure 3.15). T was

the transmittance value of CN stretching of PAN segments at 2243cm-1

. CPAN was

the concentration of PAN in the blends by mole%. Table of C and log(T0/T) was

shown in Table 3.1 and the calibration curve of blends was due. C=O stretching

vibration belonging to PAA at 1725cm-1

segments can also be shown in Figure 3.14.

Pellet No CPAN (mole%) log(T0/T)

1 0.2492 0.8409

2 0.4370 0.5895

3 0.6624 0.5031

4 0.8445 0.4918

5 1.0 0.2052

P(AN-co-AA) 0.6078

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

log (

T0 / T

)

CPAN

(mole%)

y = -0.7078x + 0.9781

R2 = 0.8427

Figure 3.15 : Calibration curve for blends of PAN and PAA including varying CPAN.

Equation y = -0.7078x + 0.9781 with R2 =0.8427 was obtained for calibration curve

(Figure 3.15). From this equation, unknown CPAN could be found by replacing y

value with log(T0/T) of P(AN-co-AA) pellet. Thus, as it was seen in Table 3.1,

log(T0/T) value of P(AN-co-AA) pellet was achieved to be 0.6078, which gave the

concentration of AN segments in the copolymer, CAN, as 0.5232. So, CAA was

0.4768.

3.7.1.2 P(AN-co-AA)

FTIR-ATR spectrum of P(AN-co-AA) were given in Figure 3.16 2939 cm-1

, 2243

cm-1

, 1452 cm-1

and 1720 cm-1

peaks respectively referred to CH bending, C≡N

Table 3.1: C(mole%) of PAN in PAN/PAA blends and log(T0/T) values at 2243cm-1

.

27

stretching and CH stretching of PAN segments and carboxyl C=O stretching of PAA

segments. Peak assignments were consistent with literature [9-10]. P(AN-co-AA)

with different feed ratio of AA/AN were seen in Figure 3.17; the peak belonging to

carboxyl C=O group at 1720 cm-1

was rising as AN/AA ratio was descending.

4000 3600 3200 2800 2400 2000 1600 1200 800

0.01

0.02

0.03

0.04

0.05

0.06 P(AN-co-AA)(95-5 w%)

PAN

2939 cm-1

2243 cm-1

1720 cm-1

1452 cm-1

Ab

so

rba

nce

cm-1

Figure 3.16 : FTIR-ATR Characterization PAN (Aldrich) and P(AN-co-AA).

4000 3600 3200 2800 2400 2000 1600 1200 8000.00

0.01

0.02

0.03

0.04

0.05

0.06

C=O Stretching (PAA)

1720 cm-1

CN Stretching (PAN)

2243 cm-1

CH Bending (PAN)

1453 cm-1

% 95-5 (AN / AA)

% 90-10 (AN / AA)

% 80-20 (AN / AA)

% 60-40 (AN / AA)

A

Frequency (cm-1)

Figure 3.17 : FTIR-ATR Characterization P(AN-co-AA) with different AN/AA

ratios.

28

3.7.1.3 P(AN-co-AA)-PPy and P(AN-co-AA)-PNPhPy composite films

In Figure 3.19 and Figure 3.20, FTIR-ATR analysis of PPy and PNPhPy including

and not including composite films were indicated. Sequentially 2939 cm-1

, 2243 cm-

1, 1452 cm

-1 and 1720 cm

-1 peaks were related with CH bending, C≡N stretching and

CH stretching of PAN and carboxyl (C=O) stretching of PAA. Furthermore, C=O

stretching, the characteristic peak of DMF at 1660 cm-1

shifted to 1663 cm-1

, in the

case the composite film without PPy showing DMF still existed after drying of the

film, which could be attributed to the interaction between the amide group of DMF

and nitrile group of PAN [33] segments of the copolymer (Figure 3.18). It could be

seen that, C=O stretching which was the characteristic peak of DMF at 1660 cm-1

shifted to 1646 cm-1

, in case composite films comprised PPy, which might be related

to intermolecular ionic interaction between partially negative C=O group of DMF

and partially positive NH group of PPy. Likewise, this peak shifted from 1660cm-1

to

1649cm-1

when films included PNPhPy showing that the interaction between DMF

was stronger with PPy than PNPhPy. Moreover, C=O stretching of PAA segments

shifted from 1720cm-1

to 1715cm-1

with the addition of rising PPy or PNPhPy

content into the composite films. Therefore, PPy and PNPhPy existed in strong

interactions with PAA segments in P(AN-co-AA). Furthermore, CN stretching

vibration of PPy and PNPhPy at 1452 cm-1

was observed in composite films. The

results were consistent with the literature [17]. The ratio of the absorbance values of

CN stretching of PPy and PNPhPy to C≡N stretching of PAN segments was

increasing as initially added Py and NPhPy was rising up. Thus, intermolecular

interaction between PPy, PNPhPy, P(AN-co-AA) and DMF could be seen form FT-

IR results and tentative mechanism for this interaction was demonstrated in Figure

3.18.

29

Figure 3.18 : Tentative mechanism for intermolecular interaction between P(AN-co-

AA), PPy chains and DMF.

4000 3600 3200 2800 2400 2000 1600 1200 800

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.00 0.72 1.44 2.16 2.881.6

2.0

2.4

2.8

3.2

3.6

4.0

4.4 CN Ring Stretching (1452cm

-1)

/CN Stretching (2243cm-1)

Ab

sro

ba

nce

(1

45

2cm

-1/2

24

3cm

-1)

Ra

tio

Initially Added Pyrrole (mmoles)

1452-1438 cm-1

1720-1715 cm-1

1663-1646 cm-1

2243 cm-1

P(AN-co-AA)/NoPy

P(AN-co-AA)/PPy (0.72mmoles)

P(AN-co-AA)/PPy (1.44mmoles)

P(AN-co-AA)/PPy (2.16mmoles)

P(AN-co-AA)/PPy (2.88mmoles)

Absorb

ance

cm-1

Figure 3.19 : FTIR-ATR Characterization of P(AN-co-AA) films and PPy including

P(AN-co-AA) films.

30

4000 3600 3200 2800 2400 2000 1600 1200 800

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.00 0.72 1.44 2.16 2.88

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6 CN Ring Stretching (1452cm

-1)

/CN Stretching (2243cm-1)

Ab

sro

ba

nce

(1

45

2cm

-1/2

24

3cm

-1)

Ra

tio

Initially Added N-phenylpyrrole (mmoles)

1452-1451 cm-1

1720-1715 cm-1

1663-1649 cm-1

2243 cm-1

P(AN-co-AA)/NoPNPhPy

P(AN-co-AA)/PNPhPy (0.72mmoles)

P(AN-co-AA)/PNPhPy (1.44mmoles)

P(AN-co-AA)/PNPhPy (2.16mmoles)

P(AN-co-AA)/PNPhPy (2.88mmoles)A

bsorb

ance

cm-1

Figure 3.20 : FTIR-ATR Characterization of P(AN-co-AA) films and PNPhPy

including P(AN-co-AA) films.

3.7.1.4 P(AN-co-AA), P(AN-co-AA)-PPy and P(AN-co-AA)-PNPhPy composite

nanofibers

CN stretching vibration of PPy, PNPhPy at 1452 cm-1

was observed in composite

nanofibers (Figure 3.21) [17]. The ratio of the absorbance values of CN stretching of

PPy and C≡N stretching of PAN segments was increasing as initially added Py was

rising up. In Figure 3.11, it can be seen that, C=O stretching which was the

characteristic peak of DMF at 1660 cm-1

shifted to 1647 cm-1

might be related to

intermolecular ionic interaction between partially negative C=O group of DMF and

partially positive NH group of PPy [33]. P(AN-co-AA) composite nanofibers

31

including PNPhPy showed same peaks as PPy comprising composites.

4000 3600 3200 2800 2400 2000 1600 1200 800

0.00

0.03

0.06

0.09

0.12

0.15

0.18

0.21

0.24

cm-1

1.65

1.70

1.75

1.80

1.85

1.90

1.95

2.00

P(AN-co-AA)

/PNPhPy

(0.72mmoles)

P(AN-co-AA)

/PPy

(0.72mmoles)

P(AN-co-AA)

CN Ring Stretching of PPy (1452cm-1)

/CN Stretching of PAN (2243cm-1)

Ab

so

rba

nce

(1

45

2cm

-1/2

24

3cm

-1)

Ra

tio

1452 cm-1

P(AN-co-AA)

P(AN-co-AA)/PPy (0.72mmoles)

P(AN-co-AA)/PNPhPy (0.72mmoles)

1647 cm-1

2937 cm-1

1720 cm-1

2243 cm-1

Ab

so

rba

nce

Figure 3.21 : FTIR-ATR characterization of P(AN-co-AA), P(AN-co-AA)/PPy and

P(AN-co-AA)/PNPhPy nanofibers.

3.7.2 UV-Visible spectrophotometric analysis

Thin film of 2.88 mmoles initially added pyrrole including P(AN-co-AA)/PPy was

treated with methanol, which turned into greenish color after 1 hour stirring at 40°C.

UV-Visible spectrophotometric measurement of greenish colored solution was

performed while methanol was taken as reference. An increase at the wavelength of

470 nm (Figure 3.22) was observed indicating low molecular weight PPy presence

[4].

32

300 400 500 600 700 800

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Ab

so

rba

nce

Wavelength (nm)

50 l Sol.

150 l Sol.

250 l Sol.

PPy (470 nm)

Figure 3.22 : UV-Visible absorbance vs. wavelength of solution of PPy in methanol.

3.7.3 Nuclear magnetic resonance measurements (NMR)

3.7.3.1 NMR of P(AN-co-AA)

Final composition of P(AN-co-AA) including 95/5 w/w ratio of initially fed AN and

AA was determined by 1H NMR spectroscopy (400 MHz, DMSO-d6, δ(ppm)).

Two strong peaks at δ=2.5065ppm and δ=3.6337ppm corresponded to

dimethylsulphoxide (DMSO) and the water in DMSO.

The chemical shifts for P(AN-co-AA) were indicated as δ=8.1268ppm (c, -COOH)

(Figure 3.23 and Figure 3.25), δ=2.0247ppm ( -CH2- belonging to PAN and PAA)

(Figure 3.23 and Figure 3.24). The degree of acrylic acid (DAA) was calculated with

the following equation [34]:

(3.1)

corresponds to the peak area of protons from carboxyl group (-COOH) of AA

segments, and indicated the peak area of protons from methylene

(-CH3) groups belonging to AA and AN segments in the copolymer respectively.

was shown in Figure 3.25 and calculated as 0.040; and

were shown in Figure 3.24 and was calculated as 2.991. Thus,

of copolymer was found to be 2.67 mole%. As, DAA(%) calculated from

33

NMR measurments and CAA, which was 0.4768, calculated from FT-IR calibration

curve were compared, CAA was higher than DAA. However, the polymerization

efficiency was 50% resulting 2.5g polymer. The reaction included initial feed of AA

as 0.25g (3.469x10-3

moles) and AN as 4.75g (8.952x10-2

moles) giving the initial

AA % by mole was 3.73%. This showed, even all of the acrylic acid was

incorporated into copolymerization, CAA in P(AN-co-AA) could not exceed 3.73%.

So, DAA (%) = 2.67% from NMR result was assumed to be the result for percentage

of AA segments in the copolymer.

Figure 3.23 : 1H NMR spectroscopy of P(AN-co-AA) in DMSO-d6 solvent (0.0-

10ppm).

Figure 3.24 : 1H NMR spectroscopy of P(AN-co-AA) in DMSO-d6 solvent (0.0-5.0

ppm).

34

Figure 3.25 : 1H NMR spectroscopy of P(AN-co-AA) in DMSO-d6 solvent (6.0-

10.0 ppm).

3.7.3.2 NMR of PPy

PPy is not soluble in DMSO [35]. In this study, PPy was synthesized in DMF

medium. After washing PPy with HNO3, water and methanol on filter paper, PPy

remained above the filter was partially dissolved in DMSO-d6 at 90°C for 0.5h.

However, this PPy was not soluble in methanol. 1H NMR in DMSO-d6 solvent of

PPy which was synthesized in DMF medium was shown in Figure 3.26. Three peaks

were observed at 7.0536, 7.2361 and 7.4163 indicating aromatic protons of PPy.

Figure 3.26 : 1H NMR spectroscopy of PPy in DMSO-d6 solvent.

3.7.4 Molecular weight determination

The viscosity average molecular weight of P(AN-co-AA) was calculated by the

Mark-Houwink equation [34]:

35

(3.2)

The intrinsic viscosity, [η] of the copolymer in DMF was determined by Ubbelodhe-

type viscometer (Figure 3.27) at 25 ± 0.3°C. C is the concentration of P(AN-co-AA)

in the solution. Relative viscosity ηr is the ratio t/t0 of flow times of solution and

solvent. Specific viscosity ηsp is ηr – 1. ηsp/C was plotted against C and data was

linearly regressed. y-intercept of the line was [η] (Figure 3.27).

Mark-Houwink parameters; K and α for the copolymer was found to be 2.78 x 10-4

g/dL and 0.76 respectively from the literature [34]. [η] was found to be 1.0101. From

Equation 3.2, = 48300.

Figure 3.27 : ηsp/C vs. C of the P(AN-co-AA) in DMF.

3.7.5 Dielectric and conductivity measurements

Conducting polymers constructed with short conjugation lengths, while electrical

conduction eventuates by charge hopping between two localized states between

polymeric chains [32]. A semiconductor and a dielectric material differ basically by

means of their band gap values. The dominant charge carriers in a semiconductor are

formed essentially by thermal excitation in the bulk owing to its small energy band

gap. However in a dielectric material, charge carriers are primarily coming from

electrical contacts or other external sources due to its energy band gap is relatively

large as compared with a semiconductor. Hence, a higher amount of energy is

required for band to band transitions in a dielectric material comparing with a

y = 0,0956x + 1,0101R² = 0,9388

1,063

1,068

1,073

1,078

1,083

1,088

0,59 0,64 0,69 0,74 0,79 0,84

ηsp

/ C

C (g/dL)

36

semiconductor. Real permittivity is one of the most significant electrical properties

of dielectric materials which is strongly related with frequency of the alternating

electric field [33].

10-2

10-1

100

101

102

103

104

105

106

107

0,0

1,0x10-5

2,0x10-5

3,0x10-5

4,0x10-5

5,0x10-5

6,0x10-5

7,0x10-5

8,0x10-5

10-2

10-1

100

101

102

103

104

105

106

107

0,0

1,0x10-5

2,0x10-5

3,0x10-5

4,0x10-5

5,0x10-5

6,0x10-5

7,0x10-5

8,0x10-5

P(AN-co-AA)

P(AN-co-AA)/PNPhPy (1.44 mmoles)

P(AN-co-AA)/PNPhPy (0.72 mmoles)

Co

nd

uctivity (

S/c

m)

Frequency (Hz)

a

P(AN-co-AA)

P(AN-co-AA)/PNPhPy (1.44 mmoles)

P(AN-co-AA)/PNPhPy (0.72 mmoles)b

Co

nd

uctivity (

S/c

m)

Frequency (Hz)

Figure 3.28 : a. Conductivity (S/cm) values of P(AN-co-AA) and P(AN-co-

AA)/PNPhPy films (For 0.72 and 1.44 mmoles of initially added

NPhPy) b. Conductivity (S/cm) values of P(AN-co-AA), P(AN-co-

AA)/PPy and P(AN-co-AA)/PNPhPy films (For 1.44 mmoles of

initially added Py and NPhPy).

37

10-2

10-1

100

101

102

103

104

105

106

107

100

101

102

103

104

105

106 P(AN-co-AA)

P(AN-co-AA)/PNPhPy (0.72 mmoles)

P(AN-co-AA)/PNPhPy (1.44 mmoles)

Re

al P

erm

ittivity (

Ep

s')

Frequency (Hz)

a

10-2

10-1

100

101

102

103

104

105

106

107

10-1

100

101

102

103

104

105

106

107 P(AN-co-AA)

P(AN-co-AA)/PNPhPy (0.72 mmoles)

P(AN-co-AA)/PNPhPy (1.44 mmoles)

Ima

gin

ary

Pe

rmittivity (

Ep

s")

Frequency (Hz)

b

Figure 3.29 : a. Real permittivity (Eps’) and b. imaginary permittivity (Eps”) of

P(AN-co-AA) and P(AN-co-AA)/PNPhPy films (For 0.72 and 1.44

mmoles of initially added NPhPy).

Conductivity and dielectric measurements were performed between 102-10

7 Hz at

25°C. In all samples, real permittivity (Eps’) and imaginary permittivity (Eps”)

decreased as the frequency (f) increased; beginning from 10 Hz to 107 remained

stable. In all composite films, conductivity values did not vary up to 104 Hz,

while over this frequency they were increased. In our measurements, P(AN-co-

AA) composite films had low frequency conductivity of 2.2x10-9

S/cm, while

P(AN-co-AA) films including 1.44 mmoles of PPy and PNPhPy had conductivity

of 9.3x10-9

S/cm and 1.6x10-8

S/cm respectively (Figure 3.27). Cetiner et al [33]

38

reported that, at 107 Hz, pure PAN composite film had conductivity value of

1.2x10-7

S/cm, PAN film including 1.44 mmoles of PPy has shown the

conductivity of 5.0x10-7

S/cm. In this study, conductivity values of P(AN-co-AA)

and 1.44 mmoles of PPy and PNPhPy containing P(AN-co-AA) composite films

were observed as 1.9x10-5

S/cm, 3.3x10-5

S/cm and 7.7x10-5

S/cm sequentially at

this frequency. Thus, PAA segments in composite films had significant effect on

conductivity values.

10-2

10-1

100

101

102

103

104

105

106

107

0,0

2,0x105

4,0x105

6,0x105

8,0x105

1,0x106

1,2x106

10-2

10-1

100

101

102

103

104

105

106

107

0,0

5,0x105

1,0x106

1,5x106

2,0x106

2,5x106

3,0x106

P(AN-co-AA)

P(AN-co-AA)/PPy (1.44 mmoles)

P(AN-co-AA)/PNPhPy (1.44 mmoles)

Re

al P

erm

ittivity (

Ep

s')

Frequency (Hz)

b

a

P(AN-co-AA)

P(AN-co-AA)/PPy (1.44 mmoles)

P(AN-co-AA)/PNPhPy (1.44 mmoles)

Ima

gin

ary

Pe

rmittivity (

Ep

s")

Frequency (Hz)

Figure 3.30 : a. Real permittivity (Eps’) and b. Imaginary permittivity (Eps”) of

P(AN-co-AA), P(AN-co-AA)/PPy and P(AN-co-AA)/PNPhPy films

(For 1.44 mmoles of initially added Py and PhPy).

At low frequencies Eps’ had high values (Figure 3.29 and Figure 3.30) as a result of

interfacial polarization meaning that charges growing on the boundaries at interfaces

39

inside bulk samples. This situation is the consequence of dispersion of islands of

conductive regions in the polymer inside an insulating polymer matrix according to

Rocha et al. [33,38]. At low frequency values, the side groups or small units of main

chain might have the tendency of following the variation of the electric field which

assist polarization [38]. As phenyl-substituted PPy had much more polar character

than PPy, dielectric permittivity values of PNPhPy were higher than those of PPy.

However at high frequencies, those small units and side groups such as phenyl

groups lack their capacity of moving along the field, lessens the contribution to the

polarization [38]. Opposing of charges defines the amount of dipole moment and

polarizability is a property of linkage between dipole moment and electric field [30].

Our composites had zero dielectric loss beyond 1 kHz pointing out they were lossless

at high frequencies, also dielectric constant showed resembling behavior.

It was observed that inclusion of phenyl substituents led to a decrease in the band gap

[39] as PNPhPy including composites had higher conductivities. The frequency

dependent dielectric constant at room temperature is due to interfacial space charge

(Maxwell Wagner) polarization leading to the high value of dielectric constant [33].

According to the conductivity results in composite films, it can be observed that high

conjugation of conjugated polymeric chains can be obtained in the presence of

phenyl groups due to additional phenyl ring conjugations compared to hydrogen

substitution.

40

10-2

10-1

100

101

102

103

104

105

106

107

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

10-2

10-1

100

101

102

103

104

105

106

107

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

P(AN-co-AA)

P(AN-co-AA)/PNPhPy (0.72mmoles)

P(AN-co-AA)/PNPhPy (1.44mmoles)

b

Mo

du

lus"

(M")

Frequency (Hz)

a

P(AN-co-AA)

P(AN-co-AA)/PNPhPy (0.72mmoles)

P(AN-co-AA)/PNPhPy (1.44mmoles)

Mo

du

lus' (M

')

Frequency (Hz)

Figure 3.31 : a. Modulus’ (M’) and b. Modulus” (M”) of P(AN-co-AA) and P(AN-

co-AA)/PNPhPy films (For 0.72 and 1.44 mmoles of initially added

NPhPy).

As it was shown in Figure 3.31(a) and Figure 3.32(a), M’ represented low values at

low frequencies (10-2

Hz), approaching to 10-7

Hz, pointing out to electrode

polarization negligibly making assistance to M’. Furthermore, M’ increased with

frequency, because of the lack of restoring force which is responsible from the

mobility of charge carriers exposing to an induced electric field [40].

41

10-2

10-1

100

101

102

103

104

105

106

107

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

10-2

10-1

100

101

102

103

104

105

106

107

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

b

P(AN-co-AA)

P(AN-co-AA)/PPy (1.44mmoles)

P(AN-co-AA)/PNPhPy (1.44mmoles)

Mo

du

lus"

(M")

Frequency (Hz)

a

P(AN-co-AA)

P(AN-co-AA)/PPy (1.44mmoles)

P(AN-co-AA)/PNPhPy (1.44mmoles)

Mo

du

lus' (M

')

Frequency (Hz)

Figure 3.32 : a. Modulus’ (M’) and b. Modulus” (M”) of P(AN-co-AA), P(AN-co-

AA)/PPy and P(AN-co-AA)/PNPhPy films (For 1.44 mmoles of

initially added Py and PhPy).

According to Figure 3.31 and Figure 3.32, as the frequency increased M’ and M”

increased to a maximum. In Figure 3.31(b) and Figure 3.32(b), a peak was observed

in the transition region from DC to AC conductivity M” curve showed a peak. This

peaks also shifted to higher frequencies due to increasing initially fed N-phenyl

pyrrole amount; and composite films including PNPhPy also exhibited M” peak at

higher frequency as compared with PPy. While conductivity value of P(AN-co-

AA)/PNPhPy composite films were higher P(AN-co-AA)/PPy, faster movement of

charge carriers signifying lower relaxation time [41]. Moreover, P(AN-co-AA)

composites containing 1.44mmoles of NPhPy also exhibited M” peak at higher

frequency due to higher conductivity.

42

0,0 5,0x10-2

1,0x10-1

1,5x10-1

0,0

1,0x10-2

2,0x10-2

3,0x10-2

4,0x10-2

0,0 5,0x10-2

1,0x10-1

1,5x10-1

0,0

1,0x10-2

2,0x10-2

3,0x10-2

4,0x10-2

a

P(AN-co-AA)

P(AN-co-AA)/PPy (1.44mmoles)

P(AN-co-AA)/PNPhPy (1.44mmoles)

Mo

du

lus"

(M")

Modulus' (M')

b

P(AN-co-AA)

P(AN-co-AA)/PNPhPy (0.72mmoles)

P(AN-co-AA)/PNPhPy (1.44mmoles)

Mo

du

lus"

(M")

Modulus' (M')

Figure 3.33 : Modulus’ (M’) vs. Modulus” (M”) of P(AN-co-AA), P(AN-co-

AA)/PPy and P(AN-co-AA)/PNPhPy films (For 1.44 mmoles of

initially added Py and PhPy).

In Figure 3.33, M’ vs. M” graphs (complex planes of electric modulus) of P(AN-co-

AA), P(AN-co-AA)/PPy and P(AN-co-AA)/PNPhPy composite films were

demonstrated. Curves represented a shape like distorted arc beginning from the

origin and ending in various M” values due to frequency in the range of 10-2

to 105,

which were not semicircles suiting to idealized Debye model [40].

In addition, the electrical properties of alkyl pyrroles are found to be dependent on

alkyl chain length and known that the presence of alkyl pyrroles efficiency on

electrical properties [33,42]. According to the fluorescence measurements of N-

43

phenyl pyrrole conjugated monomer in argon/acetonitrile matrix, it is determined that

vertical angle (90°) situation of phenyl and pyrrole rings to each other in a highly

polar environment may be required minimum energy [33,43].

3.7.6 Thermogravimetric analysis measurements (TGA)

TGA thermograms of pure P(AN-co-AA) having DAA of 2.67 mole%, PPy which

was synthesized in DMF without copolymer matrix, and P(AN-co-AA)/PPy

composite film were shown in Figure 3.34 and Figure 3.35.

100 200 300 400 500

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

P(AN-co-AA)

@450oC

P(AN-co-AA)

@385oC

PPy

@191oC

P(AN-co-AA)

@311oC

P(AN-co-AA)

PPy

P(AN-co-AA)/PPy (1.44mmoles)

De

riva

tive

We

igh

t (%

We

igh

t/m

in)

Temperature ( oC )

DMF

@163oC

PPy

@265oC

P(AN-co-AA)

@300oC

Figure 3.34 : Temperature vs. Derivative Weight (%Weight/min) from TGA of

P(AN-co-AA), PPy and P(AN-co-AA)/PPy composite film including

1.44 mmoles initially fed Py.

Degradation of polymers and DMF solvent can be analyzed clearly from derivative

weight vs. temperature graph (Figure.3.34). DMF disappearance at 163°C in P(AN-

co-AA)/PPy composite film, which is above the boiling point of pure DMF, can be

attributed to intermolecular interaction between copolymer matrix, DMF and PPy.

PPy synthesized in DMF without P(AN-co-AA) matrix indicated degradation at

191°C. However, PPy presented in P(AN-co-AA)/PPy composite revealed the

degradation at 265°C which may also be due to the hydrogen bonding between PPy

chain, copolymer matrix and DMF. AN and AA segments in pure copolymer

exhibited weight loss at 300°C and 295°C respectively. AA segments indicated

44

degradation at 385°C. AN and AA segments both indicated a weight loss at 450°C.

In literature P(AN-co-AA) used as membrane exhibited weight losses at 350°C and

410°C which is lower than the values in this study [5]. Pure PPy signified its major

weight loss at 210°C which is a higher value than the PPy synthesized in DMF

medium without copolymer matrix, whilst lower than the PPy degradation concerned

with P(AN-co-AA)/PPy composite film. Also pure PAN nanofiber started its weight

loss at 310°C [44]. PAA chains showed weight loss at 290°C due to anhydride

formation and 420°C due to polymer degradation [45]. PPy synthesized in DMF

medium without copolymer matrix generally showed a gradual weight loss, whilst

P(AN-co-AA) exhibited discrete weight losses. Thus, in P(AN-co-AA)/PPy

composite film not only appeared gradual weight loss, but also discrete losses

(Figure 3.35). Results showed that intermolecular interaction between copolymer

matrix, PPy and DMF (Figure 3.18) stabilized the composite film towards higher

degradation temperatures of the components as compared to their individual

degradation temperatures.

100 200 300 400 500 600

40

50

60

70

80

90

100 P(AN-co-AA)

PPy

P(AN-co-AA)/PPy (1.44mmoles)

% W

eig

ht

Temperature (oC)

Figure 3.35 : Temperature vs. % Weight from TGA of P(AN-co-AA), PPy and

P(AN-co-AA)/PPy composite film including 1.44 mmoles initially fed

Py.

45

3.7.7 Differential scanning calorimetry measurement (DSC)

Differential Scanning Calorimeter (DSC) measurement of P(AN-co-AA) including

2.67 AA by % moles was operated with 3 cycles. First cycle was heating from -30°C

to 150°C, second cycle was cooling from 150°C to -30°C and third cycle was heating

from -30°C to 250°C. Third cycles were considered for DSC analysis. Heating rate

was 10°C/min. Tg of P(AN-co-AA) including 2.67 AA by % mole, from NMR

measurement, was calculated as 101.14°C (Figure 3.36). This value was lower than

130°C Tg value of a blank copolymer membrane of AN and AA [5]. Although, it was

a higher value than Tg = 85°C of commercial PAN [45]. showing AA segments in

P(AN-co-AA) gained a more stable structure to copolymer.

Figure 3.36 : DSC of P(AN-co-AA) including 2.67 AA by % mole.

3.7.8 Scanning electron microscope measurements (SEM)

The weight ratio of copolymer in DMF for pure P(AN-co-AA) was ≈25%. P(AN-co-

AA)/PPy and P(AN-co-AA)/PNPhPy composites included ≈50% by w/w. Because,

lower weight ratio of P(AN-co-AA) in P(AN-co-AA)/PPy and P(AN-co-

AA)/PNPhPy nanofibers could not be achieved due to low viscosities. The distance

between the electrodes was 10 cm. The applied voltage was 16 kV, 17 kV and 12 kV

for P(AN-co-AA), P(AN-co-AA)/PPy and P(AN-co-AA)/PNPhPy nanofibers

Tg = 101.14°C

-1.4

-1.2

-1.0

-0.8

-0.6

He

at

Flo

w (

W/g

)

-10 10 30 50 70 90 110 130 150 170 190

Temperature (°C)

––––––– P(AN-co-AA) (2.67 AA %mole)

Exo Up Universal V3.9A TA Instruments

46

consecutively. Rate of feed for pure P(AN-co-AA) was 1ml/h; for P(AN-co-AA)/PPy

and P(AN-co-AA)/PNPhPy composites were 0.5ml/h. Scanning electron microscope

(SEM) images of nanofibers were taken.

As it was seen in Figure 3.37, beads were observed in SEM image of P(AN-co-AA)

nanofiber. x1000 magnification was applied. The sample was without gold coating.

For higher magnification, sample can be coated with gold supplying the sample

conductivity. Also, beads were observed in Figure 3.37 due to processing conditions

such as viscosity of the solution, applied voltage and the distance between the

electrodes.

Figure 3.37 : SEM images of nanofibers of pure P(AN-co-AA).

SEM images of P(AN-co-AA)/PPy nanofibers were shown in Figure 3.38 and 3.39

with magnification of x1500 and x3000 respectively. Less beads were observed than

P(AN-co-AA) nanofiber and higher magnification much clearly without gold

coating. This can be attributed to higher conductivity of P(AN-co-AA) with respect

to P(AN-co-AA).

47

Figure 3.38 : SEM images of nanofibers of P(AN-co-AA)/PPy composite with

magnification of x1500.

Figure 3.39 : SEM images of nanofibers of P(AN-co-AA)/PPy composite with

magnification of x3000.

Average diameter of P(AN-co-AA)/PPy nanofibers were measured. Narrow

distribution of nanofibers were observed giving highest value for ≈180 nm (Figure

3.40).

48

150 200 250 300 350 400 450 5000

5

10

15

20

25

30

35

40

45

50

55

Fre

qu

en

cy (

%)

Nanofiber Diameter (nm)

Figure 3.40 : Nanofiber diameter distribution of P(AN-co-AA)/PPy composite.

SEM images of P(AN-co-AA)/PNPhPy nanofibers were shown in Figure 3.41 and

3.42 with magnification of x1000 and x5000 respectively. Less beads were observed

than P(AN-co-AA) and P(AN-co-AA)/PPy nanofibers and higher magnification

much clearly without gold coating. This can be attributed to higher conductivity of

P(AN-co-AA) with respect to P(AN-co-AA) and P(AN-co-AA)/PPy.

Figure 3.41 : SEM images of nanofibers of P(AN-co-AA)/PNPhPy composite with

magnification of x1000.

49

Figure 3.42 : SEM images of nanofibers of P(AN-co-AA)/PNPhPy composite with

magnification of x5000.

Average diameter of P(AN-co-AA)/PNPhPy nanofibers were measured (Figure

3.43). Narrow distribution of nanofibers were observed giving highest value for ≈300

nm. Thus, nanofibers of P(AN-co-AA)/PNPhPy composites had higher diameter

values than P(AN-co-AA)/PPy. This case might be attributed to higher applied

voltage of P(AN-co-AA)/PPy nanofibers than P(AN-co-AA)/PNPhPy, while weight

ratio of P(AN-co-AA), feed rate (0.5 ml/h) and distance between the electrodes

(10cm) were the same. Also, considering the conductivity of composite films of

P(AN-co-AA)/PNPhPy was higher than P(AN-co-AA)/PPy, P(AN-co-AA)/PNPhPy

composite in the syringe might have overcome the surface tension of the liquid easier

and higher amount of composite material might have crossed over onto the collector

200 250 300 350 400 450 500 5500

5

10

15

20

25

30

35

Fre

eq

ue

ncy (

%)

Nanofiber Diameter (nm)

Figure 3.43 : Nanofiber diameter distribution of P(AN-co-AA)/PNPhPy composite.

50

51

4. CONCLUSION AND RECOMMENDATIONS

FTIR-ATR and UV-Visible spectroscopy results of composites clearly showed the

presence of PPy in the P(AN-co-AA) matrix indicating the successful reaction and

dispersion of PPy particles on matrix by the use of Ce(IV).

Dielectric spectroscopic measurements of composite films indicated that at low

frequencies eps’ had high values as a result of interfacial polarization meaning that

charges growing on the boundaries at interfaces inside bulk samples. This situation is

the consequence of dispersion of islands of conductive regions in an insulating

P(AN-co-AA) matrix. PAA segments in composite films had significant effect on

dielectric properties. Phenyl substitution enhanced conductivity and dielectric

properties of composites. Electromagnetic interference (EMI) shielding is important

in electronic and communication industries. So composites which had high dielectric

permittivity seemed to be very suitable materials for eliminating EMI shielding

applications. The electrical properties of alkyl pyrroles are found to be dependent

on alkyl chain length and the presence of alkyl pyrroles should have an effect on

electrical properties of composites. From NMR results, although P(AN-co-AA)

included little AA segments (2.67 % by mole), conductivity and dielectric

permittivity values was enhanced considerably as compared to PAN. According to

thermogravimetric analysis results, that intermolecular interaction between

copolymer matrix, PPy and DMF stabilized the composite film towards higher

degradation temperatures of the components as compared to their individual

degradation temperatures. DSC results showed AA segments in P(AN-co-AA),

gained a more stable structure to copolymer due to higher Tg value of P(AN-co-AA)

than commercial PAN. Nanofibers of P(AN-co-AA)/PNPhPy composites had higher

diameter values than P(AN-co-AA)/PPy which might be an indication of higher

conductivity value of P(AN-co-AA)/PNPhPy than P(AN-co-AA)/PPy composite

films

52

53

REFERENCES

[1] Frushour, B. G., and Knorr, R. S.; 1998: Handbook of Fiber Chemistry, 2nd

ed., pp. 875, Eds. Lewin M., Marcel Dekker, New York.

[2] Nuyken, O.; 1992: Handbook of Polymer Synthesis, Part A, pp. 277, Eds.

Kricheldorf H.R., New York.

[3] Rulison, C.; 1998: Water Soluble Polymers, Solution Properties and

Applications, pp. 6, Eds. Amjad Z., Plenum, New York.

[4] Kim, J.H., Kim, K.Y.; 1987: Permeation Characteristics of Solutes through

Water Swollen Polymeric Membranes: II. Copoly(acrylonitrile-acrylic

acid) Membranes. Polymer(Korea). Vol.11, pp. 71-80.

[5] Cristallini, C., Ciardelli, G., Barbani, N., Giusti, P.; 2004: Acrylonitrile-

Acrylic Acid Copolymer Membrane Imprinted with Uric Acid for

Clinical Uses. Macromoecular Bioscence. Vol.4, pp. 31-38.

[6] Shan, J. D., He, Y., Wang, S., Xue, H., Zheng, H.; 2006: A Porous

Poly(acrylonitrile-co-acrylic acid) Film-based Glucose Biosensor

Constructed by Electrochemical Entrapment. Analytical Biochemistry.

Vol.356, pp. 215-221.

[7] Wang, H.Y., Kobayashi, T., Fujii, N.; 1996: Molecular Imprint Membranes

Prepared by the Phase Inversion Precipitation Technique. Langmuir.

Vol.12, pp. 4850-4856.

[8] Aqil, A., Detrembleur, C., Gilbert, B., Jerome, R., Jerome, C.; 2007:

Controlled RAFT Synthesis of Polyacrylonitrile-b-poly(acrylic acid)

Diblocks as Precursors of Carbon Nanocapsules with Assistance of

Gold Nanoparticles. Chem. Mater. Vol.19, pp. 2150-2154.

[9] Moghadam, S.S., Bahrami, S.H.; 2005: Copolymerization of Acrylonitrile-

Acrylic Acid in DMF-Water Mixture. Iranian Polymer Journal. Vol.

14 , pp. 1032-1041.

[10] Shan, D., Cheng, G., Zhu, D., Xue, H., Cosnier, S., Ding, S.; 2009: Direct

Electrochemistry of Hemoglobin in Poly(acrylonitrile-co-acrylic acid)

and Its Catalysis to H2O2. Sensors and Actuators B. Vol.137, pp. 259-

265.

[11] Brar, A.S., Dutta, K.; 1998: Microstructure and Compositional Sequence

Determination of Acrylonitrile/Acrylic acid Copolymers by NMR

Spectroscopy. European Polymer Journal. Vol.34, pp. 1585-1597.

[12] Lee, Y., Shin, D., Cho, J., Park, Y.H., Son, Y., Baik, D.H.; 1998: Ionic

Interactions in Polyacrylonitrile/Polypyrrole Conducting Polymer

Composite. Journal of Applied Polymer Science.Vol.69, 2641-2648.

54

[13] Kumar, D., Sharma, R.C.; 1998: Advances in Conductive Polymers.

European Polymer Journal. Vol.34 , pp. 1053-1060.

[14] Wang, L.X., Li, X.G., Yang, Y.L.; 2001: Preparation, Properties and

Applications of Polypyrroles, Reactive and Functional Polymers.

Vol.47, pp. 125-139.

[15] Lee, C.Y., Lee, D.E., Joo, J., Kim, M.S., Lee, J.Y., Jeong, S.H., Byun,

S.W.; 2001: Conductivity and EMI Shielding Efficiency of

Polypyrrole and Metal Compounds Coated on(non) Woven Fabrics

Synthetic Metals, Vol.119, pp. 429-430.

[16] Kuhn, H.H., Child, A.D., Kimbrell, W.C.; 2000: Toward Real Applications of

Conductive Polymers, Synthetic Metals. Vol.71, pp. 2139-2142.[17]

Saville, P.; 2005: Polypyrrole Formation and Use, Defence R&D

Canada – Atlantic Defence Paul Saville Technical Memorandum

DRDC Atlantic TM.

[18] Dakin, T.W.; 2006: Conduction and Polarization Mechanisms and Trends in

Dielectrics, IEEE Electrical Insulation Magazine. Vol.22, pp. 11-28.

[19] Inzelt, G.; 2008: Conducting Polymers: A New Era in Electrochemistry, Eds.

Scholz, F., Springer, Leipzig, Germany.

[20] Blythe, T., Bloor, D.; 2005: Electrical Properties of Polymers, 2nd

Ed.,

Cambridge University Press, UK.

[21] Jones, W.; 1997: Organic molecular solids: properties and applications, CRC

Press, USA.

[22] Epstein, A.J.; 1999: Conductive Polymers and Plastics, pp. 7., Eds. Rupprecht

L., RTP Company Press; USA.

[23] Skotheim, T.A., Reynolds, J.R.; 2007: Handbook of Conducting Polymers, 3rd

Ed., Conjugated Polymers:Theory, Synthesis, Properties and

Characterization, CRC Press, USA.

[24] Kao, K.C.; 2004: Dielectric Phenomena in Solids,Elsevier, USA.

[25] Raju, G.G.; 2003: Dielectrics in Electric Fields, Marcel Dekker, USA.

[26] Wang, Z.G. Ke, B.B., Xu, Z.K.; 2007: Covalent Immobilization of Redox

Enzyme on Electrospun Nonwoven Poly(Acrylonitrile-co-Acrylic

Acid) Nanofiber Mesh Filled With Carbon Nanotubes: A

Comprehensive Study, Biotechnology and Bioengineering. Vol.97, pp.

708-720.

[27] Huang, X.J., Yu, A.G., Jiang, J., Pan, C., Qian, J.W., Xu, Z.K.; 2009:

Surface Modification of Nanofibrous Poly(acrylonitrile-co-acrylic

acid) Membrane with Biomacromolecules for Lipase Immobilization,

Journal of Molecular Catalysis B: Enzymatic. Vol.57, pp. 250-256.

[28] Ramakrishna, S., Fujihara, K., Teo, W.E., Lim, T.C., Ma, Z.; 2005: An

Introduction yo Electrospinning and Nanofibers, World Scientific

Publishing Co. Pte. Ltd., Singapore.

[29] Bhardwaj, N., Kundu, S.C.; 2010: Electrospinning: A fascinating fiber

fabrication technique, Biotechnology Advances. Vol.28, pp. 325-347.

55

[30] Wallace, G.G., Spinks, G.M., Keon-Maguire, L.A.P., Teasdale, P.R.; 2009:

Conductive Electroactive Polymers: Intelligent Polymer Systems, 3rd

Ed.; CRC Press, USA.

[31] Cetiner, S., Kalaoglu, F., Karakas, H., Sarac, A.S.; 2010: Electrospun

Nanofibers of Polypyrrole-Poly(Acrylonitrile-co-Vinyl Acetate),

Textile Research Journal. In press.

[32] Url-1 < http://www.kimya.itu.edu.tr/TR/nmr.php> accessed at 15.07.2010.

[33] Cetiner, S., Karakas, H., Ciobanu, R., Olariu, M., Kaya, N.U., Unsal, C.,

Kalaoglu, F., Sarac, A.S.; 2010: Polymerization of Pyrrole

Derivatives on Polyacrylonitrile Matrix, FTIR-ATR and Dielectric

Spectroscopic Characterization of Composite Thin Films, Synthetic

Metals, Vol.160, pp. 1189-1197.

[34] Fang, B., Ling, Q., Zhao, W., Ma, Y., Bai, P., Wei, Q., Li, H., Zhao, C.;

2009: Modification of polyethersulfone membrane by grafting bovine

serum albumin”on the surface of polyethersulfone/poly(acrylonitrile-

co-acrylic acid) blended membrane, Journal of Membrane Science,

Vol.329, pp. 46-55.

[35] Li, X.G., Wang, L.X., Jin, Y., Zhu, Z.L., Yang, Y.L.; 2001: Preparation and

Identification of a Soluble Copolymer from Pyrrole and o-Toluidine,

Journal of Applied Polymer Science, Vol.82, pp.510-518.

[36] Kaynak A.; 1998: Electrical Conductivity of Polypyrrole Films at a

Temperature Range of 70K to 350K, Materials Research Bulletin.

Vol.33, pp. 81-88.

[37] Papathanassiou, A.N., Grammatikakis, J., Sakellis, I., Sakkopoulos, S.,

Vitoratos, E., Dalas, E.; 2004: Low Frequency Dielectric Relaxation

Phenomena in Conducting Polypyrrole and Conducting Polypyrrole-

Zeolite Composites, Journal of Applied Physics, Vol.96, pp. 3883-

3888.

[38] Saafan, S.A., El-Nimr, M.K., El-Ghazzawy, E.H.; 2006: Study of Dielectric

Properties of Polypyrrole Prepared using Two Different Oxidizing

Agents, Journal of Applied Polymer Science, Vol.99, pp. 3370-3379.

[39] Henckens, A., Colladet, K. , Fourier, S., Cleij, T. J., Lutsen, L., Gelan, J.,

Vanderzande, D.; 2005: Synthesis of 3,4-Diphenyl-Substituted

Poly(Thienylene Vinylene), Low-Band-Gap Polymers via the

Dithiocarbamate Route, Macromolecules, Vol.38, pp. 19-26.

[40] Ai, L., Jiang, J., Li, L.; 2010: Frequency-dependent Dielectric and Electric

Modulus Properties of Li–Ni–Sm–Fe–O Spinel Embedded in

Conducting Polymer, Journal of Materials Science: Materials in

Electronics, Vol.21, pp. 206-2010.

[41] Migahed, M.D., Ishra, M., Fahmy, T., Barakat, A.; 2004: Electric Modulus

and AC Conductivity Studies in Conducting PPy Composite Films at

Low Temperature, Journal of Physics and Chemistry of Solids,

Vol.65, pp. 1121-1125.

[42] King, R.C.Y., Boussoualem, M., Roussel, F.; 2007: Spectroscopic and

Electrical Properties of 3-alkyl pyrrole-pyrrole, Copolymers, Polymer,

Vol.48, pp. 4047-4054.

56

[43] Schweke, D., Haas, Y.; 2003: The Fluorescence of N-Phenylpyrrole in an

Argon/Acetonitrile Matrix, Journal of Physical Chemistry. A.

Vol.107, pp. 9554–9560.

[44] Ji, L., Yao, Y., Toprakci, O., Lin, Z., Liang, Y., Shi, Q., Medford, A.J.,

Millns, C.R., Zhang, X.; 2010: Fabrication of Carbon Nanofiber-

Driven Electrodes from Electrospun Polyacrylonitrile/Polypyrrole

Bicomponents for High-performance Rechargeable Lithium-ion

Batteries, Journal of Power Sources, Vol.195, pp. 2050-2056.

[45] Çaykara, T., Güven, O.,; 1998: Effect of Preparation Methods on Thermal

Properties of Poly(acrylic acid)/Silica Composites, Journal of Applied

Polymer Science, Vol.70, pp. 891–895.

[46] Url-2 <http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N

4=181315|ALDRICH&N5=SEARCH_CONCAT_PNO|BRAND_KE

K&F=SPEC> accessed at 14.10.2010.

57

CURRICULUM VITA

Candidate’s full name: Nazif Uğur KAYA

Place and date of birth: Seyhan/ADANA, TÜRKĠYE, 09.12.1985

Permanent Address: CemalpaĢa Mah., Atatürk Cad., 1 Sok., Altın Apt., B Blok,

3/9, Seyhan/ADANA

Universities and

Colleges attended: Bachelor’s Degree: Istanbul Technical University, Chemical

Engineering (2003-2007)

Publications: Cetiner, S., Karakas, H., Ciobanu, R., Olariu, M., Kaya, N.U.,

Unsal, C., Kalaoglu, F., Sarac, A.S.; 2010: Polymerization of Pyrrole Derivatives

on Polyacrylonitrile Matrix, FTIR-ATR and Dielectric Spectroscopic

Characterization of Composite Thin Films, Synthetic Metals, Vol.160, pp. 1189-

1197.