research article fourier transform infrared spectral

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2013 Article ID 937284 5 pageshttpdxdoiorg1011552013937284

Research ArticleFourier Transform Infrared Spectral Analysis of Polyisoprene ofa Different Microstructure

Dongmei Chen1 Huafeng Shao2 Wei Yao2 and Baochen Huang2

1 High Performance Polymer Institute of Qingdao University of Science and Technology Qingdao 266042 China2 Key Lab of Rubber and Plastic Ministry of Education Qingdao University of Science and Technology Qingdao 266042 China

Correspondence should be addressed to Dongmei Chen cdm321126com

Received 4 April 2013 Accepted 22 May 2013

Academic Editor Zhou Yang

Copyright copy 2013 Dongmei Chen et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Some polyisoprene samples of differentmicrostructure contents were studied by Fourier transform infrared (FTIR) and 1HNuclearmagnetic resonance (1H NMR) On the basis of detailed analysis of FTIR spectra of polyisoprene the shift of absorption peakscaused by microstructure contentrsquos variation was discussed The contents of the polyisoprene samplesrsquo microstructure which wasdetermined by the 1H NMR was used as the standard Through the choice calculation and comparison with the correspondingabsorption peaks of FTIR a method based on the results of the analysis has been developed for the determination of themicrostructure contents of polyisoprene by FTIR

1 Introduction

As it is well known polyisoprene (PIp) is one kind of impor-tant rubbers and there are four kinds of microstructure in itsmolecular chain which are cis-14- trans-14- 12- and 34-polyisopreneThemain ingredient of nature rubber is cis-14-or trans-14-polyisoprene For example Hevea brasiliensis(the Brazilian rubber tree) is polyisoprene with more than5000 cis-14-repeat units except for the transinitiator residueof repeat units ranging from 1 to 4 depending on the plantspecies Gutta-percha Balata orMalaysian rubber is polyiso-prene with trans-14-repeat units [1ndash4] Since English chemistMichael Faraday found that the structure unit of naturerubber was C

5H8 the research of synthetic polyisoprene

keeps active [1ndash7]Except for the synthesis of high content of cis-14- or

trans-14-polyisoprene to imitate and replace nature rubberthe research on synthesis of polyisoprene with variablemicrostructure contents keeps attractive in order to obtainsome materials of special properties For example with 34-unit contentrsquos increasing the curing rate and low temperatureproperties of polyisoprene decrease but hardness and elas-ticity increase as well as tensile properties tension set and

tearing strength maintain are slightly changed Particularlythe water resistance and hermeticity of polyisoprene withhigh 34-unit content can compare with butyl rubber [8ndash11]The application of polyisoprene with high 34-unit content intread can improve the skidding resistance traction propertyand cutting growing resistance and also can decrease thegeneration of heat by friction So it is the new varieties ofrubber for a fuel-saving environmental protection and safetytire

Most of the studies on microstructure of polymers arecharacterized by nuclear magnetic resonance (NMR) spec-trophotometer and FTIR [12 13] The first extensive IRspectroscopic studies of synthetic polyisoprenes were under-taken by Binder Cornell and Koenig In comparison withother polymers much less work has been reported on poly-isoprene [14] In this paper polyisoprenes of some differ-ent microstructure content are analyzed by FTIR in de-tails Through comparison the intensity of correspondingmicrostructure characterization peak in FTIR with in NMRthe experience relation equation is founded and the methodof calculating the microstructure content of polyisoprene byFTIR is also established

2 International Journal of Polymer Science

2 Experimental

21 Materials All the polyisoprene samples with variablemicrostructure content were polymerized according to [15ndash18]

22 Characterization

221 FTIR Tensor 27 (Bruker German) has been used in theanalysis The samples are tested by ATR-FTIR with 4 cmminus1resolution and scanned 32 times

222 1H NMR AV500 (Bruker German) has been used inthe analysis 1H NMR spectra of the polyisoprene in CDCl

3

were obtained at 50013Hz and chemical shifts were referredto TMS

The 1H NMR spectrum of polyisoprene which contains14- 12- and 34-unit is shown in Figure 112057552sim5012057550sim48and 12057548sim46 peaks are ascribed to the olefinic hydrogen of14- 12- and 34-unit respectively Determining the intensityof these spectral lines then calculating 14- 12- and 34-unitcontent with formula (1) and the results are shown in Table 1

11988314-PIp

=int 12057552ndash50

int 12057552ndash50 + (int 12057550ndash48 + int 12057548ndash46) 2times 100

11988312-PIp

=int 12057550ndash482


11988334-PIp

=int 12057548ndash462


(1)

3 Results and Discussion

31 Analysis of FTIR Spectra of Polyisoprene Polyisoprenehas four kinds of microstructure which are cis-1 4- trans-14- 1 2- and 3 4-polyisoprene as shown in Figure 2

Figure 3 shows seven FTIR spectra of polyisoprene withdifferent microstructure content

The characterization and attribution peaks of FTIR spec-tra of polyisoprene are listed in Table 2

It can be seen from Figure 3 and Table 2 that the differ-ence of FTIR behavior of the polyisoprene microstructuresis obvious However only 910 888 and 840 cmminus1 peakscan be used for quantitative calculation of microstructurecontent of polyisoprene It is because that the peaks forquantitatively calculation must have moderate intensity littleinterfering factors by other peaks or conditions and so onExcept for those differences shown in Table 2 Table 3 showssome frequency excursion caused by microstructure contentchanging

0

50

100

150

20051345121

4966494649004875484247394670

056

057

026

100

t1 (ppm)450500550

Figure 1 1H NMR spectrum of polyisoprene

Table 1 Microstructure contents of polyisoprene by 1H NMR

Sample 14-mol 34-mol 12-molA 100 (cis-14) 0 0B 996 (trans-14) 02 02C 90 5 5D 53 24 23E 30 59 11F 24 63 13G 18 67 15

32 Quantization Calculation of Microstructure Content ofPolyisoprene by FTIR According to the Beer-Lambert lawthe integrated intensity 119860 of a characteristic band can beexpressed as follows

119860 = 119887119888int

+infin

0

120576 (]) 119889] (2)

Here 120576 is the absorption coefficient 119887 is the thickness 119888is the concentration and ] is the wavenumber

Choosing a peak which has moderate intensity and is notaffected by configuration conformation or other structurefactors as internal standard of thickness then formula (2) canbe changed to the following

[119860] =1198601

1198600

= 1198881[

[

int+infin

0120576 (1205991) 119889120599

1198880int+infin

0120576 (1205990) 119889120599

]

]

= 1198881sdot 119896 (3)

Here ldquo1rdquo means characteristic band and ldquo0rdquo meansinternal standard band ldquo119870rdquo is the correction factor and canbe calculated by 1HNMRdates As described above 910 888and 840 cmminus1 peaks can be used for quantitatively calculatingmicrostructure content of polyisoprene Table 2 shows thatthere is seldom peak which can meet the request of internalstandard peak In this paper 2727 cmminus1 is used as internalstandard peak The integrated intensity 119860 are calculated bythe software of FTIR and the integration methods are shownin Figure 4

International Journal of Polymer Science 3

CC C C

HC C

H

CH2 CH2

CH2CH2

CH3

CH2

CH3

CH2

CH2

n

n

n n

H2C

H3C

H3CCH

CH

12- 34- cis-14- trans-14-

Figure 2 The structural formula of polyisoprene

Table 2 The explanation of absorption peaks of FTIR spectrum of polyisoprene

Wavenumbercmminus1 Attribution Wavenumbercmminus1 Attribution

3080ndashCndashH stretching vibration ofcarbon-carbon double bond in

12-unit 1150 Stretching vibration of CC mainchain in trans-14-unit

3070 CH2 stretching vibration ofndashC=Cndash in 34-unit 1140 Stretching vibration of CC main

chain in cis-14-unit

3035 CH stretching vibration ofndashC=Cndash in 14- or 12-unit 1044 Stretching or wagging vibration

of CH3C=C in trans-14-unit

2727 Sympathetic vibration 1036 Stretching or wagging vibrationof CH3C=C in cis-14-unit

1663 C=C stretching vibration of14-unit 1003 Stretching vibration of CndashC in

34-unit

1644 C=C stretching vibration of34- or 12-unit 910

Out-of-plane bending vibrationof CH2 in the ndashCH=CH2

(12-unit)

1413Bending vibration of CndashH inthe =CH2 group of 34- or

12-unit888 Out-of-plane bending vibration

of CH2 in the ndashC=CH2 (34-unit)

1383 Scissoring vibration of CH3 intrans-14-unit 843

Out-of-plane bending vibrationof CndashH in the ndashCH=CHndash group

of trans-14-unit

1375 Scissoring vibration of CH3 incis-14- 34- and 12-units 837


of cis-14-unit

1325 Scissoring vibration of CH3 orCH in trans-14-unit 600 Torsion or twisting vibration of

CCC group in trans-14-unit

1311 Scissoring vibration of CH3 orCH in cis-14-unit

Table 3 The change of peaks of FTIR spectra according to the microstructure contents of polyisoprene

Explanationpeak value Spectrum A Spectrum B Spectrum C NoteMicrostructure content

34-unit 5 24 67 34-unit increase by progressively12-unit 5 23 15 12-unit increase by degrees14-unit 90 53 18 14-unit decrease by degrees

Dissymmetry stretching vibrationof ndashCH3

2962125 2964053 2965982 Blue shift of peak (the value is 2978 cmminus1 intrans-14-unit)

C=C stretching vibration 1644982 1644018 1643054 Red shift of peak

Scissoring vibration of CH3 1376925 1374997 1374033 Red shift of peak (the value is 1383 cmminus1 intrans-14-unit)

Out-of-plane bending vibration ofCH2 in the ndashC=CH2 (34-unit)

889023 888059 887095 Red shift of peak

Out-of-plane bending vibration ofCndashH in the ndashCH=CHndash group of14-unit

836955 840812 848849(flat top) blue shift of peak


3000 2500 2000 1500 1000 500

(A)(B)

(C)

(D)

(E)

(F)

(G)

Wavenumbers (cmminus1)

Figure 3 FTIR spectra of polyisoprenes of variable microstructurecontent (A) cis-14- = 100 34- = 0 12- = 0 (B) trans-14- =996 34- = 02 12- = 02 (C) 14- = 90 34- = 5 12- = 5(D) 14- = 53 34- = 24 12- = 23 (E) 14- = 30 34- = 59 12-= 11 (F) 14- = 24 34- = 63 12- = 13 (G) 14- =18 34- = 6712- = 15

800900

84178

8870990831


(a)

2740 2720 2700

2727


(b)

Figure 4 Samples of absorption values of peaks of polyisoprene

12-

PIp

A910A27274 6 8 10 12 14

468

101214161820222426

(a)

0 5 10 15 20 25 30 35 400

10

20

30

40

50

60

70

34-

PIp

A888A2727

(b)

2 4 6 8 10 12 14102030405060708090

100

14-

PIp

A840A2727

(c)

Figure 5 The absorption coefficient calculation of (a) 910 cmminus1 (b)888 cmminus1 and (c) 840 cmminus1 peaks of FTIR spectra of polyisoprene

The samples shown in Table 1 are calculated with thismethod and the results are given in Figure 5

After regression of measured points of testing pointsbased on a least-squares method the formula of microstruc-ture content is shown as follows

11988312-PIp = 221[119860] 910 cmminus1 minus 610

11988334-PIp = 192[119860]888 cmminus1 minus 340

11988314-PIp = 655[119860]840 cmminus1 + 229

(4)

Because of 910 888 and 840 cmminus1 peak overlaps partlythe errors of calculated values of integrated intensity 119860 willincrease when the peakrsquos intensity is too small Therefore the


microstructure content shall be calculated with two higherpeaks In the 12- and 34-unit the double bond is on thebranched chain and belongs to asymmetry substitute so theirdipole momentrsquos shift is bigger than that of 14-unit As aresult the integrated intensity of 910 and 888 cmminus1 peak is farstronger than 840 cmminus1 peak when the contents of their cor-responding units are the same Therefore the calculation ofmicrostructure content of polyisoprene shall choose theformer two peaks

4 Conclusion

The change of microstructure content of polyisoprene cancause a lot of differences in FTIR spectra The describedmethod by FTIR can be used to determine themicrostructurecontent of polyisoprene 910 and 888 cmminus1 peaks of 12- or34-unit have higher absorption ability than 840 cmminus1 peaksof 14-unit therefore 910 and 888 cmminus1 peaks shall be usedfirst for the quantitative analysis of microstructure content ofpolyisopreneThe quantitative calculation formulas were alsoobtained

References

[1] J E Puskas F Peruch A Deffieux et al ldquoBiomimetic carboca-tionic polymerizations III Investigation of isoprene polymer-ization initiated by dimethyl allyl bromiderdquo Journal of PolymerScience Part A vol 47 no 8 pp 2172ndash2180 2009

[2] J E Puskas C Peres F Peruch et al ldquoBiomimetic processes IVcarbocationic polymerization of isoprene initiated by dimethylallyl alcoholrdquo Journal of Polymer Science Part A vol 47 no 8pp 2181ndash2189 2009

[3] A Avgeropoulos S Paraskeva N Hadjichristidis and E LThomas ldquoSynthesis and microphase separation of linear tri-block terpolymers of polystyrene high 14-polybutadiene andhigh 34-polyisoprenerdquo Macromolecules vol 35 no 10 pp4030ndash4035 2002

[4] B Wang D Wang D Cui et al ldquoSynthesis of the first rareearth metal bis(alkyl)s bearing an indenyl functionalized N-heterocyclic carbenerdquoOrganometallics vol 26 no 13 pp 3167ndash3172 2007

[5] G Ricci M Battistella and L Porri ldquoChemoselectivity andstereospecificity of chromium(II) catalysts for 13-diene poly-merizationrdquo Macromolecules vol 34 no 17 pp 5766ndash57692001

[6] G Ricci DMorganti A Sommazzi R Santi and FMasi ldquoPoly-merization of 13-dienes with iron complexes based catalystsinfluence of the ligand on catalyst activity and stereospecificityrdquoJournal of Molecular Catalysis A vol 204-205 pp 287ndash2932003

[7] C Bazzini A Giarrusso L Porri B Pirozzi and R Napoli-tano ldquoSynthesis and characterization of syndiotactic 34-polyisoprene prepared with diethylbis(221015840-bipyridine)iron-MAOrdquo Polymer vol 45 no 9 pp 2871ndash2875 2004

[8] T Yu B Huang W Yao et al ldquoResearch and development of34-polyisoprene rubberrdquo China Synthetic Rubber Industry vol27 no 2 pp 122ndash126 2004

[9] W Zhang B Huang A Du et al ldquoProperties of TPIHVBRNRblendsrdquo China Rubber Industry vol 49 no 1 pp 5ndash8 2002

[10] W Zhang B Huang A Du et al ldquoProperties of TPIHVBRSBR blendsrdquo China Rubber Industry vol 49 no 2 pp 69ndash722002

[11] Z Zhao ldquoThe applied technology and properties of polyiso-prene of high 34-isomer contentrdquo China Rubber Collection ofTranslations no 2 pp 66ndash69 1996

[12] B Huang W Zhang A Du et al ldquoApplication of TPIHVBRblend to treadrdquo China Rubber Industry vol 49 no 3 pp 133ndash137 2002

[13] D Derouet S Forgeard J-C Brosse J Emery and J-Y BuzareldquoApplication of solid-state NMR (13C and29Si CPMAS NMR)spectroscopy to the characterization of alkenyltrialkoxysilaneand trialkoxysilyl-terminated polyisoprene grafting onto silicamicroparticlesrdquo Journal of Polymer Science Part A vol 36 no 3pp 437ndash453 1998

[14] V Arjunan S Subramanian and S Mohan ldquoFourier transforminfrared andRaman spectral analysis of trans-14-polyisoprenerdquoSpectrochimica Acta Part A vol 57 no 13 pp 2547ndash2554 2001

[15] B Huang J He J Song et al ldquoNew polymerization methodof high trans1 4mdashpolyisoprenerdquo CN1048257C China January2000

[16] B Huang Z ZhaoW Yao et al ldquoIndustrial productionmethodof high trans14mdashpolyisoprenerdquo CN1847272A China October2006

[17] P Wang H Shao W Yao et al ldquoPolymerization of isopreneinitiated with tetra-n-butyl titanate supported titanium catalystand triethylaluminiumrdquo China Synthetic Rubber Industry vol32 pp 284ndash284 2009

[18] R Gao T Yu L Bi et al ldquoResearch on novel Mg-Ti-Al complexand its catalysis for olefin polymerizationrdquo China SyntheticResin and Plastics vol 24 no 6 pp 25ndash28 2007

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Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


2 Experimental

21 Materials All the polyisoprene samples with variablemicrostructure content were polymerized according to [15ndash18]

22 Characterization

221 FTIR Tensor 27 (Bruker German) has been used in theanalysis The samples are tested by ATR-FTIR with 4 cmminus1resolution and scanned 32 times

222 1H NMR AV500 (Bruker German) has been used inthe analysis 1H NMR spectra of the polyisoprene in CDCl

3

were obtained at 50013Hz and chemical shifts were referredto TMS

The 1H NMR spectrum of polyisoprene which contains14- 12- and 34-unit is shown in Figure 112057552sim5012057550sim48and 12057548sim46 peaks are ascribed to the olefinic hydrogen of14- 12- and 34-unit respectively Determining the intensityof these spectral lines then calculating 14- 12- and 34-unitcontent with formula (1) and the results are shown in Table 1

11988314-PIp

=int 12057552ndash50


11988312-PIp

=int 12057550ndash482


11988334-PIp

=int 12057548ndash462


(1)

3 Results and Discussion

31 Analysis of FTIR Spectra of Polyisoprene Polyisoprenehas four kinds of microstructure which are cis-1 4- trans-14- 1 2- and 3 4-polyisoprene as shown in Figure 2

Figure 3 shows seven FTIR spectra of polyisoprene withdifferent microstructure content

The characterization and attribution peaks of FTIR spec-tra of polyisoprene are listed in Table 2

It can be seen from Figure 3 and Table 2 that the differ-ence of FTIR behavior of the polyisoprene microstructuresis obvious However only 910 888 and 840 cmminus1 peakscan be used for quantitative calculation of microstructurecontent of polyisoprene It is because that the peaks forquantitatively calculation must have moderate intensity littleinterfering factors by other peaks or conditions and so onExcept for those differences shown in Table 2 Table 3 showssome frequency excursion caused by microstructure contentchanging

0

50

100

150

20051345121

4966494649004875484247394670

056

057

026

100

t1 (ppm)450500550

Figure 1 1H NMR spectrum of polyisoprene

Table 1 Microstructure contents of polyisoprene by 1H NMR

Sample 14-mol 34-mol 12-molA 100 (cis-14) 0 0B 996 (trans-14) 02 02C 90 5 5D 53 24 23E 30 59 11F 24 63 13G 18 67 15

32 Quantization Calculation of Microstructure Content ofPolyisoprene by FTIR According to the Beer-Lambert lawthe integrated intensity 119860 of a characteristic band can beexpressed as follows

119860 = 119887119888int

+infin

0

120576 (]) 119889] (2)

Here 120576 is the absorption coefficient 119887 is the thickness 119888is the concentration and ] is the wavenumber

Choosing a peak which has moderate intensity and is notaffected by configuration conformation or other structurefactors as internal standard of thickness then formula (2) canbe changed to the following

[119860] =1198601

1198600

= 1198881[

[

int+infin

0120576 (1205991) 119889120599

1198880int+infin

0120576 (1205990) 119889120599

]

]

= 1198881sdot 119896 (3)

Here ldquo1rdquo means characteristic band and ldquo0rdquo meansinternal standard band ldquo119870rdquo is the correction factor and canbe calculated by 1HNMRdates As described above 910 888and 840 cmminus1 peaks can be used for quantitatively calculatingmicrostructure content of polyisoprene Table 2 shows thatthere is seldom peak which can meet the request of internalstandard peak In this paper 2727 cmminus1 is used as internalstandard peak The integrated intensity 119860 are calculated bythe software of FTIR and the integration methods are shownin Figure 4


CC C C

HC C

H

CH2 CH2

CH2CH2

CH3

CH2

CH3

CH2

CH2

n

n

n n

H2C

H3C

H3CCH

CH

12- 34- cis-14- trans-14-












34-unit



(12-unit)






of trans-14-unit



of cis-14-unit












889023 888059 887095 Red shift of peak




3000 2500 2000 1500 1000 500

(A)(B)

(C)

(D)

(E)

(F)

(G)



800900

84178

8870990831


(a)

2740 2720 2700

2727


(b)


12-

PIp

A910A27274 6 8 10 12 14

468

101214161820222426

(a)

0 5 10 15 20 25 30 35 400

10

20

30

40

50

60

70

34-

PIp

A888A2727

(b)

2 4 6 8 10 12 14102030405060708090

100

14-

PIp

A840A2727

(c)






11988314-PIp = 655[119860]840 cmminus1 + 229

(4)




4 Conclusion


References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




CC C C

HC C

H

CH2 CH2

CH2CH2

CH3

CH2

CH3

CH2

CH2

n

n

n n

H2C

H3C

H3CCH

CH

12- 34- cis-14- trans-14-












34-unit



(12-unit)






of trans-14-unit



of cis-14-unit












889023 888059 887095 Red shift of peak




3000 2500 2000 1500 1000 500

(A)(B)

(C)

(D)

(E)

(F)

(G)



800900

84178

8870990831


(a)

2740 2720 2700

2727


(b)


12-

PIp

A910A27274 6 8 10 12 14

468

101214161820222426

(a)

0 5 10 15 20 25 30 35 400

10

20

30

40

50

60

70

34-

PIp

A888A2727

(b)

2 4 6 8 10 12 14102030405060708090

100

14-

PIp

A840A2727

(c)






11988314-PIp = 655[119860]840 cmminus1 + 229

(4)




4 Conclusion


References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




3000 2500 2000 1500 1000 500

(A)(B)

(C)

(D)

(E)

(F)

(G)



800900

84178

8870990831


(a)

2740 2720 2700

2727


(b)


12-

PIp

A910A27274 6 8 10 12 14

468

101214161820222426

(a)

0 5 10 15 20 25 30 35 400

10

20

30

40

50

60

70

34-

PIp

A888A2727

(b)

2 4 6 8 10 12 14102030405060708090

100

14-

PIp

A840A2727

(c)






11988314-PIp = 655[119860]840 cmminus1 + 229

(4)




4 Conclusion


References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





4 Conclusion


References


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article fourier transform infrared spectral

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