what is polymer? · mechanical properties of porous polymeric scaffolds and cortical bone materials...
TRANSCRIPT
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A polymer is a large molecule consisting of repeating units joined by
(covalently) bonds.
Poly = many
mer = parts
In organic chemistry we talk about homologous series that runs
methane, ethane, propane, ..... In this series two methyl groups
(CH3) are joined by methylene (-CH2-) bridges. As you extend this
series you create polyethylene:
CH3 - CH2 - CH2 - ... - CH2 - CH2 - CH3
or shortly CH3 [ - CH2 - ]n - CH3 or [ - CH2 - ] n
What is Polymer?
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Chain conformation~ bond length
~ valence angle
~ angle of rotation
Random coilPlanar zig-zag
r
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Flowchart of Polymeric Materials
• InorganicNatural: Clays (Bricks, cement, pottery)
Sands (Glass)
Synthetic: Silicones, polysulfides
• OrganicNatural: Polysaccharites, Proteins, DNA, Polyisoprene Rubbers
Synthetic: Adhesives, Fibers, Coatings, Plastics, Rubbers
Polymer Classification
Addition (chain) vs. Condensation (step)
Did you break a double bond to make your polymer or did you eliminate a by-product such as water, methanol, HCl ?
What about epoxies and polyurethanes?
How the molecular weight changes with the reaction time?
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• polyethylene
• polystyrene
• poly(vinyl chloride)
• poly(vinyl acetate)
• poly(methyl methacrylate)
• polypropylene
• poly(tetrafloroethylene) [ teflon]
• poly(isoprene)
• poly(acrylonitril)
Polymers of Addition (Chain) Polymerization:
(classical materials – not smart)
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• polyethylene
• polystyrene
• poly(vinyl chloride)
• poly(vinyl acetate)
• poly(methyl methacrylate)
• polypropylene
• poly(tetrafloroethylene) [ teflon]
• poly(isoprene)
• poly(acrylonitril)
Polymers of Addition (Chain) Polymerization:
(classical materials – not smart)
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• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
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• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
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• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
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• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
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• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
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• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
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Addition (Chain) polymerization
(initiated by radicals):
4) CHAIN TRANSFER
3) TERMINATION
2) PROPAGATION
1) INITIATION
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1) INITIATION
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2) PROPAGATION
t
tc
t
p
nk
k
Rk
MkX 1
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3) TERMINATION (BY COUPLING)
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3) TERMINATION (BY DISPROPORTIONATION)
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4) CHAIN TRANSFER
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Addition (Chain) polymerization (ionic):
ANIONİC:
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Addition (Chain) polymerization (ionic):
ANIONIC:
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Addition (Chain) polymerization (ionic):
CATIONIC:
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METHODS FOR THE PREPARATION OF ADDITION
POLYMERS:
SUSPENSION: + heat control
+ separation
Bulk (or solution) polymerization
in droplets (10 – 1000 mm)
SOLUTION: Monomer +solvent + initiator
Styrene – toluene / acrylonitril -
chloroform
+ heat control
- solvent
EMULSION: Polymerization in micelles + heat control
- emulsifier
BULK: Monomer + initiator - heat control
Precipitation polymerization
Cryopolymerization
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Principle: Sea ice is less salty than sea water. Brine rejection from freezing aqueous salt solutions
Cryopolymerization: Polymerization conducted in apparently frozen solutions
Lozinsky VI. Russ Chem Rev 2002;71:489
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Growing
solvent crystals
Unfrozen
liquid channels
containing
monomers
Principle: Sea ice is less salty than sea water. Brine rejection from freezing aqueous salt solutions
Monomer solution
Cryopolymerization: Polymerization conducted in apparently frozen solutions
at subzero temperatures
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cont. phase
monomer + initiator
filtration
SUSPENSION POLYMERIZATION:
PIB
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emulsifier
micelle
Organic
monomer
Monomer solubilized
in a micelle
+
EMULSION POLYMERIZATION:
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I = initiator = monomer dropletA = primary radical
I
I
II
WATER
WATER
A
A
EMULSION POLYMERIZATION:
WATER
WATER
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Hydrophilic monomerHydrophobic comonomer
Surfactant
Hill, A.; Candau, F.; Selb, J. Macromolecules 1993, 26, 4521.
Regalado, E.J.; Selb, J.; Candau, F. Macromolecules 1999, 32, 8580.,
MICELLAR POLYMERIZATION:
Initiator
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Prepared by OKAY
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Length of hydrophobic block =
Supramolecular network
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Cellulose Starch
Already existing polymers in nature BIOPOLYMERS
Polysaccharides (cyclolinear polyethers)
Chitin (N-acetyl group instead of OH)
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Protein
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Aminoacides
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Queen of Fibre since 3000 BC.
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Silkworm cocoons Cocoon silk
Vepari, C.; Kaplan, D. L. Prog. Polym. Sci. 2007, 32, 991.
Vollrath, F.; Porter, D. Polymer 2009, 50, 5623.
Hardy, J. G.; Romer, L. M.; Scheibel, T. R. Polymer 2008, 49, 4309.
Zhou, C. Z.; Confalonieri, F.; Medina, N.; Zivanovic, Y.; Esnault, C.; Yang, T.; Jacquet, M.; Janin, J.;
Duguet, M.; Perasso, R.; Li., Z. G. Nucleic Acids Res. 2000, 28, 2413.
Sofia, S.; McCarthy, M. B.; Gronowicz, G.; Kaplan, D. L. J. Biomed. Mater. Res. 2001, 54, 139.
Jin, H. J.; Fridrikh, S. V.; Rutledge, G. C.; Kaplan, D. L. Biomacromolecules 2002, 3, 1233.
Jin, H. J.; Kaplan, D. L. Nature 2003, 424, 1057.
Kim, U. J.; Park, J.; Li, C.; Jin, H. J.; Valluzzi, R.; Kaplan, D. L. Biomacromolecules 2004, 5, 786
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b-sheet
b-sheet
b-sheet
Silk fibroin
(Gly-Ala-Gly-Ala-Gly-Ser)6 amino acid repead units
self-assemble into anti-parallel b-sheet structure
Jin, H. J.; Kaplan, D. L. Nature 2003, 424, 1057.
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Hydrophobic blockHydrophilic block
b-sheet structure
Silk fibroin
Generating 3D porous silk fibroin
Scaffold for tissue engineering
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Mechanical properties of porous polymeric scaffolds and cortical bone
Materials Compressive
strength (kPa)
Compression
modulus (kPa)
Ref.
Cortical bone ~ 200 000 ~ 20 x 106
(~ 20 GPa)
1
Collagen ~15 ~150 2
Chitosan ~45 ~750 2
Silk ~300 up to ~ 3 x 103
(~ 3 MPa)
3
1. Yaszemski et al. Biomaterials 17, 175, 1996
2. Kim et al. Fibers Polym 2, 64, 2001
3. Kaplan group, Biomaterials 26, 2775, 2005.
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(
(
O
O
CH2
O
P O-O
Base
Polynucleotides or nucleic acids
Deoxyribonucleic acid (DNA)
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ds-DNA
ss-DNA
HeatingSlow cooling
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Structures• Linear
• Branched
• Crosslinked
•Thermoplast
•Thermoset
•Homopolymer
•Copolymer (alternating, block, random,
graft) radical reactivity ratios !
•Terpolymer
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Fine Structure:
•Atactic,
•Isotactic
•Syndiotactic
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Crystal and amorph structures
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Crystalline domains ~ strong, brittle
Amorphous domains ~ tough
crystalline amorphous
crystalline amorphous
1) Effect of polymer structure
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2) Effect of intermolecular interactions
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Polymers with a high degree of crystallinity
Polypropylene
Syndiotactic polystyrene
Nylon
Aramids (Kevlar, Nomex)
Polyketones
Mainly amorphous polymers
Polymethylmethacrylate
atactic polystyrene
Polycarbonate
Polyisoprene
Polybutadiene
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Tg ~ backbone stiffness
-1270C>> 5000C 1900C
100% crystalline 100 % amorphous
THERMAL BEHAVIOR ( Tm ve Tg)
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THERMAL BEHAVIOR ( Tm ve Tg)
Tg ~ side groups
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Strength (tensile, compressional): Stress required to fracture a
polymer sample)
Elastic or Young’s modulus: resistance against the deformation
soft plastics
MECHANICAL PROPERTIES:
Stress-strain curves
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Hatched area = stress * strain = force * deformasyon = energy
Energy required to break a sample = toughness
Toughness
Force required to break a sample = strength
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To break a polymer sample, it needs:
Large force, but low energy
(brittle)Lesser force but larger energy
Small force and small energy
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PS
PMMA
PCO3
PVC
PE
PP
PVC + plast.
Kevlar
Karbon fiber
Naylon
Polyisoprene
Polybutadiene
Polyisobutylene
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Molecular Weight of Polymers• Chain-growth (addition)
Polymerization• Step-growth (condensation)
Polymerization
MOLEKÜL AÐIRLIK
DA
ÐIL
IM
p = 0.90
p = 0.95
p = 0.98p = 0.99
MOLEKÜL AÐIRLIK
DA
ÐIL
IM
p = 0p = 0.5
p = 0.75
p = 0.9
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Average Molecular Weights
1. Mn
2. Mv
3. Mw
4. Mz
• Osmometry,
• End-group analysis,
• Colligative properties
•Light scattering,
•Small-angle neutron scattering,
•Sedimentation rates
•Sedimentation equilibrium
Ni = Number of chains having the molecular weight Mi
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pX n
1
1
p
pX w
1
1pPDI 1
t
tc
t
p
nk
k
Rk
MkX 1
t
tc
t
p
wk
k
Rk
MkX 2
For condensation polymers:
For addition polymers:
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SOLUBILITIES:
Good solvents = polymer coil dimensions (~viscosities) increase
Poor (bad) solvents = coil dimensions decrease
(Mark-Houwink)
a = 0 (hard sphere), 2 (rod), 1 (half-coil), 0.5
(theta solvent), 0.8 (good solvent)
Molecular weight ~ viscosity ~coil dimensions
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Cohesive energy density
Hildebrand solubility parameters =
(Energy required to vaporize unit volume of a
solvent) 1/2
Polystrene - toluene CH CH2
CH3
CH2 CH
C=O
NH 2
H
O
H
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N-hexane 7.3
Benzene 9.2
Acetone 10.0
Etanol 12.7
Methanol 14.5
Water 23.4
Polyethylene 7.9
Polystyrene 9.1
PMMA 9.1
Nylon 66 13.6
PAN 15.4
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/ (MPa)0.5
14 16 18 20 22 24 26 28 30
D / DCH
0.4
0.6
0.8
1.0
MOHEtOH
Ace
MEK
Ben
Tol
Xyl
Car
CH
Hep
MCH
Hex
Pen
CH2 C
CH3
CH3
Butyl rubber (polyisobutylene-co-polyisoprene), solubility parameter
determination
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DISSOLUTION OR MIXING
21 vvNkTH M 221
Flory-Huggins parameter
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“Random walk” or “random flight” approach to polymer chain
dimensions: end-to-end distance of an ideal chain
Real chains are smart
Entropy of a chain
Chains are similar to metal springs
Visualization of changes in chain dimensions: crosslinked
polymers (elastomers) and gels: Entropy of deformation, work
and modulus, swelling
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CROSSLINKED POLYMERS:
“crosslinked polymers, polymer networks, rubbers, elastomers,
rubberlike materials, polymer gels”
High deformation
Reversible deformation
Molecular characteristics: Required conditions:
Long, mobile, flexible chains,
Crosslinks between the chains
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r0 r
r
r0
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Rubbery polymers at room temperature:
Natural rubber (Tg = -730C , Tm = 280C) Styrene-butadiene copolymer
(~x)
Butyl rubber (Tg = -730C , Tm = 50C) Etylene – propylene copolymer
PDMS (Tg = -1270C , Tm = -400C) Poly(ethylacrylate)
Glassy polymers at room temperature :
Polyethylene ( CH2-CH2, crystalline) Polystyrene (CH2-CH2-Ph)
Polyacrylamide (CH2-CH-CO-NH2) PVC (CH2-CH-Cl)
Elastine (CO-NH-CH(R))
Poly(p-phenylene) (-Ph-, stiff chains)
Bakelite (Phenol-formaldehyde resin) (short chains)
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PREPARATION
1) Physical methods:
H-bonds,
complex formation
2) Chemical methods:
Starting from linear polymers (S, peroxides, radiation,...)
Starting from monomers
C
NHO
H
O
H
NH
O
C
borik asit
OH
OH
OH
OH
OH
OH
OH
OH
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1015-20 molecules
1 molecule
VULCANIZATION OF RUBBER
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S2Cl2 SCl2 + S
SCl2+ CH2 C CH CH2
CH3CH2 C
CH3
CH CH2
Cl SCl
S
CH2 C CH CH2
CH3
+
CH2 C
CH3
CH CH2
Cl
CH2 C CH CH2
Cl
CH3
(S)x
CH2 C
CH3
CH3
CH2 C
CH3
CH CH2( )n
BUTYL RUBBER
• Cold vulcanization
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+1) via condensation polymerization
Triol diisocyanate
2) via addition polymerization
(VINYL – DIVINYL MONOMER COPOLYMERİZATION)
+
Monovinyl monomer Divinyl monomer
From monomers:
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CH2
NH
COCO
NH2
CH2 CHCH2 CH +
CO
NH
CH2 CH
CH2 CHCH2 CH
CH2 CH
+
+CH2 C
CH3
CO
O
CH3
(CH2CH2OH)
C
CH3
CO
O
CH2
CH2
O
CO
CCH2
CH3
CH2
VİNYL – DIVINYL MONOMERS
• 2-Hydroxymethylmethacrylate / Ethylene glycol dimethacrylate
• Styrene / Divinylbenzene
• Acrylamide / N,N’-methylene(bis)acrylamide
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.
.
. + . .
.
1 1 2
1 2 3
1 2 3 4 n...n = 10 - 10
2 4
I 2 A
A A A
A
A
kp
kd
A
k t
(POLYACRYLAMIDE)(ACRYLAMIDE)
(POTASSIUM
PERSULFATE)
.+ ___ ++S
O
O
O O O S
O
O
OK K S
O
O
OK O2
C
H
H
C
C
H
O NH2
C
H
H
C
C
O NH2
H
( )n
LINEAR SYSTEM
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(BISACRYLAMIDE)
C
H
H
C
C
H
O N H
C
N
C
CC
HH
H
H
H
H
O
r+1 unitsr units
r + s units
s units
r units
+.
polymer chains with pendant vinyl groups
(with potential crosslink points)
.+.
.
NONLINEAR SYSTEM
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CH2 CH
C O
NH
R
monomer
CH2 CH
C O
NH
CH2
NH
C O
CHCH2
crosslinker
APS / TEMED
H2O
Created by Oguz OKAY
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Polymer Solution: Polymeric Gel:
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Non-ionic gel
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Ionic hydrogel