what is polymer? - İtÜweb.itu.edu.tr/okayo/smart1.pdf · a polymer is a large molecule consisting...
TRANSCRIPT
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?
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?
• 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)
• 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)
• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
• Polyurethane
• PET and other polyesters
• Polyamides
• Silicones
• Polycarbonates
Polymers of Step Polymerization:
Addition (Chain) polymerization
(initiated by radicals):
4) CHAIN TRANSFER
3) TERMINATION
2) PROPAGATION
1) INITIATION
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
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
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
I = initiator = monomer dropletA = primary radical
I
I
II
WATER
WATER
A
A
EMULSION POLYMERIZATION:
WATER
WATER
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
Cellulose Starch
Already existing polymers in nature BIOPOLYMERS
Polysaccharides (cyclolinear polyethers)
Chitin (N-acetyl group instead of OH)
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
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.
Hydrophobic blockHydrophilic block
b-sheet structure
Silk fibroin
Generating 3D porous silk fibroin
Scaffold for tissue engineering
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.
Structures• Linear
• Branched
• Crosslinked
•Thermoplast
•Thermoset
•Homopolymer
•Copolymer (alternating, block, random,
graft) radical reactivity ratios !
•Terpolymer
Crystalline domains ~ strong, brittle
Amorphous domains ~ tough
crystalline amorphous
crystalline amorphous
1) Effect of polymer structure
Polymers with a high degree of crystallinity
Polypropylene
Syndiotactic polystyrene
Nylon
Aramids (Kevlar, Nomex)
Polyketones
Mainly amorphous polymers
Polymethylmethacrylate
atactic polystyrene
Polycarbonate
Polyisoprene
Polybutadiene
Tg ~ backbone stiffness
-1270C>> 5000C 1900C
100% crystalline 100 % amorphous
THERMAL BEHAVIOR ( Tm ve Tg)
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
Hatched area = stress * strain = force * deformasyon = energy
Energy required to break a sample = toughness
Toughness
Force required to break a sample = strength
To break a polymer sample, it needs:
Large force, but low energy
(brittle)Lesser force but larger energy
Small force and small energy
PS
PMMA
PCO3
PVC
PE
PP
PVC + plast.
Kevlar
Karbon fiber
Naylon
Polyisoprene
Polybutadiene
Polyisobutylene
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
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
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:
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
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
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
/ (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
“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
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
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)
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
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
+1) via condensation polymerization
Triol diisocyanate
2) via addition polymerization
(VINYL – DIVINYL MONOMER COPOLYMERİZATION)
+
Monovinyl monomer Divinyl monomer
From monomers:
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
.
.
. + . .
.
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
(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
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