What is Polymer? · Mechanical properties of porous polymeric scaffolds and cortical bone Materials...

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?

Chain conformation~ bond length

~ valence angle

~ angle of rotation

Random coilPlanar zig-zag

r

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)

• 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

1) INITIATION

2) PROPAGATION

t

tc

t

p

nk

k

Rk

MkX 1

3) TERMINATION (BY COUPLING)

3) TERMINATION (BY DISPROPORTIONATION)

4) CHAIN TRANSFER

Addition (Chain) polymerization (ionic):

ANIONİC:


ANIONIC:


CATIONIC:

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

cont. phase

monomer + initiator

filtration

SUSPENSION POLYMERIZATION:

PIB

emulsifier

micelle

Organic

monomer

Monomer solubilized

in a micelle

+

EMULSION POLYMERIZATION:

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

Prepared by OKAY

Length of hydrophobic block =

Supramolecular network

Cellulose Starch

Already existing polymers in nature BIOPOLYMERS

Polysaccharides (cyclolinear polyethers)

Chitin (N-acetyl group instead of OH)

Protein

Aminoacides

Queen of Fibre since 3000 BC.

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.

(

(

O

O

CH2

O

P O-O

Base

Polynucleotides or nucleic acids

Deoxyribonucleic acid (DNA)

ds-DNA

ss-DNA

HeatingSlow cooling

Structures• Linear

• Branched

• Crosslinked

•Thermoplast

•Thermoset

•Homopolymer

•Copolymer (alternating, block, random,

graft) radical reactivity ratios !

•Terpolymer

Fine Structure:

•Atactic,

•Isotactic

•Syndiotactic

Crystal and amorph structures

Crystalline domains ~ strong, brittle

Amorphous domains ~ tough

crystalline amorphous

crystalline amorphous

1) Effect of polymer structure

2) Effect of intermolecular interactions

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)

THERMAL BEHAVIOR ( Tm ve Tg)

Tg ~ side groups

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

DISSOLUTION OR MIXING

21 vvNkTH M 221

Flory-Huggins parameter

“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

r0 r

r

r0

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

1015-20 molecules

1 molecule

VULCANIZATION OF RUBBER

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

Polymer Solution: Polymeric Gel:

Non-ionic gel

Ionic hydrogel

What is Polymer? · Mechanical properties of porous polymeric scaffolds and cortical bone Materials...

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