Chapter 4. Polymer Structure

1. Polymer ?

2 M l l W i ht2. Molecular Weight

3. Molecular Structure

4 Crystallinity4. Crystallinity

Natural Polymers : Wood, rubber, cotton, wool, leather

proteins, enzymes, starches

Synthetic Polymers : plastics, rubber, fiber

Saturated hydrocarbon: C

H

C

H

HH

H H

Unsaturated hydrocarbon:

H H

C

H

H

C

H

H

C C HH

Isomerism

H H H H

C C CH C H

HHHH

normal butane

H

C C CH H

H HC HH

isobutane

HHH

The chemistry of polymer molecules

C

H

C

H

monomer

H H

Initiator or catalyst species

C

H

H

C

H

H

R* + C C*R

H H

HH

H H H HH H H H

H H HH

C C CR C*

HHHH

C C*R

HH

C

H

C

H

+

M l l W i htMolecular Weight

The number average molecular weight : ∑= iin MxMg g

The weight average molecular weight :

∑ iin

∑= iiw MwM

mMn n

n = mMn w

w =The degree of polymerization :

∑ f∑= jjmfm for copolymer

Ex 4.1 ) p103, PVC

a)

b) The atomic weight of C, H, and Cl = 12.01, 1.01, 35.45 g/mol

m ===

==Mn n

n mn

Molecular Shape

• freely-jointed modely j

The probability distribution of r -> the root mean square end-to-end distance = <r2>1/2

<r2>1/2 =n1/2l {n: # of chain, l: length}

Molecular Structure

Molecular Configuration

Stereoisomerism

1. isotatic configuration

C C C C

H H H H

C C C C

H H H H

2. syndiotatic configuration

HRHR HRHR

C C C C

H H R H

C C C C

H H R H

i fi i

C C C C

HHHR

C C C C

HHHR

H H H H H H R H3. atatic configuration

C C C C

H H H H

HRHR

C C C C

H H R H

HHHR

Geometrical isomerism

1. Trans structureC C

H2C

H

H3C

CH2

2. Cis structureC C

HH3C

C C

H2CCH2

Copolymer

Synthetic rubberSynthetic rubber

Styrene-Butadiene rubber (SBR)

Nitrile rubber (NBR)

Thermoplastic polymer

Recycle, remoldingy , g

Ex) PE, PP, PS, PMMA, PVC

Thermosetting polymer

Just one time useJust one time use

Ex) rubber, epoxy, phenolic resins

Polymer Crystal

100)()(% ×

−−

=acs

ascitycrystallinρρρρρρ

Polymer Crystal

Semicrystalline polymer

Fringered-micelle model

h liSpherulite

Homework (due date : 3/24)Homework (due date : 3/24)

Ch t 3 #3 41 #3 53 #3 56 #3 68 #3 71 #3 75 #3 78 #3 91Chapter 3. #3.41 #3.53 #3.56 #3.68 #3.71 #3.75 #3.78 #3.91

Chapter 4. #4.5 #4.10 #4.14 #4.19 #4.23 #4.26