1. Molecular Shape of Polymers
Polymer chains are not necessarily straight!
A single polymer chain
Bending and coiling of polymer chains

2. Molecular Configurations IsomersCl C H Cl C H
Polyvinyl chloride (PVC)
Head-to-Head Configuration
Head-to-Tail Configuration Cl C H Cl C H Cl C H Cl C H H C Cl
Syndotactic Configuration
Atactic Configuration
Isotactic Configuartion

3. Geometrical IsomerismH
CH3 H H
“cis”
Natural rubber C C C C H H
Polyisoprene H
CH3 H
Gutta percha
“trans” C C C C H H H
The change in the configuration cannot be achieved by simple rotation of the double bond!

4. Copolymers Copolymers: Having more than one type of “mer” unit. Block
Random
Alternating
Graft
Properties are improved by combining different “mers”.

5. Polymer Crysrtallinity
Usually the elastic modulus and strength increase with increasing the % of the crystalline regions.
Heating (annealing) can increase the % of the crystalline regions.
Crystalline polyethylene

6. Polyethylene Crystals
Adapted from Callister, Figures through 14-15
From dilute solution
From melt
Spherulite Structure
Chain-folded structure