Introductory Concepts and Definitions - Polymer Science and Engineering - page 35

(1-61), for example. This is what is done in the synthesis of some film-forming
polymers like alkyds (Section 7.4.2) in which crystallization is undesirable.

H
C CH 3 CH 2 OH

OH

1-61

It has been suggested that tail-to-tail linkages in vinyl polymers may constitute
weak points at which thermal degradation may be initiated more readily than in
the predominant head-to-tail structures.
Polymers of dienes (hydrocarbons containing two C—C double bonds) have
the potential for head-to-tail and head-to-head isomerism and variations in
double-bond position as well. The conjugated diene butadiene can polymerize to
produce 1,4 and 1,2 products:

HH

C C

X

H

HH

(1-16)

HC
1,2- polybutadiene

CH 2

CH 2
123 4

C C

2

The C atoms in the monomer are numbered in reaction (1-16) and the polymers
are named according to the particular atoms involved in the enchainment. There is no
3,4-polybutadiene because carbons 1 and 4 are not distinguishable in the monomer
structure. This is not the case with 2-substituted conjugated butadienes like isoprene:

CH 3
C CH 2

X

H C CH 2

1,2 − polyisoprene

H H

CH 2 CC CH 2 C

2

X

(1-17)

CH 3

CCH 3

CH 2
3,4 − polyisoprene

CH 3 H

CH 2 CC CH 2

1,4 − polyisoprene