Some Industrially Important Polymers - Fundamentals of Industrial Chemistry: Pharmaceuticals, Polymers, and Business - page 117

Many of the acrylates are also made by free radical polymerization.
By varying the alcohol portion, such as methanol as in methyl acrylate or
butanol for butyl acrylate or 2-ethylhexanol as in octyl acrylate, the Tg
and other polymeric properties can be varied. As the side chain increases
in length, the T g decreases. Going from a one carbon alcohol as in methyl
acrylate to an eight carbon alcohol results in a lowering of the Tg by about
60 ∘ C. However, the cost increases. Often copolymers are made such as
in the copolymerization of methyl acrylate with butyl acrylate to optimize
properties needed for particular applications. The acrylates are commonly
used as pressure-sensitive adhesives.
If X is cyano and Y is carboalkoxy we have the cyanoacrylate polymers,
useful as adhesives. For example, ethyl cyanoacrylate is marketed as Super
Glue ® or Krazy Glue ® .

H CN H CN

CC CC

CO 2 CH 2 CH 3 CO 2 CH 2 CH 3

Ethyl cyanoacrylate

H H

m

The cyanoacrylate olefins have two electron-withdrawing groups on the
substituted carbon of the olefin and therefore can be readily polymerized in
anionic fashion by use of a base. For example, N,N-dialkyl anilines have been
used to activate the polymerization [11].

8.5 POLYESTER

An ester can be prepared by the reaction of a carboxylic acid and an alcohol
as illustrated with benzoic acid and ethanol to make ethyl benzoate. Typically,
the reaction is done with an acid catalyst, such as sulfuric acid, and the equi-
librium is shifted to the right either by removal of the water or by using a
large excess of the alcohol or both. In the reaction, an equivalent of water is
condensed or removed for each ester bond formed.

O O

OH O

+

OH + H 2 O

The reaction can also be done by a transesterification reaction. This can be
illustrated by the reaction between methyl benzoate and ethanol to form ethyl
benzoate and methanol. This too is acid catalyzed. The equilibrium can be
shifted to the right by using an excess of ethanol or by removing methanol as