Carboxylic Elastomers

Abstract

Abstract The degree to which a polymer is rubbery is influenced by the detailed shape and chemical composition of the macromolecules. Polymers which are rubbery possess relatively weak interchain forces and may lack linear symmetry and orderly arrangement of the molecule. As stronger interchain forces are added and symmetry and regularity are increased, the rubbery characteristics are gradually supplanted by those of fiber forming materials. Copolymerization with hydrocarbon chains may be used to reduce polymer to polymer interaction, destroy regularity and symmetry and favor rubbery characteristics. On the other hand it may be employed to introduce polar groups into hydrocarbon polymers and thereby increase interchain and intrachain forces. With increasing amounts of these polar groups polymer strength increases at the expense of elasticity with respect to both speed and range of extension and recovery. The polar groups also alter the solvent resistance of the polymer. In copolymerizations, carboxylic monomers tend to destroy regularity and symmetry thereby favoring rubbery properties over crystallinity. The strong polar nature of the carboxyl groups however increases interchain and intrachain forces imparting increased strength to the polymer at the expense of elasticity. Carboxyl groups were first introduced into rubbers for the purpose of altering polymer properties. When carboxyl groups are so employed, the resultant carboxylic rubbers are best regarded as polar elastomers. Carboxyl groups have also been introduced into rubbers in order that reactions characteristic of the carboxylic functional group might be employed to crosslink the polymer chains or attach them to other molecules or surfaces. When the carboxyl group is present in order that its functional reactivities may be employed, the carboxylic rubbers are best regarded as functional elastomers. This review is concerned with the preparation, properties and evaluation of carboxylic rubbers both as polar and as functional elastomers.