Recent developments in the synthesis, thermostability and liquid crystal properties of aromatic polyamides

Abstract

Wholly aromatic polyamides were developed and commercialised some decades ago, and since then a great deal of effort has been expended to try to improve in particular the processability of the early materials. Work has focussed on attempting to improve polymer solubility in organic solvents, and to reduce the melting point of materials, by synthesizing a variety of macromolecular backbones with many different types of substituents. The challenge has been to modify these polymers, while not causing adverse changes in the unique and useful physical properties of this group of polymers. This has led to the development of entirely novel synthetic strategies to allow, for example, the introduction of potentially reactive groups, and also to an interest in the potential lyotropic and thermotropic liquid crystalline properties of these polymers. This review describes the various synthetic methodologies which have emerged in recent years, and then summarises and categorises progress in the understanding of the structure-property relationships of the polymers produced. Properties such as solubility, thermostability, lytropism and thermotropism are highlighted.