Thermotropic Liquid Crystal Aromatic Copolyesters Containing Cycloaliphatic Units

Abstract

Thermotropic liquid crystal behaviour of polymeric systems has been intensively investigated in recent years. Aromatic polyesters having main chain mesogenic units are among the most promising materials; however, it is recognized that it is necessary to disrupt the perfect regularity of simple para-linked aromatic polymers in order to lower the melting ranges to manageable levels. Various polyester systems have been synthesized by Blumstein,¹ Jackson,² Lenz³ as shown also in previous publications by these authors and by others. The various approaches, as summarized by Griffin and Cox,⁴ to disrupt the chain packing have been investigated. The most common modification is to incorporate flexible links consisting of short aliphatic chains. With increasing length of these spacers the overall chain cohesion in the melt is lowered, resulting in a corresponding lower melting point often with distinct odd-even effects related to the number of methylene groups in the spacer.

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