HETEROMERIC LIQUID-CRYSTALLINE ASSOCIATION CHAIN POLYMERS - STRUCTURE AND PROPERTIES

Liquid-crystalline association chain polymers involving hydrogen-bond connectivities between pyridyls and carboxylic acids have been synthesized and characterized by optical, thermal, infra-red, solid-state nuclear magnetic resonance and rheological analysis. For one system a chemical reaction occurs during its preparation, which alters its primary (covalent) structure. The liquid-crystalline thermal stability is increased by this modification, wherein it has greatly diminished crystallinity. Variable-temperature infra-red spectroscopy was used to follow the extent of hydrogen bonding as a function of temperature. At the melting transition a discontinuous decrease in hydrogen bonding is seen. Rheological data on complexes with varying degree of polymerization show similar values of G', with gradually increasing G' on cooling through the mesophase, as would be expected for increased hydrogen bonding at lower temperatures.