HETEROMERIC LIQUID-CRYSTALLINE ASSOCIATION CHAIN POLYMERS - STRUCTUREAND PROPERTIES

Liquid-crystalline association chain polymers involving hydrogen-bond connectivities between pyridyls and carboxylic acids have been synthes ized and characterized by optical, thermal, infra-red, solid-state nuc lear magnetic resonance and rheological analysis. For one system a che mical reaction occurs during its preparation, which alters its primary (covalent) structure. The liquid-crystalline thermal stability is inc reased by this modification, wherein it has greatly diminished crystal linity. Variable-temperature infra-red spectroscopy was used to follow the extent of hydrogen bonding as a function of temperature. At the m elting 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 thr ough the mesophase, as would be expected for increased hydrogen bondin g at lower temperatures.