SINGLE-CHAIN FLEXIBILITY AND CONFORMATION IN POLYARYLATES

This paper describes the use of molecular modeling to study the flexibility and conformation of single-chain sections of three polyarylates based on terephthalic acid and (i) bisphenol A, (ii) bisphenol based on methyl isobutyl ketone, and (iii) phenolphthalein. Configurational entropies were calculated based on the ease of rotation of various bonds. Entropies calculated for the cooperative rotation of the bisphenol phenyl rings did not correlate with the experimentally determined glass transition temperatures. However, a correlation was found using entropies determined for the independent rotation of various bonds keeping others in their minimum-energy conformation. The relative bond flexibilities can be normalized by comparing the configurational entropy in each case against that of a hypothetical freely rotating bond. These results may be useful in interpreting the gas diffusivity and thermal and mechanical properties of these polyarylates.