VARIABLE TEMPERATURE SOLID STATE PC NMR STUDIES OF SIDE GROUP CONFORMATIONS IN POLYMERS FORMING LAYERED STRUCTURES

摘要

Stiff aromatic main chain polymers have attracted considerable interest because of their possible application as high modules and high performance thermoplastics. Several concepts for lowering the n.elting temperature and increasing the solubility of the macromoleculcs have been proposed''2. One of these consists in attaching flexible aliphatic side chains to the stiff backbone. These systems have been shown to exhibit different liquid crystal mesophases depending on the length of the nonpolar flexible side chain and the layer-type packing structure. The side chains thus play a crucial role in determining the packing and the properties of these rigid rod polymers. A so-called sanidic type of chain packing yyas found to be typical lor the solid state. Longer aliphatic side chains(n=>12) lorra crystalline paraffin domains between the stacks of main chain. Chain packing of the aliplatjc substitutes and their mobility v/cre Ihe object of several studies. In the present work we discuss the results of variable temperature 13C solid state NMR measurement of poIyCphyenyiencterephthalate) derived from mono- and di-(alkylthio)terephlhalic acid, with particular emphasis on the elucidation of (lie conformations and solid state phase transition of the side chain.