LAYER STRUCTURE .1. POLY(PHENYLENE TEREPHTHALAMIDE)S DERIVED FROM MONOKIS(ALKYLTHIO)TEREPHTHALIC, DIKIS(ALKYLTHIO)TEREPHTHALIC, AND TETRAKIS(ALKYLTHIO)TEREPHTHALIC ACIDS

Tetrakis(alkylthio)terephthalic acids were prepared by nucleophilic substitution of diethyl tetrachloroterephthalates. Three groups of substituted poly(phenylene-terephthalamide)s were prepared polycondensation of N,N'-bis(trimethylsilyl)-1,4-diaminobenzene with substituted terephthaloyl chlorides. Mono-, bis-, and tetrakis(alkylthio)terephthaloyl chlorides with octyl or hexadecyl side chains were used as reaction partners. These polyaramides form three different kinds of layer structures with H-bonded sheets of the main chains and partially ordered paraffin domains between these sheets. The reversible melting and crystallization of the paraffin domains can be monitored by C-13 NMR CP/MAS and DSC measurements. All polyaramides are infusible below 400-degrees-C. Their solubilities were determined in 17 solvents. Extremely poor solubilities were found in all cases. It is discussed and demonstrated that polar aromatic side chains play the role of a ''bound solvent'' more efficiently than alkyl side chains.