WHISKERS .6. POLY(ESTER AMIDE)S DERIVED FROM 4-HYDROXYBENZOIC ACID AND 4-AMINOBENZOIC ACID

A new method for the synthesis of poly(ester-amide)s derived from 4-hydroxybenzoic acid (4-HBA) and 4-aminobenzoic acid (4-ABA) was elaborated. The silylated 4-aminobenzoic acid was acylated with 4-acetoxybenzoyl chloride under mild conditions, and the resulting dimer was polycondensed in an ''one-pot procedure'' at 350 or 400-degrees-C. In another experient, N-(4-acetoxybenzoyl)-4-aminobenzoic acid was isolated and afterwards polycondensed. Both methods gave crystalline poly(ester-amide)s of different morphology. The one-pot procedure yielded crystals looking like shavings which were characterized by elemental analyses, IR spectroscopy, wide-angle X-ray scattering, and electron microscopy. The results of these measurements suggest that the products of the one-pot procedure possess a predominantly alternating sequence, whereas the products of the two-step procedure possess a more blocky sequence. Furthermore, cocondensations with 4-acetoxybenzoic acid or its trimethylsilyl ester were conducted, and the morphology of the resulting copoly(ester-amide)s was studied. Whiskerlike crystals were only obtained from copoly(ester-amide)s containing 90 mol % 4-HBA units.