Heterogeneous polycondensation for composition control of poly(p-mercaptobenzoyl-co-p-benzamide) by shearing

Composition control of aromatic poly(thioester-amide) was examined by the reaction-induced phase separation during polymerization of S-acetyl-4- mercaptobenzoic acid (AMBA) and p-acetylaminobenzoic acid (AABA) in aromatic solvent. The poly(thioester-amide)s were obtained as precipitates and their yields became lower at the middle range of the content of AMBA in feed (χ_f). The contents of p-mercaptobenzoyl (MB) moiety (χ_p) in the precipitates prepared without shearing were in good agreement with the χ_f values. In contrast to this, the χ_p values of the precipitates prepared at χ_f of 50-70 mol % under shearing were much lower than the χ_f values. The reaction rate of AMBA increased with shearing, whereas that of AABA was unchanged by shearing. This shearing effect on the reaction rates accelerated to form the homo-oligomers. The solubility of MB oligomers enhanced by shearing, whereas that of p-benzamide oligomers did not enhance owing to the strong interaction through hydrogen bonding. The MB oligomers were inhibited to be precipitated, resulting in the lower χ_p values than the χ_f values. The composition could be controlled by the application of the shearing to the heterogeneous polymerization.