Segmented block copolymers based on polyamide-4,6 and poly(propylene oxide)

Segmented copolymers were obtained through copolymerization of polyamide-4,6 and poly(propylene oxide) (PPOx). An amine-terminated PPOx (‘soft’) segment of molar mass 430 was reacted with nylon-4,6 salt in an autoclave (30 min, 210°C, 7 bar). In this reaction a prepolymer was prepared, which was postcondensed afterwards. In ethanol, a considerable amount of material could be extracted from the solid copolymers of low polyamide content. Extractability was found to be strongly reduced with increasing polyamide content, i.e. increasing length of the polyamide (‘hard’, crystallizable) segments. Torsional tests showed an extended rubber plateau of fairly constant modulus. Whereas PPOx has a Tg of −60°C, the Tg values of the copolymers were higher as a result of (i) the restricted length of the PPOx segments and (ii) dissolution of uncrystallized polyamide segments in the PPOx phase. The high melting point of polyamide-4,6 was approached by the copolymer of high polyamide content, but the softer copolymers had lower melting points because of insufficient length of the polyamide segments.