New Insights in the Synthesis of High-Molecular-Weight Aromatic Polyamides-Improved Synthesis of Rod-like PPTA

By employing a variation of the polyamidation method using in situ silylated diamines and acid chlorides, it was possible to obtain a rod-type polyamide: poly(p-phenylene terephthalamide) (PPTA, a polymer used in the high-value-added material Kevlar), with a molecular weight much higher than that obtained with the classical and industrial polyamidation method. The optimization of the method has consisted of using, together with the silylating agent, a mixture of pyridine and a high-pKa tertiary amine. The research was complemented by a combination of nuclear magnetic resonance and molecular simulation studies, which determined that the improvements in molecular weight derive mainly from the formation of silylamide groups in the growing polymer.

Automated summary

By modifying the polyamidation method and using in situ silylated diamines and acid chlorides, a rod-type polyamide, poly(p-phenylene terephthalamide) (PPTA), with a significantly higher molecular weight than the classical and industrial method was obtained. The optimization of the method involved the use of a mixture of pyridine and a high-pKa tertiary amine along with the silylating agent. Nuclear magnetic resonance and molecular simulation studies confirmed that the increase in molecular weight was mainly attributed to the formation of silylamide groups in the polymer chain.