Investigations on the role of acyl initiators and CO2 in nylon 4 polymerization

Abstract

The preparation of high molecular weight nylon 4 with alkali metal pyrrolidonate catalysts, acyl initiators, and CO2 was studied. Isolated sodium pyrrolidonate and the appropriate amount of acyl initiator gave unusually high molecular weight nylon 4 (mw >200,000). The molecular weight-initiator concentration relationship indicates that acyl compounds play a dual role in the polymerization, acting both as initiators and scavengers for chain-terminating impurities. One potential chain terminator was identified as 4-aminobutyric acid. The high polymer molecular weights obtained in the presence of CO2 can also be explained by the scavenging of chain terminators by CO2. Determination of the number of growing chains, however, shows that CO2, unlike the acyl compounds, is not an initiator in nylon 4 polymerization.