Synthesis and Characterization of Novel Water-Soluble Polyamides with Enhanced Gas Barrier Properties

Abstract

Poly(hexamethylene isophthalamide) (PA6I), an amorphous polymer characterized by high temperature resistance and significant oxygen barrier performances, has been chemically modified by using the 5-sulfoisophthalic acid sodium salt as a comonomer. Then, ionic groups have been randomly distributed along the polymeric chains. The new sulfonated PA6I samples were studied in order to understand structure–property relationships. It results that ionomeric PA6Is present an increment of Tg and, accordingly, a decrement of the oxygen transmission rate at 50% of relative humidity with the increment of the ionic content. Ionic groups, indeed, induce the formation of new interactions among the polymer chains, and then, a complex macromolecular network is realized. Interestingly, a molar amount of ionic groups equal to or higher than 10% makes sulfonated polyamides water-soluble. This characteristic, exploited to prepare new coatings on different polymers, opens a range of new applications for ionomeric PA6I.