Low molecular weight poly(imide‐amide)s obtained by copolycondensation of 4,4′‐methylenedi(phenyl isocyanate), trimellitic anhydride and benzoic acid in N‐methyl‐2‐pyrrolidone, 3. Absolute number‐average molecular weights and glass transition temperatures

Abstract

AbstractIn depth study of low molecular weight poly(imide‐amide)s (PIA) obtained by copolycondensation of 4,4′‐methylenedi(phenyl isocyanate), trimellitic anhydride and benzoic acid by 1H and 13C NMR spectroscopy and size‐exclusion chromatography allows the determination of their absolute number‐average molecular weights M̄n, abs. Viscosimetric measurements reveal that, dissolved in N‐methyl‐2‐pyrrolidone, these low molecular weight PIAs should be semi‐rigid because of the presence of very short crystalline chains. By using the semi‐empirical Fox‐Flory relation, the extrapolated glass transition temperature equals 300°C for high molecular weight.