Interfacial polycondensation. XIII. Viscosity–molecular weight relationship and some molecular characteristics of 6‐10 polyamide

Abstract

AbstractNumber‐average molecular weights were estimated by determination of endgroups on 6‐10 polyamide samples prepared by stirred and unstirred interfacial polycondensation procedures under varying conditions. Polymers made by melt and interfacial polycondensation methods obeyed the same dilute solution viscosity relationships. However, polymers from interfacial polycondensation reactions deviated in molecular weight distribution from that found for polymers prepared by the melt method. The deviation, which presents the appearance of broader than random distribution, is believed to result to a considerable degree from the presence of an unusually large low molecular weight fraction rather than a continuous distortion of the distribution curve. The interfacially prepared polyamides having the highest viscosity numbers, obtained by adjusting the concentration ratios of the two reactants, showed the least deviation from random distributions. Evidence was found for branching and even network formation in 6‐10 polyamide prepared by interfacial polycondensation as the concentration of the diacid chloride phase was increased. Branching probably occurred through acylation of amide links along the polymer chain to yield imide groups. These groups were cleaved to amide groups in the molten polymer or upon solution in sulfuric acid. Melt‐prepared, unfractionated 6‐10 polyamide followed the relationship [η] = 1.35 × 10−4 M̄n0.96, and a κ′ factor of 0.43 was found in the equation relating solution viscosity to concentration, ηnp/c = [η] + κ′[η]2c, for dilute solution determinations in m‐cresol at 25°C.