Prediction of ordered regions in nylon-6 and nlyon-6,6 glasses from heat capacity

Abstract

The conformational and intermolecular contributions to the residual enthalpy ΔHO and entropy SaO at 0 K for amorphous nylon-6 and nylon-6,6 were investigated on the basis of the derivation of a new relationship between Cp and Cv. It was found that ΔHO contains only the intermolecular enthalpy for CONH residues in amorphous nylon-6 and nylon-6,6. The conformational contribution to SaO consists, on the basis of the conformations, of 49 kinds of rotational isomeric states for nylon-6 and 2401 (49 × 49) kinds for nylon-6,6, independently of temperature. The intermolecular contributions to SaO are only due to CONH residues in these polymers. Next, through the investigation of the conformational contributions to the glass transition, the possibility of ordered regions in nylon-6 and nylon-6,6 glasses was explored. The existence of localized and ordered parts with enthalpies of 40.1 kJ mol− 1 for nylon-6 and 80.7 kJ mol− 1 for nylon-6,6 is predicted. The enthalpies of the localized ordered parts are somewhat larger than the glass transition enthalpies of 37.6 kJ mol− 1 for nylon-6 and 75.2 kJ mol− 1 for nylon-6,6, respectively.