C-13 NMR spectra of nylon 6/12 copolymers and related model compounds

The C-13 NMR spectra of model mono- to tetra-amides containing CO, (CH2)(5) and (CH2)(11) groups in varied sequential arrangements have been used to r einterpret assignments previously proposed for signals in the spectra of ny lon 6/12 random copolyamides. From the CO signal intensities, the mean nylo n 6 and nylon 12 home-unit block lengths have been determined in copolyamid es prepared by rapid (ca. 15 min) activated anionic lactam copolymerisation at 180 degrees C. The results are virtually identical with published data for equilibrium copolymers of similar co-unit ratios made by hydrolytic pol ymerisation at 260 degrees C in reaction times > 144 h. Maximum sequential randomness occurs at ca. 50-60 mol% nylon 6 component, coinciding with mini ma in the thermal and solid-state properties. (C) 2000 Elsevier Science Ltd . All rights reserved.