Polymerization of Lactams: 57. G.l.c. and n.m.r. analysis of the anionic copolymers of 2-pyrrolidone with 6-caprolactam and 8-octanelactam

The activated anionic copolymerization of 2-pyrrolidone (PD) with 6-caprolactam (CL) or 8-octanelactam (OL) proceeds even above the ceiling temperature for PD homopolymerization. At high temperatures, the copolymerizations are accompanied by the depolymerization of PD sequences, which is more pronounced with the copolymers with CL. The copolymers obtained probably exhibit a constitutional heterogeneity and contain considerable amounts of low-molecular weight fractions. This may be the reason why the content of comonomers in the prepared copolymers determined by g.l.c. did not agree with that found by ¹H n.m.r. or ¹³C n.m.r. spectroscopy. The copolymers with CL had in part a block structure and also an alternating character, depending on temperature and polymerization time, while random copolymers were obtained at high temperatures. The copolymers with OL tended mostly to alternation.