Cyclopolymerization. I. An electron spin resonance study of irradiated N‐methyldimethacrylamide

The mechanism of cyclopolymerization was studied by measuring ESR spectra of propagating radicals produced in Nmethyldimethacrylamide by gamma irradiation from /sup 60/Co. Polymerization of this compound gives a five- membered ring as a main repeating unit and a six-membered ring as a minor repeating component. Results from the ESR study indicate that the rate deternaining step of the solid-state cyclopolymerization of N- methyldimethacrylamide is an intramolecular cyclization reaction and that the cyclization proceeds in a stepwise way. (LK) The molecular weight distribution of polyethylene produced by radiation was calculated according to a kinetic scheme. The calculated molecular weight distribution was compared with the results deduced from gel-permeation chromatography. The observed distribution curve from GPC was broader and showed a lower degree of polymerization than the calculated one. Discrepancies between observed and calculated curves can be explained if the polymer contains nonsteady-curve products and if the reaction mechanism includes chain transfer to dead polymer. By this reaction long-chain branching would occur. Several long-chain branches per polymer molecule were indeed found, as inferred from solution properties. (auth)