SYNTHESIS OF ALTERNATING COPOLYMERS OF 2,2-DIMETHYLTRIMETHYLENE CARBONATE AND EPSILON-CAPROLACTAM VIA INSERTION OF EPSILON-CAPROLACTAM INTO POLY(2,2-DIMETHYLTRIMETHYLENE CARBONATE)

2,2-Dimethyltrimethylene carbonate (DTC, 1) was polymerized in toluene with dibutylmagnesium [MgBU2, 5] or aluminum tri-sec-butanolate [Al(Osec-BU)3, 6] as initiator and was used as the initiating species for the polymerization of epsilon-caprolactam (EClam, 2). The polymerization of EClam was performed in the melt at temperatures around 125-degrees-C using N-(methoxycarbonyl)-epsilon-caprolactam (3a) as a cocatalyst. By this procedure, the carbonate groups of the initiating block were converted into ester and urethane groups by formal insertion of the ring-opened lactam moiety. As a consequence, an alternating copolymer of 2,2-dimethyltrimethylene carbonate and epsilon-caprolactam was obtained by successive addition of the monomers. Evidence for this reaction route was brought about by H-1 and C-13 NMR spectroscopy. A mechanism for the formation of the copolymer is proposed.