Copolymers of 1.5‐dioxepan‐2‐one and L‐ or D,L‐dilactide ‐ synthesis and characterization

Abstract

Abstract; The copolymerization of 1,5-dioxepan-2-one (DXO) with L-or D,L-dilactide in bulk has been studied, using stannous-2-ethylhexanoate as the initiator. The copolymers were characterized using *H-and 13C-NMR spectroscopy, and DSC-analysis. The molecular weight of the copolymers was measured by SEC, viscometry and lightscattering techniques. The reactivity ratios of the copolymer system were calculated using the Kelen-Tiidos method to be r l (DXO)=O,l and r2 (dilactide)=lO. No racemization seems to have taken place during polymerization as shown by the absence of stereochemical splittings in the 1 3 C-NMR spectra of the L-dilactide homopolymer. The ability of the L-LA/DXO copolymer to crystallize seems to be retained despite substantial amounts of 1,5-dioxepan-2-0ne in the composition. 1 H-and 13C -N M R spectra indicate ring-opening of the monomers by alkyloxygen cleavage. INTRODUCTIONCurrent research in the field of resorbable biomaterials often concerns copolymers of different types. Copolymer systems exhibit a broad range of properties depending on the monomers involved and the relative composition of these in the final copolymer. This makes it easier to optimize properties and thus to be able to produce a tailor-made biomaterial with respect to its application. CCC 0258-0322/92/$02.50