RANDOM COPOLYMERS OF 1,5-DIOXEPAN-2-ONE

Copolymers of 1,5-dioxepan-2-one (DXO) and epsilon-caprolactone (epsil on-CL), delta-valerolactone (delta-VL) or L-lactide (LLA) have been sy nthesized and characterized. High molecular weight copolymers were obt ained using stannous-2-ethyl hexanoate as catalyst in bulk. Reactivity ratios for the copolymerization of DXO and delta-VL were determined a t 110 degrees C as r(VL)=0.5 and r(DXO)=2.3. At high conversion, depol ymerization of delta-VL occurred, resulting in lower molecular weight and variations in the copolymer composition. Physical properties, such as crystallinity and melting temperature of the DXO-copolymers proved to be strongly dependent on the choice of comonomer and on the molar composition of the copolymers. DXO appears to be incorporated into the poly-epsilon-caprolactone (PCL) crystals and to some extent into the poly-delta-valerolactone (PVL) crystals, resulting in a more gradual d ecrease in crystallinity with increasing amount of DXO.