a polycarbonate - polyester block copolymer includes a polycarbonate block and a polyester block , each having specific structures . the block copolymer can be prepared , at least in part , from renewable feedstocks . in some forms , the block copolymer includes biodegradable segments that facilitate structural breakdown of objects molded from the block copolymer . methods of preparing the block copolymer are described as are compositions that include it and articles prepared from it .