document: A hydroxyl-functionalized poly(butylene succinate) based polyester was prepared by conventional polycondensation of benzyl-protected dimethyl malonate and 1,4-butanediol (Scheme 2(a)) [24a]. Yao et al. reported on the direct polycondensation of l-lactic acid and citric acid with the formation of poly[(l-lactic acid)-co-(citric acid)], obtaining a polyester oligomer with both pendant carboxylic and hydroxyl groups [24b]. This PLCA oligomer was reacted with dihydroxylated PLLA as a macromonomer, yielding a PLCA–PLLA multiblock copolymer as shown in Scheme 2(b). While lipases have been investigated for the ring-opening polymerization (ROP) of cyclic ester monomers [25,26], they have also been used for the preparation of polyesters by polycondensation reactions. The advantage of this technique is that these enzyme-catalyzed reactions proceed without protection of the pendant functional groups. In this field, hydroxyl-bearing polyesters have been synthesized by the copolymerization of divinyl adipate with various triols (e.g. glycerol, 1,2,4-butanetriol) as represented in Scheme 2(c) [27] and by copolymerizations of 1,8-octanediol with adipic acid and several alditols [28]. Very recently, several α-hydroxy acids derived from amino acids were homo- and copolymerized with lactic acid by polycondensation in bulk without protected monomers (Scheme 2(d)) [29]. Biodegradable polyesters with various pendant groups were obtained, although the molecular weights remained low (1000–3000gmol−1).
extractive_keyphrases: adipic acid alditols amino acids biodegradable polyesters citric acid copolymerization copolymerizations cyclic ester monomers dihydroxylated plla dimethyl malonate divinyl adipate glycerol lactic acid lipases monomers plca oligomer plca–plla multiblock copolymer polycondensation polyester polyesters rop triols
abstractive_keyphrases: 1,2,4-butanetriol 1,4-butanediol 1,8-octanediol enzyme-catalyzed hydroxyl-bearing polyesters l-lactic acid polyester oligomer poly[(l-lactic acid)-co-(citric acid)] ring-opening polymerization α-hydroxy acids