Comb-like Copolymer Bearing Branched Polylactide Side Chains: Synthesis, Characterization And Application

In this paper, the synthesis of comb-like copolymer with EC as backbone andbranched PLA as side chains by one-pot procedure was systematically studied. Aplausible mechanism for the polymerization was proposed according to themodel experiments. In addition, we studied the hydrolysis degradation andencapsulation abilities of comb-like copolymers as a drug carrier for the controlledrelease of drug.In polymerization reactions, stannous octoate [Sn(Oct)2] is the catalyst, EC ismacromolecular initiator, D,L-Lactide(LA) and2,2-bis(hydroxymethyl) butyric acid(BHB) are comonomers. The optimum amount of Sn(Oct)2is0.2times of the weightof EC, and the influence of polymerization temperature in the range of110-150℃onthe efficient incorporation of branching units was not pronounced. Compared tocomb-like copolyme（rEC-g-PLA）with EC as the backbone and linear PLA as the sidechain, EC-g-bPLA has better solubility in polar solvents. In the human bodyenvironment, namely in36.7℃, PBS buffer solution with pH=7.4, the degradationrates of EC-g-bPLA copolymers are significantly faster than EC-g-PLA, and raisingthe content of branching units increases the degradation rate. EC-g-bPLA has goodencapsulation ability. When encapsulating nonpolar object molecules, such as Pyreneand Thiomichlers ketone (TMK), those encapsulation ability and release ability arebetter than those of EC-g-PLA.