Synihesis And Characterization Of The Biomimetic Zwitterionic Polymer

Polylactic acid(PLA) nowadays has been widely used for biomedical applications because of its good biocompatibility and biodegradability, suggesting that PLA can easily be metabolized without side effects. However, PLA is hydrophobic due to containing large amounts of ester bond, not soft enough and lacking of flexibility and intensity. As a result, it does not meet the requirements of biomedical materials and hydrophilic drug carrier.Zwitterionic polymer, a membrane-like polymer containing equal amounts of positive and negati1 e charges, has been received considerable attention owing to its good biocompatibility, anti-blood cell adhesion, anti-protein adsorption and hydration properties.To improve the hydration and anti-blood cell adhesion of PLA, we modified PLA with zwitterionic polylactic acid through different methods.The main work of the paper is as follows:Firstly, we synthesized the polymer by L-lactide ring-opening using the glycerophosphoryl extracted from egg as initiator. We analyzed the structures of the polymers by 1H NMR, and the molecular weight of the products were analyzed by gel permeation chromatography(GPC).Secondly, we synthesized the sulfobetaine polylactic acid via three paths.(1) Zwitterionic initiator was prepared by the reaction of N- methyl diethanol amine 1,3-propane. And then the sulfobetaine polylactic acid was obtained by ring-opening polymeration.(2) We synthesized the polymer by L-lactide ring-opening use the N-methyldi- ethanolamine as initiator, and then the polymer reacts with the 1,3-propanesultone to obtain the sulfobetaine polylactic acid.(3) Zwitterionic polymers were prepared by Click reaction. Firstly, zwitterionic azido was synthesized by using 3-dimethylamino-1- propanol, methanesulfonyl chloride, sodium azide and 1,3-propane. Secondly, the polymer was synthesized by L-lactide ring-opening using 2-methyl-2-acetylene methoxyl-1,3-propanediol as initiator. Last, the product was obtained by the click reaction to combine these two parts together. The products were analyzed by 1H NMR and GPC.Thirdly, PEO-PLA with cations was prepared by click reaction. The Zwitterionic terminal alkynes was prepared through the reaction of the propargyl bromide and N- methyl-diethanolamine. Then the macromolecular initiator PEO-MDEA was synthesized through the click reaction. At last zwitterionic PEO-PLA was prepared by lactide ring-opening using the PEO-MDEA as the initiator.