Synthesis Of Modified Aliphatic Polyesters Via Compolymerization

Polymer materials are crucial importance to our society,but their post-treatment may cause harm to the environment.Aliphatic polyesters are considered as a potential sustainable substitute of petroleum-based polymers owing to great biocompatibility and biodegradability,therefore it is widely used in daily applications(clothing,packaging materials to agriculture and biomedicine,etc).The demand for aliphatic polyesters materials increases with the rapid development of social economy,and the requirements of performance become more and more demanding.On the other hand,aliphatic polyesters have low molecular weight,poor mechanical properties and strong hydrophobicity,which affect their practical application.It is great significance to the modification of aliphatic polyesters materials.Therefore,it is very necessary to develop the approaches for the synthesis of modified aliphatic polyesters by terpolymerization and graft copolymerization to meet the current requirements.The work of this thesis includes three parts:Firstly,aliphatic polyester PCLPAGL with hydrophilic segments was prepared by ROP of?-CL,PA and GL,and the mechanism of ROP was investigated;Second,aliphatic polyester P(PA-ECH)with functional groups was synthesized by ROP of ECH and PA,and the activity of the functional groups was discussed;Finally,the graft polymer P(PA-ECH)-g-PMMA was synthesized from P(PA-ECH)and MMA.The one-pot copolymerization of PA,ECH and vinyl monomers(such as HEMA,DAAM and NIPAM)was carried out,and the possible mechanism of this process was confirmed.1.The aliphatic polyester PCLPAGL with hydrophilic segments was prepared by ROP of?-CL,PA and GL catalyzed by ZnGA,and the mechanism of ROP was discussed.The results showed that copolymer viscosity decreases with the addition of PA and GL.It was found that hydrophilic properties of PCL could be effectively improved by the copolymerization of?-CL,PA and GL,the contact angle of PCLPAGL could reach 12.43°.The self-assembled ternary copolymer micelles of PCLPAGL4 were worm-like,and the particle size was measured about 532nm.The mechanism showed that single ZnGA could not catalyze the ROP of?-CL,but GL was used as initiator to coordinate,activate and ring-opening with ZnGA to form active center Zn-O bond,which lead to the ring-opening of PA and?-CL,the formation of random copolymer PCLPAGL.2.The aliphatic polyester P(PA-ECH)was prepared from PA and ECH catalyzed by ZnGA.The activity of C-Cl bonds on the side group of P(PA-ECH)was verified with the addition of TEMPO.The results showed that TEMPO can successfully capture the free radicals generated from P(PA-ECH),and the structure of resulted polymer was verified by ~1H NMR.The conversion rate of TMEPO can reach to48.00%by changing the amount of ZnGA.The graft copolymerization of aliphatic polyester with TMEPO was also investigated.Next,we further investigated the role of ZnGA in graft polymerization.It was found that the yield of vinyl monomers and the conversion of vinyl monomers increased with the addition of ZnGA.3.The graft copolymerization of aliphatic polyester P(PA-ECH)and MMA catalyzed by ZnGA was carried out.The change of molecular weight of the polymer under different feed ratios was discussed.The experimental results show that the molecular weight of the polymer increases with the increase of MMA content.In terms of reaction mechanism,under the action of ZnGA,C-Cl bonds of P(PA-ECH)break to form free radicals,then initiate the graft copolymerization of MMA with aliphatic polyesters,which has been verified by ~1H NMR.Then,the one-pot copolymerization of PA,ECH and HEMA,DAAM and NIPAM with mixed monomers was carried out using ZnGA.In terms of reaction mechanism,the synthesis of P(PA-ECH)from PA and ECH catalyzed by ZnGA,and the graft copolymerization with vinyl monomers owing to the free radicals produced form C-Cl bond breaking by ZnGA.The experimental results show that HEMA,DAAM and NIPAM can be copolymerize with PA and ECH,which further expands the one-pot copolymerization for the synthesis of grafted copolymers of aliphatic polyesters.The hydrophilic properties of the copolymer P(PA-ECH-HEMA)increased with the increase of the amount of HEMA.The GPC show that the molecular weight of polymer increased with the increase of vinyl monomer content.