Synthesis And Properties Of Biocompatible Polyester Based On ?-butyrolactone And Its Derivatives

Aliphatic polyester has excellent biocompatibility and degradability,and can be used as surgical sutures,tissue scaffolds,drug delivery carriers,etc.Ring-opening polymerization of cyclic lactones is an efficient and controllable method for preparing aliphatic polyesters.Compared with common aliphatic polyesters such as polycaprolactone(PCL)and polylactic acid(PLA),polybutyrolactone(P?BL)has a more suitable degradation rate and better biocompatibility in the body.Its monomer?-butyrolactone(?-BL)has a renewable green source and is cheap.Its derivative?-methylene?-butyrolactone(MBL)can also be obtained from biomass,bearing with a?-BL five-membered ring and an exocyclic double bond.In addition,P?BL and PMBL are truly chemically recyclable polyesters,which can be quantitatively depolymerized back to cyclic lactone monomers under appropriate conditions.However,?-BL is a five-membered ring with stable structure and low ring strain.It has been considered as a"non-polymerizable"monomer for a long time.In recent years,?-BL and its derivative MBL have received more and more attention.In this thesis,the organic catalyzed ring-opening polymerization(ROP)of?-BL and its derivative MBLwere investigated.This thesis mainly includes the following three sections:1.The chemoselective ROP of MBL with?-CL or?-VL was successfully achieved using the CTPB/urea binary organocatalytic system.The well-defined structures of obtained copolyesters were collaboratively characterized with 1D,2D NMR and MALDI-TOF MS techniques.The polymerization is more controllable at a low-temperature in non-polar solvent.A series of PMBL-co-PCL copolyesters with MBL incorporations in a wide range from low to high can be obtained by adjusting the feeding molar ratio of MBL/CL under optimized polymerization conditions.According to DSC and TGA tests,as the increase of the MBL incorporations,the thermal stability,the melting transition temperatures,crystallization temperatures,fusion enthalpy,and crystallinity of the PMBL-co-PCL copolyesters considerably decreased.These results suggested that the incorporation of MBL into the polymer chains disrupted the ordered arrangement of polymer chains and suppressed the crystallization of PCL components.2.The chemoselective ROP of MBL with?-VL was successfully achieved using the CTPB/urea binary organocatalytic system.The well-defined structures of obtained copolyesters were collaboratively characterized with 1D,2D NMR techniques.A series of PMBL-co-PVL copolyesters with MBL incorporations in a wide range from low to high can be obtained by adjusting the feeding molar ratio of MBL/VL under optimized polymerization conditions.Characterization of thermodynamic properties of PMBL-co-PVL copolyester by DSC and TGA.The obtained PMBL-co-PCL copolyester has a more random structure compare to PMBL-co-PVL copolyester due to the distinct different copolymerization kinetic behaviors of MBL/?-CL and MBL/?-VL as indicated by the reactivity ratios determination.3.Polybutyrolactone(P?BL)was prepared by ring-opening polymerization of?-BL with alkoxide and urea as catalyst and terephthalyl alcohol as initiator.The well-defined structure and high chain-end fidelity of obtained P?BL was characterized by nuclear magnetic resonance,SEC and mass spectrometry The P?BL with terminal hydroxyl group at both chain ends was then react with diisocyanate(MDI or IPDI)to prepare polyurethane.Polyurethane with M_w up to 285.5 kDa was obtained under optimized polymerization conditions.The chemical structure of polyurethane was characterized with NMR and SEC.