Modification Of Poly(Propylene Carbonate)

Though carbon dioxide（ CO₂） is the main greenhouse gas, it is an abundant, inexpensive, and renewable carbon resource. Therefore, the catalytic transformation of CO₂ into biodegradable poly（propylene carbonate）（PPC） by alternating copolymerization with propylene oxide（PO） has drawn much attention in view of economic. It possesses excellent adhesion, transparency and low permeability for oxygen and water, and it burns gently in air only producing CO₂ and water. So PPC has a wide range of applications such as binders, biological medicine and packing material. However, the practical application of PPC has been limited by its a kind of amorphous polymer, and the thermal performance and mechanical properties are too poor to meet the requirement of the applications, the compatibility of PPC with most polymer is poor because of no reactive functional groups in the main chain. Therefore, many approaches have been developed to improve the thermal and mechanical properties of PPC, such as endcapping, chain extension, terpolymerization and cross-linking.The contributions of this thesis include the following two aspects, first,the itaconic anhydride（IAn）, was incorporated into poly（propylene carbonate）（PPC） by solution-blending, the second, The synthesis of amino-functionalized poly（propylene carbonate）（PPC） by terpolymerization of carbon dioxide（CO₂）, propylene oxide（PO）, and N,N-Dibenzyl Amino Glycidol（DBAG） following the removal of benzyl groups.1. PPC was solution-blended with IAn in weight proportions ranging from 2.5 wt% to 10 wt%. The mixing was heating stirring in the round bottom flask at 60℃ for 4h in chloroform, the precipitates solution of chloroform from ethanol are whole mass polymers. The precipitates were dried in vacuum at 50℃ for 24 h. After drying, it was calefactioned in vacuum at 100℃ for 2h. Get the final product was named PPC/IAn. The results show that the addition of IAn improves the molecular weights obviously. In particular, the number average molecular weights of PPCIAn can be achieved 60320g/mol. The results of the thermal stability and mechanical properties tests showed the thermal stability and mechanical properties of PPCIAn are better than those of PPC. Especially, the Tg of PPCIAn can be up to 39.4℃, the tensile strength can reach 48.5 MPa, which is much higher than those of PPC（ 34.3℃ and 4.3MPa）. In addition, the degradability of PPCIAn was determined in the phosphate buffer solution（PBS） of pH 7.4 at 37 ℃ for 10 weeks. PPCIAn exhibit high degradability compared with PPC. After 10 weeks, the weight loss increased up to 12.7%, which was significantly higher than that of PPC of 4.3% and the results further confirmed by SEM.2. The synthesis of amino-functionalized poly（propylene carbonate）（PPC） by terpolymerization of carbon dioxide（CO₂）, propylene oxide（PO）, and N,N-Dibenzyl Amino Glycidol（DBAG） following the removal of benzyl groups. The results show that the protecting groups of DBAG can be removed by CAN completely with no impact on the molecular weight of PPC. The amino group content of PPC-NH₂ polymers could be adjusted by varying the molar ratio feed of DBAG comonomer, and maximum Amino group content was 3.2%. The results of the hydrophily tests showed the hydrophily of PPC-NH₂ is better than those of PPC. Contact angles of PPC-NH₂ was 60.2 °, Contact angles of PPC was 70.2 °. In addition, the degradability of PPC-NH₂ was determined in the phosphate buffer solution（PBS） of pH 7.4 at 37℃ for 10 weeks. PPC-NH₂ exhibit high degradability compared with PPC. After 10 weeks, the weight loss increased up to 17.2%, which was significantly higher than that of PPC of 4.3% and the results further confirmed by SEM.