Synthesis And Degradability Of Chiral Polyester-imides

In recent years,polymer materials have become an important part of human life.At the same time,polymer materials are difficult to degrade and cause huge pollution to the environment.Therefore,it is very important to develop biodegradable polymer materials.Polyester-imide(PEI)synthesized based chiral amino acid is a good polymer material with high heat resistance and good mechanical properties.The introduction of amino acids makes it have excellent solubility and biodegradability.The main task of this paper is to research the thermal and degradation properties of PEI and the influence factor them by changing the structure and configuration of the introduced amino acids.The main work of this paper is divided into three parts:The first part is synthesis and characterization of chiral diacid monomers based on amino acids.Nine kinds of chiral diacid monomers were prepared by n-acylation and imidization of nine kinds of amino acids such as L-alanine with pyromellitic dianhydride(PMDA).It was characterized by melting point test,Fourier transform infrared spectroscopy(FT-IR),nuclear magnetic resonance(~1H-NMR),elemental analysis,and specific rotation test.The second part is synthesis and characterization of chiral PEI.Nine kinds of homopolymer PEI and four kinds of random copolymer PEI were synthesized by the condensation reaction of diacid monomer and 4,4'-dihydroxydiphenyl ether.The structure of PEI was characterized by FT-IR,~1H-NMR and elemental analysis.The molecular weight of PEI was tested by gel permeation chromatography(GPC).It was found that PEI had a high molecular weight.The third part is the study of the thermal properties and degradation properties of chiral PEI.The thermal performance of PEI was tested by dynamic thermodynamic analysis(DMA)and thermogravimetric analysis(TGA).The results showed that PEI has good thermal performance and high initial decomposition temperature.The glass transition temperature(Tg)of PEI is affected by the volume,rigidity and configuration of amino acid side groups.The volume effect plays a major role.The Tg of PEI decreases with the increase of the volume and rigidity of side groups.The Tg of L-configuration is slightly better than that of D-configuration.The degradation performance of PEI was studied by phosphate buffer degradation experiment.The weight average molecular weight,structural composition,film morphology and water contact angle of PEI during degradation were characterized by GPC,FT-IR,scanning electron microscope(SEM)and contact angle tester.The results showed that the degradation performance of PEI decreased with the introduction of large volume of side group,rigid group and D-configuration amino acid.