Design,Sythesis And Properties Of Polyester Materials Based On Citricacid

Citric acid is an important biological resource,which is abundant in China.Dimethyl acetone dicarboxylate,a unique bio-based material,was obtained from citric acid by further processing.This paper presents three kinds of high T_gpolyesters from citric acid,which are divided into three themes:renewable aromatic thermoplastic polyester,UV curable cross-linking materials,and reprocessable bio-based Vitrimer materials.1.Aromatic monomer was synthesized from natural citric acid and cinnamaldehyde 2,3-diphenyl diethyl terephthalate（DDB）.A series of bio-based homopolyester materials were obtained by melt polymerization of the monomer with common renewable diols.The results of NMR and single crystal X-ray diffraction were compared The stereoscopic structure of DDB was studied by X-ray diffraction.The structure and thermodynamic properties of homopolyester were analyzed by Fourier transform infrared spectroscopy,nuclear magnetic resonance spectroscopy,UV-Vis measurement,thermogravimetric analysis and differential scanning calorimetry.The results show that the citric acid monomer DDB has enough rigidity and thermal stability,which can significantly improve the glass transition temperature of the polymer,and the obtained polyester material has strong UV shielding effect.2.Tetraolefin monomer tetra-2’-methylallyl-3,7-dihydroxy-[3,3,0]bicyclo-2,6-octadien-2,4,6,8-tetracarboxylate（OTMA）was synthesized from dimethyl acetone dicarboxylate（DAC）,a citric acid based chemical raw material,by multi-step reaction.And OTMA was further methylated and synthesized another tetraolefin monomer tetra-2’-methylallyl-3,7-dihydroxy-[3,3,0]bicyclo-2,4,6,8-tetramethyl-2,6-octadien-2,4,6,8-tetracarboxylate（TM-OTMA）.The monomers mixed with common sulfhydryl reagents,then the photoinitiator benzoin dimethyl ether（DMPA）was added.A series of materials were obtained by heating and ultraviolet irradiation,and a series of chemical,thermal and mechanical characterization were carried out by FTIR,¹H NMR,¹³C NMR,DSC,TGA and mechanical tensile test.The results show that TM-OTMA changes the thermal instability of OTMA through methylation.TM-OTMA series materials have the characteristics of thermal stability and high rigidity.3.Transesterification is a classical organic chemical reaction and a reversible dynamic covalent reaction.Tetramethyl 3,7-dihydroxy-[3,3,0]bicyclo-2,6-octadiene-2,4,6,8-tetracarboxylate（OTM）was synthesized from dimethyl acetone dicarboxylate（DAC）,a citric acid based chemical raw material.A series of bio-based dynamic covalent polyester materials were prepared by mixing OTM with various renewable diols.The chemical properties,thermal,mechanical and optical characterization,repeated processing and degradation-recycle experiments were carried out on these materials by FTIR,¹H NMR,¹³C NMR,DSC,TGA,UV-Vis and mechanical tensile test.The results show that OTM is a kind of bio-based dynamic transesterification crosslinking monomer without catalyst.The material has transparency,good strength and rigidity,and is easy to be reprocessed,degraded and recycled.