Synthesis And Properties Of Novel Polyesters From Derivatives Of Levulinic Acid

Synthesizing polymers from renewable biomass resource is one feasible way to solve the problems of environment pollution and resource shortage in current polymer industries.In this work,polymer from diphenolic acid(DPA)and isophthaloyl chloride(IPC)was synthesized by interfacial polycondensation.Diphenolic acid was synthesized from a platform chemical-levulinic acid(LA)which derived from biomass resource.The reaction mechanism,mathematical model,performance of the polymer,mechanism of the thermal degradationand the modified polymer were studied systematically.Poly(DPA-IPC)including DPA and IPC was obtained by interfacial polycondensation with tetrabutyl ammonium chloride(TBAC)as phase transfer catalyst.It was found that a large mass of capsules were formed at the beginning of the reaction with various solvent as organic phase examined but the capsule morphology and reaction results depended on the solvents.The effect of the solvents on the reaction was interpreted from the interaction between the polymer and the solvent according to the mechanism.The reaction conditions were optimized,and poly(DPA-IPC)with high intrinsic viscosity(1.71 dl/g)was prepared in high yield (95%)under the optimal condition.The physical model of the reaction system can be derived from the reaction mechanism.The reaction-diffusion equations of the local monomer concentration in the organic phase and the unreacted end groups of the growing polymer were obtained according to a series of assumptions.The numerical solutions of these equations were gained through difference method and chasing method.The concentration variability of IPC with time from analog data coincided with the experimental data.Thus it can be seen that the mathematical model is appropriate to this reaction system.The change of concentration of monomers and polymer with diameter of the capsules was found by the analog result.Through changing the model parameters,it was found that the diffusion of monomers from aqueous phase and organic phase to the reaction zone was the rate-determining step.In the interest of thermal performance of poly(DPA-IPC),the glass transition temperature(159℃)and the curve of thermal degradation were obtained by means of DSC and TGA,respectively.Being compared with poly(BPA-IPC),the thermal performance of poly(DPA-IPC)decreased.By means of PGC/FTIR,TGA/FTIR,it was found that the mechanism of weight loss at the first,stage was the existence of the pendent carboxyl group.The thermal kinetic was obtained with the Freeman-Carroll method and Coats-Redfern method.The NaOH solution of poly(DPA-IPC)was titrated by aqueous HCl solution.The pH value of solution gradually decreased with the addition of HCl solution.In addition,the reduced viscosity of solution was increased with the decreasing concentration of poly(DPA-IPC).These behaviors are typical polyelectrolyte.Poly(DPA-IPC)was stable in aqueous basic solution.In brief, poly(DPA-IPC)can be used as polyelectrolyte.The polymers from IPC and the esters of DPA which were from the reaction of DPA and methanol or ethanol were synthesized by interfacial polycondensation with TBAC as phase transfer catalyst.Firstly,it was approved that the aliphatic ester was stable in NaOH solution.Then,the reaction mechanism of this reaction system was gained through the variability of yield and intrinsic viscosity in various solutions and it was proved from the phenomenon that the polymer with higher yield and intrinsic viscosity was.gained with higher reaction temperature.The glass transition temperature of polymers from methyl ester or ethyl ester of DPA and IPC was 149.4℃and 140.5℃,which was obtained through DSC and TGA,respectively.The temperature of thermal degradation of the polymers from esters of DPA and IPC is 300℃.The mass loss is about 70%.The thermal performance is better than that of poly(DPA-IPC).The thermal performance and the processing of the polymers from DPA or DPA derivates were not good,so the copolymers from BPA and DPA or DPA derivates were synthesized.In DPA/BPA/IPC reaction system,the change of the reaction degree and the composition with stir speeds and reaction temperature was studied and it could be found that the block copolymer was apt to be gained.In the reaction system of esters of DPA and BPA and IPC,the composition of copolymer was close to the molar ratio of the monomers because the esters of DPA were hydrophobic.The glass transition temperature and thermal decomposition curves of the copolymers with molar ratio of DPA and BPA from 2/98 to 10/90 were obtained by means of DSC and TGA.The glass transition temperature decreased with the increasing addition of DPA, the lowest temperature was 163.5℃.The temperature of thermal degradarion was 380℃when the molar ratio of DPA and BPA was 2/98,but it greatly decreased to 280℃when more DPA was added.The glass-transition temperature and thermal decomposition curves of copolymers from esters of DPA and BPA were given by means of DSC and TGA.The glass transition temperature decreased with the increasing addition of esters of DPA.The temperature of thermal degradarion was greater than 380℃when the addition of esters was 10%.It gradually decreased with the increasing addition of esters.Thus it can be seen that different requirement for materials can be satisfied through changing the molar ratio of monomers.Because the polymers from DPA and DPA derivates are not biodegradable,so the biodegradable copolyester was obtained fromε-caprolactone(ε-CL)andγ-valerolactone(γ-VL)which was from levulinic acid by bulk ring-opening copolymerization.The catalysts such as tetraphenyl tin,aluminium isopropoxide and boron trifluoride etherate complex were used to catalyze the copolymerization.In addition,the copolyester can be given by copolycondensation after monomers were hydrolyzed by phosphoric acid.Boron trifluoride etherate complex was chosen as the catalyst because the catalytic activity was the best among the catalysts.The copolymer with high yield can be gained under optimized reaction conditions.The molecule weight,composition and melting point of the copolymers were characterized by means of GPC,~1H-NMR and DSC,respectively.The reactivity ratio ofε-CL andγ-VL was estimated as 17.6 and 0.0078,respectively,by K-T method.