Design And Synthesis Of Functional Biodegradable Polyesters

By molecular design,a biodegradable aliphatic polyester with functional groups have been synthesized.First of all,a hydroxy-functional polyester was prepared by ring-opening polymerization of lactones;N1,N2-bis(tert-butoxycarbonyl)-L-lysine was utilized to add protecting group,after deprotection with trifluoroacetic acid,amino-functionalized polymer was prepared.Finally,biological elastomers were obtained as the reaction product of amino-functional plyester and epoxy-groups macromonomer.Infrared absorption spectroscopy(FTIR),proton nuclear magnetic resonance(1H-NMR),differential scanning calorimetry(DSC)and thermal gravimetric analyzer(TGA)were used to characterize the structure and the performance of the product.Experimental results show that the highest yield can be achieved with a monomer molar ratio of 1:1,catalyst rate of 1wt%and at the temperature of 140℃ for 4h.The amount of initiator used in this experiment is the amount of controlling the molecular weight at about 10,000.Curing results shows that:the best elastomer was obtained with reaction temperature at 120℃ for 48h,and with the accelerant amount of 1wt%.The FTIR figure shows the existence of ester group,methylene group and hydroxyl group in both polymers.It can be seen in the 1HNMR spectrum of polycaprolactone that the chemical shift characteristic peaks of the different hydrogen,and the area of each peak is proportional to the number of hydrogen atoms in different chemical environment,which in turn corresponds to the structure.The above characterization confirms that the ring-opening reaction dose occurred between the caprolactones,thereby a polycaprolactone homopolymer was produced.Similarly,in IRand 1HNMR spectrums of protecting groups and amino-functionalized polymers,an obvious change can be observed about presence and disappearance of characteristic peaks corresponding to the tert-butoxycarbonyl group,indicating that in the reaction of this experiment the lysine protecting group was successfully grafted on chain ends of polyester,and also proving the successful removal of the protecting group,so as to produce an amino functional polyester.Thermal analysis shows that in the homopolymer system,polycaprolactone with different terminal groups have glass transition temperatures below-60 ℃,and a crystal melting peak at 50 ℃.But the corresponding elastomer has no melt crystallization peak and the glass transition temperature appeared at 12℃.In copolymer systems,it is found that copolymers of different monomers ratio and different end groups resulted in different glass transition temperatures,which are in the range of-45 ℃～-35 ℃;while the glass transition temperature of the corresponding elastomers is 16℃.In summary,the characterization results indicate the successful synthesis of group-functional polycaprolactone and poly(glycolide-caprolactone)copolymer,as well as biological elastomers with certain desired properties.