Correlation Between The Hydroxyl Monomer Content And The Properties Of Aliphatic Polyesters

Aliphatic polyester has good biocompatibility,biodegradability,processability and thermal stability,so there has lots of development in the fields of food,agriculture,and medical treatment.Poly(ethylene succinate),PES],poly(butylene succinate),PBS] and poly(hexamethylene succinate),PHS] are all aliphatic polyesters.Pure PES,PBS and PHS have some properties defects,such as poor mechanical properties,high crystallinity,and low biodegradability,which greatly limit the application of these pure polymers in more fields.In this work,succinic acid and three different hydroxy monomers(ethylene glycol,1,4-butanediol and1,6-hexanediol)were used as raw materials,and three hydroxy monomers were added in different proportions with two combinations into succinic acid.Three series of PBS-based polyesters were synthesized by melt polycondensation method.The chemical structure,thermal properties,mechanical properties,hydrophilicity and biodegradability of the three series of PBS-based polyesters synthesized were compared and studied.The influence of hydroxyl monomer content on the properties of these polyesters were analyzed.Succinic acid,1,4-butanediol and 1,6-hexanediol were used as raw materials,pure PBS,PHS and their random copolyester-poly(butylene succinate-co-hexylene succinate)[P(BS-co-HS)] were synthesized by melt polycondensation method.It was found that the composition of the obtained copolyester was basically the same as the feed ratio of the reactants.With the increasing of HS unit content,the melting temperature,crystallinity and thermal stability of the copolyester firstly decreased and then increased.It was also found that lower melting temperature,crystallinity and higher hydrophilicity can improved Fusarium solani cutinase hydrolysis performance of the the material.The synthesized P(BS-co-HS52)and P(BS-co-HS71)in the experiment had good hydrophilicity,low crystallinity and low melting temperature,and they had the best enzymatic hydrolysis performance.Although the crystal structure of polyester would not be affected by enzymatic hydrolysis,enzymatic hydrolysis could transform the crystalline regions of polyester into non-crystalline regions,which led decreasing in its crystallinity.Using succinic acid,ethylene glycol and 1,4-butanediol as raw materials,pure PES,PBS and their random copolyester-poly(ethylene succinate-co-butylene succinate)[P(ES-co-BS)] were synthesized by melt polycondensation method.The results showed that the incorporation of BS units into pure PES not only changed the crystal structure of PES,but also slightly changed its crystallite size and crystallinity.The elongation at break of the three copolyesters were higher than that of pure PES and PBS.Fusarium solani cutinase was used to conduct enzymatic hydrolysis on the five synthetic polyesters.The enzymatic hydrolysis rate was P(ES-co-BS46)> P(ES-co-BS46)> P(ES-co-BS65)> PES> PBS.XRD and FT-IR tests showed that cutinase hydrolyzed the crystalline and amorphous regions of the polyester at the same time,and destroyed the crystal structure of the polyester.Using succinic acid,ethylene glycol and 1,6-hexanediol as raw materials,pure PES,PHS and their random copolyester-poly(hexylene succinate-co-butanediol)[P(HS-co-ES)s] were synthesized by melt polycondensation method.It was found that the crystallinity,melting temperature and melting enthalpy of copolyester were lower than pure PES and PBS.All polyesters had good thermal stability.Since the melting temperature of P(HS-co-ES51)and P(HS-co-ES32)were closed to the temperature of cutinase hydrolysis,these two copolyesters melt and aggregate under the experimental conditions,so the surface area in contact with the enzyme were reduced.This led to insufficient degradation,which reduced the apparent degradation rate.The degradation rate of all copolyesters was faster than that of pure polyesters.Among them,P(HS-co-ES13)has higher hydrophilicity,lower melting temperature and crystallinity,and the enzymatic hydrolysis rate was faster.The studies also found that the crystal structure and thermal stability of these polyesters were not affected by cutinase hydrolysis.