Regulation Of Crystallization And Degradation Behaviors Of Poly(4-Hydroxybutyrate)

Poly(4-hydroxybutyrate)(P4HB)has become a promising biomaterial because of its thermoplasticity,excellent mechanical properties,good biocompatibility and biodegradation.With the breakthrough of its chemical synthesis method,the study of P4 HB has attracted extensive attention.As implantable biomaterials,stable loss of implants can accompany new tissue growth and it is also necessary to ensure that the polymer does not suddenly release large amounts of acid degradation products.Therefore,it is of great significance to clarify the factors affecting the degradation rate of P4 HB and regulate its degradation behavior to meet different application requirements.We regulated the crystallization behavior and degradation performance of P4 HB by adding multimethyl-benzilidene sorbitol(TM6)and blending with another aliphatic polyester,poly[(ε)-caprolactone)](PCL).Firstly,the effects of TM6 on crystallization and degradation behavior of P4 HB were studied.DSC and POM results showed that TM6 could be used as heterogeneous nucleating agent to increase the crystallization temperature of and reduce the spherulite size of P4 HB.The results of weight loss and GPC measurements showed that both enzymatic and alkaline degradation of P4 HB were carried out by surface erosion,but the effect of TM6 on its degradation rate was quite different.Due to the high local crystallinity near the linear structure of TM6 and the different crystal lattice space arrangement induced by TM6,TM6-induced P4 HB crystals were difficult to be degraded by highly selective enzymes.Therefore,the addition of 0.5 wt% or more TM6 significantly reduced the degradation rate of the polymer.However,the weight loss curve and SEM results showed that the TM6-induced crystal did not affect the alkaline hydrolysis of P4 HB.Except for the addition of nucleating agent TM6,physical blending also affected the crystallization and degradation behavior of the material.When a small amount of PCL is introduced into P4 HB,PCL can induce nucleation of P4 HB and increase its crystallization rate.When the content of PCL increased enough to form crystallization itself,the crystallization of PCL gradually occupied the dominant position.SEM results showed that the degradation behavior of the blends was determined by composition,miscibility and phase structure.In addition,the block copolymers of P4 HB and PCL can be used as compatibilizers to significantly improve the compatibility of the two components in the blends.The related results expand our understanding of the degradation mechanism of polyester and have important significance for regulating the degradation rate of polyester.