形状记忆取向纤维膜的形状回复力调控

Regulating the Shape Recovery Stress of Aligned Fibrous Mats with Shape Memory Capability

将生物可降解左旋聚乳酸(PLLA)与聚羟基丁酸戊酸共聚酯(PHBV)通过稳定射流电纺(SJES)技术制备取向的PLLA/PHBV复合纤维,并评价了其形状记忆性能。基于形状记忆聚合物的形状编程原理,对该PLLA/PHBV取向纤维进行不同应变的高温拉伸和低温固定处理,得到不同拉伸应变的取向纤维,并对其形貌、拉伸力学、分子取向度及形状回复力等进行表征测试。结果表明:利用SJES技术制备的PLLA/PHBV取向纤维具有良好的形状记忆性能,形状固定率和形状回复率分别为(96.79±0.64)%和(71.64±8.87)%。经不同拉伸应变编程处理的PLLA/PHBV取向纤维的形状回复应力从0(ε=0)分别增加到(5.32±0.32)MPa(ε=40%)、(7.63±0.26)MPa(ε=70%)和(9.24±0.13)MPa(ε=100%),证明通过改变拉伸应变可以实现对取向纤维形状回复力的调控。

Shape memory polymers(SMPs)are smart polymeric materials that have the capability to return from a deformed state(temporary shape)to their original(permanent)shape in response to an external stimulus.Engineering those biodegradable SMPs into fibrous form will thus offer new functionalities to the fibrous implants(e.g.,intelligent surgical sutures and tissue-engineered scaffolds)in the field of biomedicine.However,up to now very few has been done in terms of making use of the shape recovery force of SMPs.On the basis of an already established stable jet electrospinning approach,aligned composite fibers of PLLA/PHBV consisted of biodegradable poly(L-lactic acid)(PLLA)and poly(3-hydroxybutyrateco-3-hydroxyvalerate)(PHBV)were prepared in this study.Thereafter,shape memory effect of the electrospun aligned PLLA/PHBV fibers was evaluated.Based on the shape-programming principle of SMPs,the prepared aligned PLLA/PHBV fibers were stretched at high temperature and cooled down to fix the shape/strain,giving rise to the aligned fibers with different tensile strains for regulating the shape recovery stress.The morphology,tensile properties,molecular orientation and shape recovery of the programmed fibers were systematically characterized.The results show that the aligned PLLA/PHBV fibers possess good shape memory performance,and the shape fixing and shape recovery rates are(96.79±0.64)%and(71.64±8.87)%,respectively.Shape recovery stress of the aligned PLLA/PHBV fibers programmed at different tensile strains was measured from 0(ε=0)to(5.32±0.32)MPa(ε=40%),(7.63±0.26)MPa(ε=70%),and(9.24±0.13)MPa(ε=100%),confirming the feasibility of tuning shape recovery stress via controlling tensile strain of the aligned fibers.This study provides a basis for future investigations on the shape-recovery effect of shape-memory aligned fibers for the regulation of cell function in engineering structurally anisotropic tissues(such as tendons,ligaments,etc.).