形状记忆取向纤维膜的形状回复力调控

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.）.