Fabrication And Characterization Of Shape Memory Poly(ε-Caprolactone) Foams

With fast developments of shape memory polymers, they have been playing important roles in various areas such as aerospace, biomedical engineering and smart textile. SMPs can serve as actuators, smart capsules and scaffolds for tissue engineering. Among different shape memory polymer forms, shape memory polymer foams(SMPFs) are attracting great attention for its high compression ratio, which allows them to be used for minimally invasive surgeries. The most ideal characteristic for most applications is biodegradability to avoid second invasive surgery. Thus, we introduce poly(ε-caprolactone)(PCL) with regenerated silk fibroin(RSF) as functional phase to improve the biodegradability and hydrophily.Solid state foaming was selected as the foaming method to fabricate shape memory PCL foams with RSF. SEM, DSC, DMA and swelling equilibrium test were applied to characterize basic properties of PCL foams. As the addition of crosslinking agent, the porosity and crosslinking density increase, while transitional temperature and crystallinity decrease. Increase in weight percentage of RSF results in decreased crystallinity and increased transitional temperature.Compressional tests including room temperature compression and high temperature compression tests were performed on different shape memory PCL foams. As a result, effective elastic modulus and yield stress decrease as concentration of crosslinking agent increases. The adding of RSF improves the mechanical properties of PCL foams greatly. Computational models were built based on differential method in meso-mechanics and empirical equation based on vast experiments. Computational results of compression behavior of shape memory PCL foams were compared with experimental results with consistency.Shape recovery tests were performed as well. The results of shape fixity ratio and recovery ratio show that shape memory PCL foams have great shape memory properties. Full shape recovery of pure shape memory PCL foams can be completed and solvent actuation cycles were employed as well.