Design and Characterization of Novel Potentially Biodegradable Triple-Shape Memory Polymers Based on Immiscible Poly(l-lactide)/Poly(ɛ-caprolactone) Blends
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In this study, covalently cross-linked network strategy has been applied to prepare new triple-shape memory polymers (TSPs) based on poly(l-lactide) (PLA)/poly(ɛ-caprolactone) (PCL) blends. The TSPs were fabricated by adding di-cumyl peroxide, with triallyl isocyanurate as a coagent for performing the cross-linking reaction. The differential scanning calorimetry (DSC) analysis demonstrated that all the PLA/PCL blends show two melting points (Tm,PCL and Tm,PLA), which can be employed as the transition temperature (Ttrans) to induce triple-shape memory behavior. The scanning electron microscopy (SEM) analysis indicated that there are two immiscible morphologies: co-continuous structure and matrix-droplet. The influence of temperature on the crystalline phase changes was analyzed by X-ray diffraction at various temperatures. The results revealed that during the heating–cooling cycle, the degree of crystallinity decreased when the temperature increased and at higher temperature, the crystallization peaks of PCL disappeared. Multiple thermal–mechanical tests were performed and the results showed that the composition ratio of the two phases plays an important role in the triple-shape memory behavior. The results confirmed that the excellent shape memory behavior was obtained for the sample containing 50 wt% PCL.