Mechanically Robust, Degradable, Catalyst-Free Fully Bio-Based Shape Memory Polyurethane: Influence of a Novel Vanillin–Alaninol Chain Extender

In this study, a new family of fully bio-based shape-memory polyurethanes (Bio-SMPUs) was synthesized. The Bio-SMPU prepolymer was derived from abietic acid-based diisocyanate (AADI), and the novel chemical structure of the chain extender (CE) was derived from vanillin and alaninol amino acid (DVA). The microphase separation, and physical and mechanical properties of these new Bio-SMPUs were studied to determine the effect of varying molar ratios of AADI/polycaprolactone (PCL)/DVA. With proper shape programming via dynamic mechanical analysis (DMA), the shape-memory properties of the synthesized Bio-SMPU were investigated. It was found that the shape fixing rate (Rf) was greater than 98%, while the shape recovery rate (Rr) was around 85% in the first cycle. In the following cycles, Rf and Rr values were found to be greater than 90%. In addition, in vitro hydrolytic biodegradation of the Bio-SMPUs was also investigated. Within eight weeks, the maximum biodegradation weight loss reached around 71%. The physical and mechanical properties of these novel Bio-SMPUs were comparable to what were reported previously for SMPUs synthesized with conventional petroleum-derived diisocyanates and chain extenders. This study outlined a new route to produce a completely bio-based SMPU with high mechanical properties and excellent shape-memory performances that were suitable for a wide range of practical applications.