Chemo-thermomechanical behaviors of Enzyme-degradable shape memory composite and its heat-enzyme triggered shape memory properties

Abstract Designed with elaborated chemistry of the structure, shape memory composite (SMC) exhibits excellent biocompatibility and biodegradability, and therefore find a wide potential biomedical application. Recently, a two-constituent enzyme degradable shape memory composite (EDSMC) was reported utilizing a polyether-based polyurethane thermoplastic called Pellethane (PE) and a semicrystalline Poly (e-caprolactone) (PCL). The heat-enzyme triggered melt-crystal transition of PCL was utilized to realize the invertible “switch” of the fixing and recovery configuration. A chemo-thermomechanical 3D viscoplastic model is developed for the EDSMC aiming to provide theoretical foundation for its structure design and engineering applications. The enzyme-triggered decrystallization of crystals is captured by an energy-dependent kinetical model, and the further dissolution under enzyme activated chain-broken chemical reaction is modeled as decrease of crosslinking density. The chemo-thermomechanical constitutive model for EDSMC is established by combining the viscoplastic behaviors of the PE and that of PCL. The model is calibrated and validated by the associated experiments in the published work, and then applied to simulations of the diffusion-controlled enzyme degradation of the PCL as well as the chemomechanical behavior of the EDSMC. Some parametric examples are conducted for the heat-crystal activated shape memory properties of EDSMC. From the simulations and experiments, the enzyme-triggered dissolution of the crystals activates effectively recovery of the PCL assisted fixed configuration. The researches in this work provide the theoretical understandings for the EDSMC, and also the bio-composites characterized with the chemically triggered melt-crystal transitions.