Novel double-networked polyurethane composites with multi-stimuli responsive functionalities

Abstract

Simultaneously improving the strength and toughness of shape-memory polymers as well as creating multi-stimuli responsive capabilities for them via a bio-based approach is significant for broadening their applications. In this work, a functionalized microcrystal cellulose material as a dual-functional modifier that served as a cross-linker and reinforcement agent was synthesized for building a multi-stimuli responsive shape-memory polyurethane (SMPU) composite. In the meantime, a rhodamine derivative, a popular fluorophore, was applied as a novel toughening modifier to extend the SMPU ductility and sensitivity in addition to generating a photo-response for the SMPU composite. The resulting heterogeneously assembled double-network provides excellent thermo- and photo-stimuli responsive capability with excellent reversible photochromic behaviors. The results indicated that the SMPU composite showed 200% and 300% increase in strength and elongation at break, respectively, in comparison with the unmodified PU. This study led to initial findings in ensuring simultaneous enhancements in both strength and toughness as well as multiple functionalities of SMPU composites. It laid a significant foundation for their broad applications, such as in the fields of sensors, self-fitting tissue scaffolds, and switchable devices.