Polydopamine-engineered cellulose nanocrystals for NIR-triggered shape memory waterborne polyurethane composites

The development of sustainable and intelligent polymer composites is imperative for advancing fields such as flexible electronics and soft robotics. This study addresses the interfacial incompatibility between hydrophilic cellulose nanocrystals (CNCs) and a waterborne polyurethane (WPU) matrix by implementing a bio-inspired polydopamine (PDA) surface modification strategy. PDA-coated CNCs (PCNC) were synthesized via in-situ self-polymerization and incorporated into WPU to fabricate functional nanocomposite films. Comprehensive characterization confirmed the successful deposition of a PDA layer on CNCs, which enhanced interfacial adhesion through hydrogen bonding and π-π interactions. The optimized composite, containing 0.8 wt% PCNC, exhibited a synergistic improvement in mechanical properties, achieving a tensile strength of 4.5 MPa and an elongation at break of 1600%, alongside enhanced thermal stability. Furthermore, the embedded PDA conferred efficient photothermal conversion capability. Under 808 nm near-infrared light irradiation, the composite demonstrated rapid and reversible shape memory behavior, recovering its permanent shape within seconds. The design of this PDPU composite establishes a sustainable pathway for fabricating multifunctional smart materials with potential applications in adaptive devices, smart textiles, and remotely actuated systems.