Critical Role of Surface-Stearoylated Cellulose on the SEBS-Based Electroactive Shape Memory Polymers for Soft Robotics Applications

Poly(styrene-b-ethylene-butylene-b-styrene) (SEBS) is a linear triblock copolymer capable of showing thermoresponsive shape memory with moderate shape fixity and recovery capabilities. However, direct thermal activation limits its applicability. Here, electroactive shape memory effects were induced by incorporating multiwalled carbon nanotubes (MWCNTs) as conductive fillers, enabling electrical heating actuation. While MWCNTs enhance shape recovery and cyclic durability, they often compromise shape fixity. To overcome this limitation, surface-stearoylated cellulose nanocrystals (SCNCs) were employed as crystalline switching domains. SCNCs self-assemble into semicrystalline structures with a broad melting range of 45–60 °C, imparting improved thermoresponsive characteristics. The inclusion of SCNCs significantly enhanced shape fixity to 79.7%, which dropped to 65% with the MWCNT alone. The shape recovery was consistently maintained at 90.3% over three consecutive cycles. Detailed analysis of the thermal, electrical, and electrothermal responses and actuation mechanisms demonstrated that the incorporation of SCNC does not disrupt the conductive network formed by MWCNTs. Instead, SCNC appears to facilitate a more efficient distribution of nanotubes, resulting in enhanced electrical and thermal performance. The optimized composite achieved 79% shape recovery under a 40 V electrical stimulus. These findings highlight the potential of SCNC-modified SEBS composites for electroactive applications in smart actuators, soft robotics, artificial muscles, and aerospace technologies.