Shape Memory Behavior of Electrospun Graphene Nanoplatelets‐Reinforced Polyurethane Nanofibers Under a Constrained Recovery Approach

ABSTRACT Shape memory polyurethane (SMPU) fibers are promising for next‐generation actuators in biomedical, robotic, and aerospace systems, yet their adoption is hindered by low recovery stress, limited cyclic durability, and poor stress retention. To overcome these limitations, graphene nanoplatelets (GNPs) are incorporated at 1 and 5 wt.% into the SMPU matrix and electrospun into nanofiber membranes. GNP addition significantly increases solution conductivity, enhancing electrostatic stretching during electrospinning and reducing fiber diameter by ~46% from 540 (pure SMPU) to 291 nm (5 wt.% GNP), improving fiber alignment and uniformity. As a result, the 5 wt.% GNP‐reinforced fibers exhibit a 5.5 times increase in maximum stress, an 8.5 times increase in shape fixity stress, a six times increase in shape recovery stress, and a 13‐fold increase in retention stress after 2000 cycles, compared to pure SMPU. These enhancements are attributed to strain‐induced stiffening, restricted segmental mobility and improved phase separation in SMPU with the addition of GNP. Overall, these findings demonstrate that GNP‐reinforced SMPU nanofibers provide a robust and durable solution to the long‐standing challenges in shape memory materials, positioning them as strong candidates for high‐performance actuators in biomedical, robotic, and aerospace systems.