Synergistic Enhancement of Electrical Conductivity and Mechanical Properties of Shape Memory, Self-Healing, and Reprocessable Polyurethane/Carbon Nanotube Composites Via Constructing Self-Reinforced Segregated Structure

Abstract

Conductive polymer composites (CPCs) with segregated structures have attracted significant attention due to their low filler content and high conductivity, but challenges remain in simultaneously enhancing electrical conductivity and mechanical properties caused by interfacial defects and filler agglomeration. Here, a novel self-reinforced segregated structure is constructed in dynamic Diels-Alder cross-linked polyurethane/carbon nanotube (PUDA/CNT) composites via infrared (IR) irradiation and hot pressing. PUDA microspheres with a size distribution within 100-300 μm are first synthesized by the prepolymerization-suspension method, which are then mixed with CNTs to form composite microspheres. IR treatment of composite microspheres embeds CNTs tightly into the microsphere surface to form a CNTs/PUDA layer, improving the interfacial adhesion and leading to the formation of a dense conductive network (self-reinforced segregated structure) after hot pressing. The results show that the IR-treated PUDA/CNT-3wt% composite exhibits an electrical conductivity of 58.5 S/m, a tensile strength of 30.1 ± 1.7 MPa, and an elongation at break of 891.7 ± 22.6%, which are approximately 4.1, 1.5, and 1.6 times those of the PUDA/CNT-3wt% composite without IR treatment, respectively. The composite also demonstrates multi-stimuli-responsive (thermal-, IR-, and electro-) self-healing, shape memory, and reprocessability due to the photothermal effect of CNTs and dynamic DA bonds. Moreover, the composite can be fabricated into a wearable strain sensor to detect real-time human motions. This work provides a facile strategy to synergistically enhance the functional and mechanical properties of CPCs, offering promising applications in flexible wearable devices and electromagnetic interference shielding.

Keywords: Self-reinforced segregated structure, Dynamic Diels-Alder cross-linking, Mechanical properties, Electrical conductivity, Multi-stimuli responsive shape memory, Self-healing