Copolymer Engineering of Elastic–Rigid Elastomers for Wash-Durable Conductive Pastes in Wearable Textile Electronics

Smart textiles require conductive materials that maintain electrical stability under repeated mechanical deformation and laundering while preserving textile-like flexibility. In this work, an elastic-rigid copolymer elastomer was designed as a polymer binder for washable conductive pastes used in wearable textile electronics. The copolymer was synthesized using polytetramethylene ether glycol (PTMEG), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), and m-xylylene diisocyanate (XDI), enabling the incorporation of thermally stable imide segments and elastic polyurethane domains within a single polymer framework. By adjusting the molar ratio between rigid and soft segments, the resulting copolymer exhibited balanced tensile strength, Young's modulus, and elastic recovery, outperforming a commercial thermoplastic polyurethane in mechanical performance. Silver-filled conductive pastes were prepared by dispersing 62 wt% micrometer-sized silver flakes into the copolymer matrix, achieving a bulk resistivity of 3.5 × 10^-5 Ω·cm. The printed conductive films showed stable electrical resistivity under cyclic tensile deformation up to 20% strain. Washing durability was further evaluated following the AATCC 135 top-loading laundering standard. After 50 laundering cycles, the resistance increase remained within 2.8-5.5 Ω for knitted fabrics and 2.0-5.1 Ω for woven fabrics, indicating satisfactory electrical stability and adhesion to textile substrates. These results suggest that elastic-rigid copolymer binders are suitable for the development of wash-durable conductive pastes for wearable textile applications.