Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE This conductive fiber has a synergistic soft-hard core-sheath structure with strong interfacial bonding. Pre-stretching aligns MWCNTs and polymer chains for a stable conductive network. It shows excellent cyclic stability over 10,000 cycles at 50% strain, a 700% sensing range and tunable sensitivity.

ABSTRACT
The development of wearable electronics demands stretchable conductive fibers with exceptional electromechanical stability and durability under cyclic deformation and washing. Although polyurethane (PU)/carbon nanotubes (CNT) composites show promise, their practical application is hindered by poor interfacial compatibility and conductive network instability. This work presents a synergistic strategy integrating rational material design and microstructural engineering: (1) A heterogeneous sheath-core architecture is constructed using mechanically tailored PUs. It comprises a rigid isophthalic dihydrazide (IPDH)-based PU sheath for mechanical robustness and 3,5-diaminobenzoic acid (DABA)-based PU core matrix. The benzamide groups in DABA promote enhanced π–π interactions with MWCNT, thereby facilitating their dispersion. (2) A pre-straining treatment primarily reduces core-layer defects, resulting in a denser conductive core structure. The obtained fibers are characterized by ultra-high cyclic stability, enduring 10,000 stretching cycles at 50% strain with minimal signal drift. They are capable of sensing over a 0%–700% strain range with tunable gauge factors from 5.39 to 2041.71. Moreover, the fibers exhibit excellent washability, as their sensing performance remains stabilized after 30 washing cycles even with a slight decrease of conductivity. This study establishes a materials-structure–property relationship paradigm for next-generation durable stretchable conductors.