Bio-Based Polyamide Fibers with Ultra-Toughness via Hierarchical Energy Dissipation Mechanisms

Abstract

Bio-based polymer materials have attracted growing attention in materials science research owing to their significant potential for advancing sustainable development and enabling green chemical engineering. Building upon the structural features of natural silk proteins, in this work, a long-chain bio-based polyamide (PA) with a nanocrystalline structure was developed using castor oil acid-derived monomers as raw materials. Copper(I) bromide was incorporated to establish cuprous–thioether metal coordination bonds with the thioether bonds in the PA main chain (PA3-Cu). Within this architecture, conventional hydrogen bonds served as primary energy-dissipating elements, whereas cuprous–thioether coordination bonds acted as secondary, sacrificial cross-links, significantly enhancing the mechanical properties. The metal-coordinated polyamide was melt-spun into elastic fibers, and the internal microstructure orientation was improved through stepwise cyclic stretching. The resulting Silk2 had a tensile strength of up to 416.8 MPa and an elastic recovery rate of over 90%, with a strength increase of approximately seven times compared to the unprestretched samples. The introduction of cuprous–thioether metal coordination bonds and the post-treatment of stepwise cyclic stretching can effectively enhance the mechanical properties of polyamide, providing a feasible strategy for preparing high-strength and high-toughness bio-based elastic fibers with controllable mechanical properties.