Spider silk-inspired dynamic covalent polyurethane with fast repairing, shape memory, and strong dynamic adhesion via lignin enhanced microphase separation

Introducing microphase separation and dynamic bonds into the polymeric materials is an effective strategy to enhance the performance of polyurethane. Herein, a modified lignin-based polyol (MLOH) was developed via a facile one-step approach which greatly improved its reactivity and dispersibility compared to that of virgin lignin. Subsequently, inspired by the biphasic structure of natural spider silk, a high-performance modified lignin-based dynamic covalent polyurethane (MLPU) with lignin enhanced microphase separation was fabricated, exploiting the synthetic MLOH as the crosslinker and the dynamic oxime-carbamate bonds as the linkage. Besides possessing high repairing efficiency (3 min for 100%, 80 °C without pressure), and outstanding shape-memory capability, the optimized MLPU-2 demonstrated robust adhesive performance when applied as a polyurethane hot-melt adhesive, including a fast curing rate and high adhesive strength (10.50 MPa). Meanwhile, it also manifested remarkable solvent resistance, temperature tolerance from −30 °C to 60 °C, long-term durability for at least 3 months, on-demand debonding ability, and excellent reusability. The synergistic effect of lignin enhanced microphase separation and adjustable dynamic crosslinked structure endows the remarkable performance of this resultant dynamic covalent MLPU, which provides another way to develop green, sustainable polyurethane simultaneously with highly comprehensive performances for the potential practical application.