Renewable tannic acid based self-healing polyurethane with dynamic phenol-carbamate network: Simultaneously showing robust mechanical properties, reprocessing ability and shape memory

Abstract

Using green and renewable bio-based resources to realize multifunctional polymers is highly desirable for developing the next generation of smart materials. Herein, a facile method was proposed to prepare the thermally induced dynamic phenol-carbamate cross-linked thermoset polyurethane with robust mechanical properties, self-healing, reprocessing, and shape memory. Owing to the introduction of tannic acid (TA) that could form phenol-carbamate networks with isocyanate groups, the prepared TA based polyurethane (TA-PU) showed enhanced thermal stability and improved mechanical properties. Meanwhile, high self-healing efficiency could also be obtained by adjusting and controlling the content of dynamic phenol-carbamate bonds incorporated in polyurethane main chains, which indicated a good balance between robust mechanical properties and high self-healing efficiency in our target polymer. Further reprocessing tests demonstrated that the networked TA-PU polymer could also be well recycled by hot-pressing and solution casting. In addition, benefiting from the reversible crystallizable switching segments, that capable of being triggered by heat energy (when temperature is higher than the melting temperature of the soft segment), and cross-linked net points, the prepared TA-PU film could quickly recover from temporary shape to permanent shape. This elaborate design provides a heuristic perspective for developing multifunctional smart polymers from bio-based resources.