Assembling of Reprocessable Polybutadiene-Based Vitrimers with High Strength and Shape Memory via Catalyst-Free Imine-Coordinated Boroxine

TLDR

Vitrimers confer malleability and reprocessability to cross‑linked polymers through exchange reactions, yet achieving high‑strength, shape‑memory materials without catalysts under mild conditions remains difficult. This work proposes a catalyst‑free, facile strategy to create a polybutadiene‑based network that incorporates exchangeable imine bonds and N‑coordinated boroxine to meet that challenge. The network is formed by reacting PB grafted with 2‑aminoethanethiol with the formyl group of phenylboronic acid, followed by dehydration at room temperature to generate a dual‑dynamic covalent cross‑link. The resulting dual‑dynamic network delivers malleability, a tensile strength of 12.35 MPa, reprocessability, thermal‑induced shape‑memory, and retains properties after multiple recycling cycles, while also enabling end‑of‑life rubber reuse.

Abstract

Vitrimers endow cross-linked polymers with malleability and reprocessability via exchange reactions. However, designing of reprocessable, shape-memory polymer materials with high strength via a catalyst-free method remains a challenge under mild conditions. Here, we propose a facile strategy to address this dilemma by introducing the exchangeable imine bond and N-coordinated boroxine into a polybutadiene (PB)-based network. Specifically, PB grafted with 2-aminoethanethiol is reacted with the formyl group of phenylboronic acid and dehydrated to form a dual-dynamic covalently cross-linked network at room temperature. The dynamic network draws on the advantage of imine (toughness) and N-coordinated boroxine (strength), making the PB-based materials exhibit favorable malleability, mechanical property, reprocessability, and thermal-induced shape-memory behavior. We can obtain customized high mechanical properties by tuning the cross-linking density, and the tensile strength reaches a high value (12.35 MPa) without fillers or any other additives. Meanwhile, the unique network framework makes the material recycle over several times without sacrificing its property. This work presents a facile and effective approach to achieve a multifunctional polymer with customized attributes. Besides, this strategy can recycle end-of-life rubber to alleviate environmental pollution and provide inspiration for fabricating targeted materials by uniting the dynamic covalent or noncovalent bonds.