Chain Topology Design Enabling Efficient Polymer Reversible Cross-Linking for Self-Healing and Recyclable Adhesives

The development of high-performance, recyclable adhesives with self-healing ability is highly desirable for advanced electronic packaging. With this purpose, polymer reversible cross-linking has been intensively researched in recent years. Despite the progress, the existing strategies inevitably involve the use of some particular, reversibly cross-linkable components usually at high proportions, which limits their scalable applications. Herein, we demonstrate a strategy for achieving efficient polymer reversible cross-linking based on chain topology design. A set of hyperbranched star copolymers, HBPE@PSF, which mainly consist of ethylene and styrene units with a small amount of reversible cross-linkable component (FMA units, 0.30 to 0.80 mol %), were designed and synthesized. Then curing experiments on them were conducted under various controlled conditions to investigate their reversible cross-linking behavior. It has been testified that the resultant copolymers can form a thermally reversible cross-link structure via the DA reaction at efficiencies considerably higher than the linear analogues, PSF. This further imparts the HBPE@PSF with well-combined bonding, self-healing, and recyclable performances, although the copolymers contain a very low content of reversible cross-linkable components. By following this strategy, a series of reversible cross-linkable, hyperbranched star copolymers have been successfully synthesized from various different monomers, demonstrating its good universality. This research paves the way to produce high-performance, recyclable adhesives with various conventional monomers as the main raw stock.