In Situ Constructing High-Performance, Recyclable Thermally Conductive Adhesives with a Hyperbranched-Star Reversibly Cross-Linking Structure

Abstract

Thermally conductive adhesives have attracted considerable attention in recent years due to their dual functions in promoting interfacial bonding and thermal transfer. A great number of strategies have been explored for producing them. However, most of them are based on irreversible covalent cross-linking resins, which are difficult to be recycled. Herein, we demonstrate a strategy for in situ producing high-performance, recyclable thermal adhesives from common stocks with a reversibly cross-linkable hyperbranched-star copolymer, HBPE@PSF. The copolymer possesses a hyperbranched polyethylene core covalently bearing multiple polystyrene side chains with small amount of furan moieties, which can be synthesized from commercially available ethylene and styrene as the main monomers. As a stabilizer, the copolymer can effectively promote the exfoliation of hexagonal boron nitride (h-BN) in chloroform under sonication to render high-quality boron nanosheets (BNNSs). Moreover, some of the copolymer can be irreversibly adsorbed on the BNNS surface based on the noncovalent CH−π and π–π interactions. From the resultant nanofiller, BNNS/HBPE@PSF composite adhesives have been successfully prepared through an in situ solution cast process directly with the copolymer as the matrix. After the cross-linking via the Diels–Alder reaction, the resultant adhesives simultaneously exhibit excellent interfacial bonding, thermal transfer, and recyclability, despite their extremely low furan content, 0.30 mol %. This has been confirmed to originate from the unique chain structure of the copolymer, which can form a hyperbranched-star, reversibly cross-linking structure in the composite system. The composite adhesives obtained herein may find their important applications as thermal interface materials in the areas of various electronic products.