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

Thermally conductive adhesives have attracted considerableattentionin recent years due to their dual functions in promoting interfacialbonding and thermal transfer. A great number of strategies have beenexplored for producing them. However, most of them are based on irreversiblecovalent 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 reversiblycross-linkable hyperbranched-star copolymer, HBPE@PSF. The copolymerpossesses a hyperbranched polyethylene core covalently bearing multiplepolystyrene side chains with small amount of furan moieties, whichcan be synthesized from commercially available ethylene and styreneas the main monomers. As a stabilizer, the copolymer can effectivelypromote the exfoliation of hexagonal boron nitride (h-BN) in chloroform under sonication to render high-quality boronnanosheets (BNNSs). Moreover, some of the copolymer can be irreversiblyadsorbed on the BNNS surface based on the noncovalent CH-& pi;and & pi;-& pi; interactions. From the resultant nanofiller,BNNS/HBPE@PSF composite adhesives have been successfully preparedthrough an in situ solution cast process directly with the copolymeras the matrix. After the cross-linking via the Diels-Alderreaction, the resultant adhesives simultaneously exhibit excellentinterfacial bonding, thermal transfer, and recyclability, despitetheir extremely low furan content, 0.30 mol %. This has been confirmedto originate from the unique chain structure of the copolymer, whichcan form a hyperbranched-star, reversibly cross-linking structurein the composite system. The composite adhesives obtained herein mayfind their important applications as thermal interface materials inthe areas of various electronic products.