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.

Automated summary

Thermally conductive adhesives have been widely studied due to their dual functions in promoting interfacial bonding and thermal transfer. However, most existing strategies are based on non-recyclable irreversible covalent cross-linking resins. In this study, a strategy for in situ production of high-performance, recyclable thermal adhesives from common stocks using a reversibly cross-linkable hyperbranched-star copolymer, HBPE@PSF, was demonstrated. The copolymer, as a stabilizer, facilitated the exfoliation of hexagonal boron nitride (h-BN) to obtain high-quality boron nanosheets (BNNSs). The resultant composite adhesives, formed by combining BNNSs with the copolymer matrix through a solution cast process and cross-linking via the Diels-Alder reaction, showed excellent interfacial bonding, thermal transfer, and recyclability.