Heat Resistant Poly(carborane-siloxane) Adhesives

Organic adhesives have been extensively utilized in electronic manufacturing, automotive assembly, and household applications owing to their ease of processing, lightweight nature, and robust adhesion. However, organic chain oxidation and degradation under high temperatures induced catastrophic material failure in harsh environments like aerospace systems. To overcome this limitation, a series of vinyl-functionalized poly(carborane-siloxane) (PCS-x%) is synthesized via a one-pot method, subsequently crosslinked with 0.9 wt.% 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane to fabricate high-temperature adhesives (c-PCS-x%). The crosslinking density of the c-PCS-x% is modulated by adjusting the vinyl side group content in the PCS-x%. All c-PCS-x% demonstrated good thermal stability with less than 10% weight loss during degradation, particularly c-PCS-75% achieving the lowest weight loss of 3.6%. Thermal stabilization mechanisms are attributed to the crosslinked networks' suppressed borane fragment volatilization through covalent bonding and enhance cohesive energy by increased cross-linking density. The crosslinked c-PCS-x% adhesives surpass the linear analog (c-PCS-0%) in adhesion strength across temperatures ranging from room temperature to 250 °C. Notably, c-PCS-25% maintain 5.68 MPa adhesion strength post-aging at 200 °C/24 h and endure an ablation test for 10 min while sustaining a 1 kg load. This work establishes a novel molecular design for harsh environment adhesives through topology-controlled poly(carborane-siloxane) networks.