Anchoring Effect of Hyperbranched Carborane in Highly Cross-Linked Cyclosiloxane Networks toward High-Performance Polymers

High-performance polymers (HPPs) have good thermal andmechanicalproperties even under harsh environments and are widely used in aerospace,microelectronics, automobile, and other fields. Traditional employedhighly cross-linked HPPs tend to fail in their performance at hightemperatures due to the structural defects, which remains a challengein both scientific investigation and engineering applications fordecades. Herein, we employed a cyclosiloxane hybrid polymer (CHP)to investigate a new design strategy to compensate for the structuraldefects in the highly cross-linked network, which avoids catastrophicfailure at high temperatures. Hyperbranched o-carboranewas synthesized and used to compensate for structural defects of CHP.The antioxidant ability and toughness of CHP were improved, and ithad better mechanical properties over a wide temperature range. Moreover,the anchoring effect of hyperbranched o-carboranein the cyclosiloxane network was systematically investigated. Thehyperbranched o-carborane cage could stabilize theCHP network under dynamic thermal stress through anchoring the danglingbonds, and the highly cross-linked network suppressed the disintegrationof the o-carborane cage by anchoring boron atomsof the o-carborane cage. Furthermore, the structuralevolution mechanism of the o-carborane cage withincreasing temperature was proposed. This fundamental research providednew insights into the design of HPPs for harsh environments.