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

Abstract

High-performance polymers (HPPs) have good thermal and mechanical properties even under harsh environments and are widely used in aerospace, microelectronics, automobile, and other fields. Traditional employed highly cross-linked HPPs tend to fail in their performance at high temperatures due to the structural defects, which remains a challenge in both scientific investigation and engineering applications for decades. Herein, we employed a cyclosiloxane hybrid polymer (CHP) to investigate a new design strategy to compensate for the structural defects in the highly cross-linked network, which avoids catastrophic failure at high temperatures. Hyperbranched o-carborane was synthesized and used to compensate for structural defects of CHP. The antioxidant ability and toughness of CHP were improved, and it had better mechanical properties over a wide temperature range. Moreover, the anchoring effect of hyperbranched o-carborane in the cyclosiloxane network was systematically investigated. The hyperbranched o-carborane cage could stabilize the CHP network under dynamic thermal stress through anchoring the dangling bonds, and the highly cross-linked network suppressed the disintegration of the o-carborane cage by anchoring boron atoms of the ocarborane cage. Furthermore, the structural evolution mechanism of the o-carborane cage with increasing temperature was proposed. This fundamental research provided new insights into the design of HPPs for harsh environments.

Main-Chain Carborane-Embedded Polyethylene

“…Carborane is a rigid icosahedral boron-cluster compound that possesses outstanding thermal and chemical stability, which makes it a novel class of heat-resistant blocks suitable for enhancing polymer heat resistance and thermal stability. , As shown in Figure , carboranes can be integrated into polymer structures as pendants either in side chains or within the main chain, which is facilitated by various carborane derivatives . The incorporation of carborane moieties into a polymer backbone is largely prevalent in conjugated polymers, − polyesters, , polyurethane, , polyamides, , polysilanes/polysiloxanes, , thermosets, , and others through step-growth polymerization . In terms of side-chain carborane-containing polymers, controlled radical polymerization often leads to atactic polymers with a noncrystalline nature. − Coordination copolymerization of carborane-functionalized alkene with cyclooctene or ethylene could yield polyethylene-like polymers with bulky carborane as pendants. − More detailed synthetic strategies of carborane-containing polymers have been comprehensively reviewed in the latest work by Rendina and Müllner .…”

Bio-based Low-k Polymers at High Frequency Derived from Anethole: Synthesis and the Relationship between the Structures and the Properties

“…High-performance polymers are well-known for their high thermostability, excellent mechanical toughness, and physical and chemical resistance. , Their attractive properties make them widely applicable in aeronautics, astronautics, automotive, and electronic/microelectronic industries. – Nevertheless, most commonly used high-performance polymers are produced from fossil-based feedstocks. As the concerns about the consumption of fossil fuels and environmental issues grow, preparation of high-performance polymers from biomass feedstocks has been of interest specially. , It is because biomass feedstocks have the fascinating advantages of renewability, abundance, and structural diversity.…”