Nitrogen-Coordinated borate esters induced entangled heterointerface toward multifunctional Silicone/Phenolic binary aerogel composites

Abstract

Organosilicone/phsenolic hybrid resin (SiR/PR), which can withstand thermal oxidation, is constantly plagued by significant phase separation during the co-curing process. Herein, coordination interaction between borate esters and siloxane was firstly proposed to achieve domain size below the visible wavelength (20 nm) and homogenous SiR/PBA-PR aerogels. Profiting from the electron-deficient boron element, the weak interactions of matrixes was compensated by nitrogen coordinated borate esters during the rapidly grafting process. The entangled heterointerface inherently endows the integrated “organic–inorganic” hybrid aerogels with hierarchical alveolate structure after oxidative decomposition. As expected, the distributed organosilicone, stabilized by nitrogen coordinated borate esters, shields the organic and carbonaceous components from ubiquitous oxygen-rich heat flow, thereby qualifying the SiR/PBA-PR aerogels with great thermal oxidation stability (R1000,Air > 50 wt%) and specific compressive strength (1400 N·m/kg). Besides, owing to the inherited heterointerface after pyrolysis, SET of pyrolytic sample with 50 % SiR even increase slightly (2.5 %) compared with the reduction of 73 % in SET of that without SiR after flame ablation. This strategy of silicone resin doping in nitrogen-coordinated phenolic resin will pave a way for “organic–inorganic” hybrid materials.