Versatile Double-Cross-Linking Approach to Transparent, Machinable, Supercompressible, Highly Bendable Aerogel Thermal Superinsulators

Abstract

A facile yet versatile approach to transparent, highly flexible, machinable, superinsulating organic-inorganic hybrid aerogels and xerogels is presented. This method involves radical polymerization of a single alkenylalkoxysilane to obtain polyalkenylalkoxysilane, and subsequent hydrolytic polycondensation to afford a homogeneous, doubly cross-linked nanostructure consisting of polysiloxanes and hydrocarbon polymer units. Here we demonstrate that novel aerogels based on polyvinylpolysilsesquioxane (PVPSQ), polyallylpolysilsesquioxane (PAPSQ), polyvinylpolymethylsiloxane (PVPMS), and polyallylpolymethylsiloxane (PAPMS) are facilely prepared via this approach from vinyltrimethoxysilane (VTMS, or vinyltriethoxysilane VTES), allyltrimethoxysilane (ATMS, or allyltriethoxysilane ATES), vinylmethyldimethoxysilane (VMDMS), and allylmethyldimethoxysilane (AMDMS), respectively. These aerogels combine low density, uniform nanopores, high transparency, super-compressibility, high bendability, excellent machinability, and thermal superinsulation (λ=14.5-16.4 mW m−1 K−1). More importantly, transparent, superflexible, superinsulating aerogel-like xerogels are obtained with PVPMS and PAPMS via highly scalable ambient pressure drying without any solvent exchange and modifications for the first time. This work will open a new way to transparent, highly flexible porous materials promising in the practical applications of thermal superinsulators, adsorbents, sensors, etc.