ACS Nano| high flexibility silicone aerogel as light as a feather for insulation
    Aerogels have many attractive properties but are usually costly and mechanically brittle, which always limit their practical applications. While many efforts have been made to reinforce the aerogels, most of the reinforcement efforts sacrifice the transparency or superinsulating properties. Here we report superflexible polyvinylpolymethylsiloxane, (CH2CH(Si(CH3)O2/2))n,aerogels that are facilely prepared from a single precursor vinylmethyldimethoxysilane or vinylmethyldiethoxysilane without organic cross-linkers. The method is based on consecutive processes involving radical polymerization and hydrolytic polycondensation, followed by ultralow-cost, highly scalable, ambient-pressure drying directly from alcohol as a drying medium without any modification or additional solvent exchange. The resulting aerogels and xerogels show a homogeneous, tunable, highly porous, doubly cross-linked nanostructure with the elastic polymethylsiloxane network cross-linked with flexible hydrocarbon chains. An outstanding combination of ultralow cost, high scalability, uniform pore size, high surface area, high transparency, high hydrophobicity, excellent machinability, superflexibility in compression, superflexibility in bending, and superinsulating properties has been achieved in a single aerogel or xerogel. This study represents a significant progress of porous materials and makes the practical applications of transparent flexible aerogelbased superinsulators realistic. The results are published in the latest issue of ACS Nano.
1. Preparation process

Figure 1. Synthesis route and resulting PVPMS aerogels and xerogels.

2. Surface morphology and wettability

Figure 2. Porous structure and mechanical properties of PVPMS aerogels.

Figure 3. Porous structure and mechanical properties of PVPMS xerogels.

3. Adsorption and leakage resistance

Figure 4. Drying process, structure, compression and bending cycle performances, and machinability.
    The aerogels and xerogels reported in this paper have low density combination (0.16-0.22 g cm-3), the pore size is homogeneous (most <60 nm), high specific surface area (900-1000 m2 g-1), high hydrophobicity (water contact angle > 130 degrees), and high transparency (> 80%), excellent machinability, super flexibility (withstanding 80% compression strain for 500 cycles), super elasticity (bending resistance for 100 cycles) and super insulation (λ = 15.0-15.4 mW m-1 K-1). The highly controllable double crosslinking method greatly enriches the preparation of porous materials and promotes the practical application of transparent high toughness aerogels in the field of super insulators.

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