Superflexible Multifunctional Polyvinylpolydimethylsiloxane‐Based Aerogels as Efficient Absorbents, Thermal Superinsulators, and Strain Sensors

Abstract

Aerogels are porous materials but show poor mechanical properties and limited functionality,whichsignificantly restrict their practical applications.P reparation of highly bendable and processable aerogels with multifunctionality remains ac hallenge.H erein we report unprecedented superflexible aerogels based on polyvinylpolydimethylsiloxane (PVPDMS) networks,P VPDMS/polyvinylpolymethylsiloxane (PVPMS) copolymer networks,a nd PVPDMS/PVPMS/ graphene nanocomposites by af acile radical polymerization/ hydrolytic polycondensation strategy and ambient pressure drying or freeze drying. The aerogels have ad oubly crosslinked organic-inorganic network structure consisting of flexible polydimethylsiloxanes and hydrocarbon chains with tunable cross-linking density,t unable pore sizea nd bulk density.T hey have ah igh hydrophobicity and superflexibility and combine selective absorption, efficient separation of oil and water,thermal superinsulation, and strain sensing.Materials for environmental protection, energy saving,and smart sensing are increasingly needed to meet the growing social demands for sustainable development. [1][2][3][4] Porous materials including aerogels, [5,6] macroporous monoliths, [7] hydrogels, [8] polymer and carbon foams, [9] supramolecular gels, [10] metal-organic frameworks (MOFs), [11] and periodic mesoporous materials [12] have drawn alot of interest for their wide range of applications,s uch as in thermal insulation, oil removal, energy storage,sensing,catalysis and drug delivery. In particular, much attention has been paid to aerogels owing to their unique properties,such as high porosity,high specific surface area (SSA), low density,a nd low thermal conductivity. [13][14][15] So far,m any kinds of aerogels based on silica, [16] metal oxide, [17,18] polymer, [19] carbon, [20] carbon nanotube, [21] and graphene [22] have been developed. However,t raditional aerogels are usually dried via costly supercritical drying (SCD) and exhibit low mechanical strength because of their intrinsically fragile/brittle networks,w hich need to be addressed before their practical applications.To overcome the costly drying process and brittleness, many efforts have been made to lower the cost by ambient pressure drying (APD), [23] freeze drying (FD) [22] and vacuum drying (VD), [24] and reinforce the aerogels by av ariety of methods.C ross-linking of aerogels with organic polymers is aw idely used method to reinforce the aerogels but usually results in lower porosity and higher density that limit their applications. [25,26] Flexible polymer-based aerogels can be obtained from resorcinol-formaldehyde, [27] poly(vinyl alcohol), [28] and supramolecules, [29] and some of them exhibit good absorption of organic solvents/oils.A nother kind of aerogels based on biomass such as nanocellulose and chitosan with compressibility and bendability have been reported. [30,31] Owing to their highly porous nanostructure that is composed of nanofibers,t hey show excellent thermal insulation performances.B esides,a ssembly of nanofibe...

The effect of graphene-nanoplatelets on gelation and structural integrity of a polyvinyltrimethoxysilane-based aerogel

“…A new class of aerogels called polymer-based silica aerogels has recently been created using polymerized precursors 6 with both nonparticulate (co-continuous) 7,8 and particulate [8][9][10] structure with different morphologies though the same range of properties. Zu et al [8][9][10] created series of transparent super-exible aerogels from a vinylmethyldimethoxysilane (VMDMS) or vinylmethyldiethoxysilane (VMDES) by radical polymerization followed by hydrolytic polycondensation resulting in a doubly crosslinked morphology. They showed low-density aerogels ($0.2 g cm À3 ) with exible hydrocarbon backbone chains, and elastic polymethylsiloxanes crosslinks leading to excellent superexibility in both bending and compression while maintaining the superinsulating properties ($l ¼ 15.2 mW m À1 K À1 ).…”

Elastic methyltrimethoxysilane based silica aerogels reinforced with polyvinylmethyldimethoxysilane

“…According to Zu's method, [23][24][25] we have successfully prepared PVMDMS polymers. The mixture of vinylmethyldimethoxysilane (VMDMS) and di-tert-butyl peroxide (DTBP) with a molar ratio of 10 : 1 was added to the hydrothermal reactor, and argon was injected into the hydrothermal reactor three times to remove air.…”

“…17 Thus, aerogels reinforced by these polymers usually exhibit heterogeneous core-shell structures, 1 which would be unfavorable to satisfy the requirements of silica aerogels with light weight, high surface area, and excellent insulation performance. Recently, Kanamori's group [23][24][25] has reported an innovative approach to prepare doubly cross-linked polyvinylpolydimethylsiloxane-based aerogels. This novel and facile preparation of the double-cross-linking structure is based on consecutive processes involving radical polymerization and hydrolytic polycondensation.…”

“…This novel and facile preparation of the double-cross-linking structure is based on consecutive processes involving radical polymerization and hydrolytic polycondensation. 25 In contrast to core-shell structures, the doubly cross-linked strategy is more conducive to forming homogeneous silica networks, avoiding obvious phase separation 23 and particles aggregation in the sol-gel process. Beneting from the organic bridge and homogeneous distribution of polyvinylmethyldimethoxysilane (PVMDMS) in silica networks, polyvinylpolydimethylsiloxane aerogels exhibit many merits, such as low density, uniform nanopores, high transparency, super compressibility, high bendability, excellent machinability, and thermal superinsulation.…”

False Morphology of Aerogels Caused by Gold Coating for SEM Imaging

“…Hence, structural elements, including variations in the geometry of the network forming entities down to the nanoscale, can be differentiated. These differences in fine structure are related to the chemical composition of the source material(s) and the conditions of gel syntheses [ 13 , 14 , 15 , 16 ]. The archetypes of aerogels (silica, cellulose, alginate, polyurea, etc.)…”