Hydrophobic, Pore‐Tunable Polyimide/Polyvinylidene Fluoride Composite Aerogels for Effective Airborne Particle Filtration

Abstract

Polyimide (PI) aerogels have great potential as filter materials, owing to their unique porous structure and excellent thermodynamic properties. In this work, polyvinylidene fluoride (PVDF) is introduced into the 3D network structure of crosslinked PI by phase separation to prepare PI/PVDF hybrid aerogels. By adding different amounts of PVDF, effective control of the aerogel porous structure is achieved, as a result, the air permeability of the hybrid aerogel is significantly improved while still achieving a filtration efficiency of airborne particulates of more than 99.8%. PVDF is aggregated and dispersed on the surface or inside of the aerogel in the form of nanoparticles, which effectively increases the hydrophobicity of the material. The contact angle of the prepared PI hybrid aerogel is ≈150°, and the water absorption is as low as 2.2%, which enables the aerogel to maintain structural stability in humid environments. In addition, the aerogel exhibits good adsorption effects on organic solvents.

Polyvinylidene Fluoride Aerogels with Tailorable Crystalline Phase Composition

“…However, the P12 and P9 samples have a higher specific surface area, 145 and 168 m 2 g −1 , respectively, in comparison with the prepared with ethanol of 113 and 136 m 2 g −1 for P12E0.2 and P9E0.2, respectively; these variations could be related to changes in the particles’ morphologies. In general, the obtained specific surface areas in this work are comparable with the ones reported in the literature of around 100 m 2 g −1 [ 16 , 32 , 52 ]; nevertheless, some authors reported PVDF–graphene composite aerogels with specific surface areas as high as 200 m 2 g −1 , which is attributed to the intrinsic graphene surface area [ 33 ].…”

“…Several synthetic approaches are focused on obtaining PVDF materials with a high content of the polar phases, including melting, mechanical stretching [ 12 , 13 , 14 ], annealing [ 15 , 16 ], blending [ 17 , 18 ], or addition of fillers [ 19 , 20 , 21 ], among others. However, such processing and fabrication techniques are impractical for certain materials, or they are not compatible with the final device design, thus stressing the importance of the exploration of alternative routes such as a precise crystal growth control [ 16 , 17 , 22 , 23 , 24 ]. Currently, different methods are being investigated to prepare PVDF materials such as fibers, films, or membranes exhibiting good piezoelectric properties; nonetheless, their performance is still far from alternative dense inorganic piezoelectric counterparts.…”

“…In this work, we tackled these challenges by developing a direct method to produce highly porous bulk PVDF aerogels with precise control of the phase composition, without further sample processing or the incorporation of a template. The limited available research on PVDF aerogels is focused on porous membranes [ 27 , 28 , 29 ], adsorbent media [ 30 , 31 , 32 ], composites [ 33 , 34 , 35 ], thermal insulation [ 36 ], and airborne particle filtration [ 16 , 37 ], mostly prepared by phase separation approaches using different solvents, followed by supercritical drying process, or in some cases by freeze drying, without meaningful attention on controlling the crystalline phases, somehow demonstrating that this porous system is seemingly ignored for piezoelectric applications. Consequently, an in-depth study on phase control has not been reported yet.…”

Novel, flexible, and transparent thin film polyimide aerogels with enhanced thermal insulation and high service temperature

“…The extreme hydrophobic nature of fluorocarbon resin can reduce the hydrophilicity of the PI aerogels. 117 Hybrid PI aerogels have also been investigated mainly by including polyvinylidene fluoride (PVDF) into the network, and WCAs of up to 1471 118 and 1521 119 have been reported. Apart from the aforementioned techniques, designing novel chemical backbones can also lead to hydrophobicity in PI aerogels.…”

Ultralight and Highly Resilient Boron Nitride Nanosheet/Polyimide Foams for Energy Harvesting and Sensing

“…The inherent characteristics of the fillers expand and improve the performance of the polymer foams, thus making their composite foams more extensive in application. These composite foams are widely used in electromagnetic shielding, 3 environmental protection, 4 sensors, 5 energy collection, 6 and so on. Most of these composites are mainly filled with 2D nanostructures.…”