Facile and Green Strategy for Designing Ultralight, Flexible, and Multifunctional PVA Nanofiber‐Based Aerogels

Abstract

significant attention. However, their practical application is seriously restricted by their poor flexibility and fragility, which result from inefficient structure continuity and the loose connections between the socalled "pearl necklace-like" strings of inorganic nanoparticles. [24] As an alternative to inorganic aerogels, an organic aerogel was produced from resorcinol formaldehyde in 1987. [25] This was followed by the production of various other polymer aerogels (polyimide, polyurethane, polybenzoxazine, polyurea, and polystyrene), which reportedly had excellent mechanical properties, ultralow density, favorable thermal insulation properties, and diverse molecular designs. The preparation of these polymer aerogels often starts with their monomers or precursors and is followed by a supercritical drying process, which involves a sophisticated, expensive, and time-consuming synthesis process. Moreover, the use of toxic organic solvents is often inevitable. Therefore, a simple, feasible, and environmentally friendly method of preparing advanced aerogels with satisfying mechanical property and multifunctionality from widely available low-cost raw materials remains desirable.Poly(vinyl alcohol) (PVA) is a widely available and inexpensive polymer that is an attractive material for the fabrication of aerogels because it is biocompatible, chemically stable, has excellent mechanical properties, and is nontoxic. [26,27] To date, a variety of aerogels based on PVA have been successfully fabricated. However, such PVA aerogels are usually prepared by freeze-drying a modified PVA solution directly, [28][29][30][31] which results in a higher aerogel density. Moreover, to improve their mechanical properties, crosslinking agents-such as glutaraldehyde, [32] melamine formaldehyde, [33] and divinyl sulfone, [34] which have recognized disadvantages including potential toxic effects-are commonly used in the fabrication of PVA-based aerogels. [27] This greatly hinders the quantification of aerogels and their practical application. Therefore, it is an important challenge to develop a simple, low-cost, nontoxic, and green route for PVA aerogel synthesis.In recent years, new aerogels based on polymer nanofibers have been developed. [35][36][37][38] The nanofibers serve as building blocks to form a chemically crosslinked and/or physically entangled 3D network, unlike the interconnected framework of colloidal particles in inorganic aerogels. [38,39] Nanofiberbased aerogels do not have "necks" in their skeletons. This Polymer nanofiber aerogels are highly flexible and elastic. However, their preparation in a simple, low-cost, and environmentally friendly manner remains challenging. Herein, a green strategy for preparing an ultralight poly(vinyl alcohol) (PVA) nanofiber aerogel by electrospinning and freezedrying is reported. A simple thermal crosslinking method is used to make a mechanically robust material that can withstand up to 1000 times its own weight, i.e., no toxic crosslinking agents or organic solvents are used in any part of ...

Superhydrophobic polyvinylidene fluoride/polyimide nanofiber composite aerogels for thermal insulation under extremely humid and hot environment

“…Hence, constructing nanofibers into 3D nanofiber aerogels may be an eminent strategy for achieving promising properties in a wide range of applications. At present, many polymers, such as polyacrylonitrile (PAN) [25], poly(vinyl alcohol) (PVA) [32] and polyamideimide (PAI) [33], have been electrospun into nanofibers for the manufacture of 3D nanofiber aerogels. For instance, polyimide (PI) nanofibers have recently been employed as building blocks and fabricated into nanofiber aerogels due to their excellent mechanical strength, flexibility, thermostability and solvent resistance [34,35].…”

Recent advances in novel aerogels through the hybrid aggregation of inorganic nanomaterials and polymeric fibers for thermal insulation

“…Zhu et al. [ 154 ] developed ultralight, flexible, and multifunctional PVA nanofiber‐based aerogels, providing ideal material for ultralight thermal clothing. It is worth noting that there are some international manufacturers of aerogel clothing, such as Oros, Supild, and so on, which mainly provide gloves, jackets, coats, jackets, and snow pants for outdoor adventures.…”

Color tunable aerogels/sponge-like structures developed from fine fiber membranes

“…Notably, 3D porous structures like aerogels can be synthesized using nanoscale a Mechanical Engineering Department, University of Texas Rio Grande Valley, building blocks such as polymeric nanofibers; the resulting aerogels are highly elastic, flexible and environmentally friendly. 14 However, producing 3D scaffolds via the layer-by-layer deposition of luminescent nanofibers during electrospinning reduces the possibility to add desired scalable pores within the aerogels and they often exhibit mechanical instability. [15][16][17] Ding and Greiner independently initiated a facile strategy to produce ultralight nanofiber-based aerogels by wetting and cutting long electrospun fibers until a thorough dispersion of the fibers formed followed by freezing the solution and subsequently placing it in a freezedryer.…”