Solid–Liquid–Vapor Triphase Gel

Abstract

Gels are soft functional materials with solid networks and open pores filled with solvents (for wet gels) or air (for aerogels), displaying broad applications in tissue engineering, catalysis, environmental remediation, energy storage, etc. However, currently known gels feature only a single (either solid–liquid or solid–vapor) interface, largely limiting their application territories. Therefore, it is both fundamentally intriguing and practically significant to develop conceptually new gel materials that possess solid–liquid–vapor multiple interfaces. Herein, we demonstrate a unique solid–liquid–vapor triphase gel, named as aerohydrogel, by gelling of a poly­(vinyl alcohol) aqueous solution with glutaraldehyde in the presence of superhydrophobic silica aerogel microparticles. Owing to its continuous solid, liquid, and vapor phases, the resultant aerohydrogel simultaneously displays solid–liquid, solid–vapor, and liquid–vapor interfaces, leading to excellent properties including tunable density (down to 0.43 g·cm–3), considerable hydrophobicity, and excellent elasticity (compressive ratio of up to 80%). As a proof-of-concept application, the aerohydrogel exhibits a higher evaporative cooling efficiency than its hydrogel counterpart and a better cooling capability than the commercial phase change cooling film, respectively, showing promising performance in cooling various devices. Moreover, the resulting aerohydrogel could be facilely tailored with specific (e.g., magnetic) properties for emerging applications such as solar steam generation. This work extends biphase gel (hydrogel or aerogel) to solid–liquid–vapor triphase gel, as well as provides a promising strategy for designing more aerohydrogels serving as soft functional materials for applications in various emerging fields.

Super‐Stretchable Hybrid Aerogels by Self‐Templating Strategy for Cross‐Media Thermal Management

“…The contact angles shown in Figure 2i indicate that the values increased with the increase of SSAP contents (82.1°, 99.1°, 121.3°, 123.1°and 142.5° corresponding to TPUA, TPUA‐5, TPUA‐10, TPUA‐15, and TPUA‐25, respectively), possibly due to the percentage of SSAPs been exposed on the surface of the thermoplastic polyurethane skeleton, as have been observed in our previous works. [ 26,48 ] The average thermal conductivities of the TPUA, TPUA‐5, TPUA‐10, TPUA‐15, and TPUA‐25 were 0.061, 0.057, 0.055, 0.055, and 0.052 W m −1 K −1 , respectively. The values were higher than that of typical silica aerogels but comparable to other porous materials such as graphene/MXene fiber aerogel, [ 49 ] possibly owing to the presence of macropores in the TPUAs.…”

Aerogel‐Functionalized Thermoplastic Polyurethane as Waterproof, Breathable Freestanding Films and Coatings for Passive Daytime Radiative Cooling

“…Thus, SSA must be physically dispersed and embedded in the TPU matrix. [ 47,48 ] The soft and hard segments of TPU caused microscopic phase separation, and the hard segments acted as physical crosslinkers in the elastic chain. However, owing to the low interfacial bonding between the SSA and TPU, the mutual aggregation of particles constituted to local defects.…”

Recent advances in flexible and soft gel-based pressure sensors

“…Gels are flexible and soft materials consisting of three-dimensional (3D) crosslinked polymer networks (solid content) and numerous internal open pores filled with either solvents (liquid content, e.g., hydrogels [30][31][32] and ionogels [33][34][35] ) or air (gas content, e.g., aerogels [36][37][38] ) [39][40][41] . Due to the framework of strong bonding between polymer chains and the redundant space of internal open pores for deformation, hydrogels and ionogels exhibit an intrinsic nature of superior flexibility and stretchability.…”

“…Physical crosslinking is based on the crosslinking of the polymer chains by non-covalent forces (i.e., secondary interactions), such as hydrogen bonding, ionic forces, van der Waals interactions, stereo complexation, polyelectrolyte complexation or hydrophobic forces [Figure 4A] [40,43] . Significantly, the polymer network should meet the following two conditions: (1) the interchain interaction must be strong to form a stable colligation in the molecular network; (2) the polymer network should encourage the access and residence of water [44] .…”

“…According to the polymer composition of gels, hydrogels can be divided into three types, i.e., natural hydrogels that mainly consist of DNA [92,93] , peptides [94,95] and polysaccharides [96,97] , synthetic hydrogels that mainly consist of polyacrylamide (PAAM), polyethylene glycol (PEG) [98] , PVA [99] , polyethylene oxide (PEO), poly(N-isopropylacrylamide) (PNIPAM) and poly(hydroxyethyl methacrylate) (PHEMA), and hybrid hydrogels [40] .…”