Conductive and Tough Smart Poly(N‐isopropylacrylamide) Hydrogels Hybridized by Green Deep Eutectic Solvent

Abstract

Conductive smart hydrogels with several virtues such as similar characters to biological tissues, sensitive response to ambient variations, have shown their excellent talents in the field of flexible electrical sensors, biomedical devices and directional transportation. However, complex preparing approaches or the instable inner structures have not only been time‐consuming, but also broken up the performance and reliability of the smart hydrogel‐based devices. In this work, a facile one‐step method is put forward to synthesize a kind of conductive poly(N‐isopropylacrylamide) (PNIPAM) hydrogel doped by a new green solvent of deep eutectic solvent (DES) containing choline chloride (ChCl) and acrylic acid (AA). Through the copolymerization of AA and NIPAM, the mechanical strength of the DES‐doped PNIPAM hydrogels is drastically improved compared to the pure PNIPAM gels, and some doped hydrogels lost the typical phase transition temperature of PNIPAM. Moreover, due to the ionic property of DES, the hybrid hydrogels also present the thermal‐depending conductivity as well as sensitive deformation response, which can be used as a smart switch in a circuit or a sensing element with environmental response ability. The cost‐effective preparation and the attractive performance of the DES‐doped hydrogels offer a new avenue to construct multi‐functional materials.

Self-Healing, Antibacterial, and 3D-Printable Polymerizable Deep Eutectic Solvents Derived from Tannic Acid

“…As far as we know, these results were clearly superior to other reported PDES materials, 22,28,29,43 which is mainly attributed to the incorporation of rigid TA molecules.…”

“…Glass transition temperature ( T g ) values were obtained from the peak values of tan δ curves. , When the content of TA grew from 10% to 40%, the E ′ at 25 °C ( E ′ 25 ) increased from 492 to 1828 MPa, and the T g values increased from 56.1 to 78.7 °C. As far as we know, these results were clearly superior to other reported PDES materials, ,,, which is mainly attributed to the incorporation of rigid TA molecules.…”

Poly(N-isopropylacrylamide)-Based Hydrogels for Biomedical Applications: A Review of the State-of-the-Art

“…Electrically conductive hydrogels exhibit flexibility (arising from hydrogel) and electrical conductivity (arising from conductive components) [ 282 ]. Further, electrically conductive hydrogels are divided into polymer-based (PPY, PANI, and PT) [ 283 , 284 , 285 , 286 , 287 ], metal-based (silver nanowires and gold nanoparticles) c [ 286 , 288 , 289 , 290 ], ionic (lithium chloride and sulfonate) [ 291 , 292 , 293 ], and carbon materials based (carbon nanotubes and graphene) [ 290 , 294 , 295 , 296 ]. Polypyrrole (PPy), being a conducting polymer, is extensively studied as an electrochemical actuator.…”

Transforming nature into the next generation of bio-based flexible devices: New avenues using deep eutectic systems

“…47,48 The pioneering work with acrylic acid functioning as an HBD to form a DES monomer with ChCl able to produce poly(acrylic acid) by free-radical polymerization has triggered the development of a series of DES monomers made of acrylates. 29 Some examples are methacrylic acid, 30 acrylamide, 49 N-isopropylacrylamide, 50,51 and itaconic acid. 52 By adding multifunctional monomers (e.g., crosslinkers) and tuning the DES monomers structure (e.g., its alkyl chain length and pendant groups), 27,49,53,54 the polymer's mechanical properties can be tailored, from glassy materials to flexible and stretchable polymer composites that exhibit electrical conductivity in the range of 10 À3 to 3.2 mS cm À1 (see Table 1 and Figure 1).…”