Ultrafast fabrication of deep eutectic solvent flexible ionic gel with high-transmittance, freeze-resistant and conductivity by frontal polymerization

Dual temperature/mechanical-responsive photonic crystal ionogels assembled by soft nanogels

In this paper, inspired by biological skin, photonic crystal ionogels with tuning stretching response and temperature response were cleverly constructed. By the method of emulsion precipitation polymerization, we firstly fabricated a series of nanogels composed of poly(N-isopropylacrylamide-co-N-(1-naphthyl) maleic acid) (P(NIPAM-co-NNMA)). The photonic crystals were constructed through the self-assembly of P(NIPAM-co-NNMA) nanogels in a mixing solvent of water and ionic liquid (IL) 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIM Otf). The phase transition temperature (Tp) of the nanogels was increased with an increase of the ionic liquid BMIM Otf in the mixing solvent. The photonic crystal ionogels (PIGs) were prepared by locking the photonic crystals via another polymer networks of poly (N,N-dimethylacrylamide) (PDMA). With decreasing ionic liquid, the structural color gradually becomes bright but the stretching strength and the elongation decreased. As the ratio of IL to water decreased to 2.9:1, the photonic crystal ionogels looked bright and the ionogels demonstrated a good elongation at break nearing 364%. As the ionogels were stretched, the structural color exhibited a blue-shift. Very interestingly, the structural color of the 100% stretching-ionogels was still stable as the content of PDMA was in a range of 15 wt% to 17 wt%. Furthermore, the composite device formed by integrating the temperature-responsive photonic crystal ionogels with carbon nanotubes (PIG-CNTs) films not only demonstrates electro-thermal conversion performance but also the ability to directly capture visual signals. This study provides a general and enlightening design strategy for the construction of high performance of photonic crystal ionogels.

Reactive amino acid-derived deep eutectic solvents for tailored lignin modification

The heterogeneous structure and characteristic variability of industrial lignin present key challenges that hinder its use in numerous advanced scenarios. Herein, we explore amino acid-derived deep eutectic solvents (AADESs) featuring diverse side chain structures (glycine, alanine, valine, lysine (Lys), and proline) and serving as reactive media for modifying alkali lignin. For the first time, quantum chemistry and molecular dynamics simulations were employed to demonstrate the formation mechanism of AADESs. Among all the considered systems, the Lys-based system proved to be the most stable system owing to its strong nucleophilicity. Unlike choline chloride-based DES, the strong nucleophilicity of Lys could induce nanocrystallization and targeted modification of α-OH to attach phenolic hydroxyl in lignin. Breaking the β-O-4 and β-β linkages within lignin increased the phenolic hydroxyl content of the lignin by up to ~50 %. Additionally, the -NH2 of amino acids can further increase the reactive sites of lignin, improve thermal stability, and facilitate further chemical modification. The reactivity of AADESs was notably influenced by the nucleophilicity of the side chains of amino acids, as also supported by the simulations. Overall, this research provides in-depth insights into lignin modification within sustainable and reactive solvents, advancing lignin valorization for high-end applications.

Fabrication of liquid-free ionic conductive elastomer (ICE) from cellulose-rosin derived poly(esterimide) towards temperature-tolerant and solvent-resistant UV shadowless adhesive and sensor

Recently, the utilization of the cellulose to fabricate the multifunctional materials with aim to replace the petroleum-based product, is receiving significant attentions. However, the development of cellulose-based multifunctional materials with high mechanical strength and temperature resistance is still a challenge. Herein, the intrinsic feature and property of cellulose and rosin were creatively employed to fabricate a novel cellulose-rosin based poly(esterimide) (PEI) by esterification reaction and imidization reaction, and the obtained cellulose-rosin derived PEI exhibits superior thermal stability. Then the as-prepared cellulose-rosin derived PEI was dissolved in polymerizable deep eutectic solvents (PDES) and in-situ formed the ionic conductive elastomer (ICE) with via UV-induced polymerization. These cellulose-rosin based ICE exhibited excellent mechanical properties, solvent resistance, and temperature tolerance. By adjusting the mass ratio of cellulose-rosin derived PEI and PDES, the as-prepared liquid-free ICE functions as UV shadowless adhesive and wearable sensors. The bonding strength of UV shadowless adhesive could 1.52 MPa, which could be applied to fix the broken glass toy models. Furthermore, wearable sensors based those ICE could monitor the large and subtle movements even under extreme environmental condition, such as being soaked in organic solvent (such as tetrahydrofuran) or at low/high temperature (-25 °C or 80 °C). This work opens a new avenue for the next-generation of multifunctional ICE.

Highly Transparent, Mechanically Robust, and Conductive Eutectogel Based on Oligoethylene Glycol and Deep Eutectic Solvent for Reliable Human Motions Sensing

Recently, eutectogels have emerged as ideal candidates for flexible wearable strain sensors. However, the development of eutectogels with robust mechanical strength, high stretchability, excellent transparency, and desirable conductivity remains a challenge. Herein, a covalently cross-linked eutectogel was prepared by exploiting the high solubility of oligoethylene glycol in a polymerizable deep eutectic solvent (DES) form of acrylic acid (AA) and choline chloride (ChCl). The resulting eutectogel exhibited high transparency (90%), robust mechanical strength (up to 1.5 MPa), high stretchability (up to 962%), and desirable ionic conductivity (up to 1.22 mS cm-1). The resistive strain sensor fabricated from the eutectogel exhibits desirable linear sensitivity (GF: 1.66), wide response range (1-200%), and reliable stability (over 1000 cycles), enabling accurate monitoring of human motions (fingers, wrists, and footsteps). We believe that our DES-based eutectogel has great potential for applications in wearable strain sensors with high sensitivity and reliability.

Cellulose-reinforced highly stretchable and adhesive eutectogels as efficient sensors

A cellulose-reinforced eutectogel was constructed by deep eutectic solvent (DES) and cotton linter cellulose. Cellulose was dispersed in the ternary DES consisting of acrylic acid, choline chloride and AlCl3·6H2O. The photoinitiator was then introduced into the system to in situ polymerize acrylic acid monomer to form transparent and ionic conductive eutectogels while keeping all the DES. The crosslinks formed by Al3+ induced ionic bonds and reversible links formed by hydrogen bonds give the eutectogels high stretchability (3200 ± 200 % tensile strain), self-adhesive (52.1 kPa to glass), self-healing and good mechanical strength (670 kPa). The eutectogels were assembled into sensors and epidermal patch electrodes that demonstrated high quality human motion sensing and physiological signal detection (electrocardiogram and electromyography). This work provides a facile way to design flexible electronics for sensing.