Although current technology related to transformation of carbon-carbon double bonds and ester groups of plant oils into hydroxyl groups have created variety of polyols for bio-based polyurethane, the resulting polyurethane always demonstrated poor mechanical properties and low glass transition temperature (T-g) due to lack of rigid units of these plant oil-based polyols. In this study, a strategy was proposed to utilize sucrose stearates with rigid pyran-furan ring and flexible side chains as plant-derived polyols which long-flexible fatty acids extracted from vegetable oils were bound to sucrose through ester bonds. These sucrose stearates could be directly used as Plant-derived polyols without any modification step for introducing hydroxyl groups on fatty acid chains applied by traditional technology in which the residual hydroxyl groups in the sucrose unit acted as the reactive sites for the following polymerization. A series of sucrose stearate-based polyurethanes were synthesized by reacting sucrose stearates with 1,6-diisocyanatohexane in a stoichiometric ratio. The resulting polyurethane membranes showed high transparency (>90 %, colorless), high friction resistance (7H), high water resistance, high glass transition temperature (105 degree celsius) and excellent mechanical performance due to synergistic effect of rigid main chains of sucrose and flexible side chains of stearates. This study reported a new strategy for bio-based polyols and high performance polyurethanes which could find potential applications as functional and renewable biomass-based coatings, membranes or plastics.

The low-temperature environment caused by solvent evaporation leads to the condensation of water vapor into water droplets that remain on the surface of the film to form breath figure patterns. The conventional approach to regulate the pore morphology in the breath figure process is to optimize the ambient temperature, humidity, and solution concentration. However, realizing a wide adjustable window of pore size and uniform distribution of the pore are still challenges. Here, inspired by the rainfall phenomenon, we proposed a simple and efficient method called the “raining boxing method” (RBM) for preparing porous films based on exogenously given water droplets as templates. The RBM broadened the adjustable window of pore size (0.6–225 μm in this work) and solved the inherent problem of radial reduction of pore size from the film center to the edge caused by the significant difference in low-temperature duration at different locations accompanying the solvent evaporation process. Furthermore, this method could realize multi-types porous films, including surface porous films, spongy porous films, and honeycomb porous films, and could be universally applied in the casting process of various polymer solutions.

The easy failure, poor environmental adaptability and unsatisfactory electrochemical performances of hydrogels hinder their applications as key components of flexible power supply devices (PSDs). Herein, a PAA-based hydrogel with extraordinary strength and environmental adaptability is designed via a ternary system, consisting of the tannin-modified MXene (TA@MXene), ZnCl2-cellulose and malic acid (MA) electrolyte. The TA@MXene and ZnCl2-cellulose promote the crosslinking of hydrogel via forming multi networks, endowing the hydrogel with 1.9 MPa tensile strength and 620% stretchability. Furthermore, the hydrogel has 38.4 mS·cm−1 conductivity, thanks to the effective ion transfer channels in the hydrogel. The MA electrolyte provides a stable pH environment via forming an acid ionization system; also, MA and the high-concentration ZnCl2 solution enhance their electrochemical performance at extreme environments. Three typical PSDs were assembled using the resultant hydrogel as electrolyte/electrode. The as-prepared supercapacitors display a high specific capacity (173.5 mAh·g−1), a superior energy density (208.2 Wh·kg−1) and outstanding capacity retention (92.1% after 5000 cycles); flexible batteries efficiently respond to strain signals, with 0.77 V open-circuit voltage (Voc); the as-assembled TENG has a 110 V Voc (100% stretching deformation). We present a design strategy for the construction of advanced hydrogels based a ternary system that will promote flexible PSDs towards practical use.

The energy-intensive and time-consuming process required for disassembling natural materials into nanoblocks are the major obstacles for the practical applications of biopolymer nanomaterials. Herein, a one-pot, energy-efficient and directional preparation method for gently exfoliating cellulose into nanosheets was achieved by surface modification assisted swelling process. The resulting cellulose nanosheets (CNSs) exhibited diameters ranging from 100 to 480 nm and thicknesses of approximately 5 nm, with a maximum yield of 97.9 %. This method could be widely applicable to common cellulose raw materials. Contrary to other nanocellulose reported previously, CNSs could be dried and stored in solid state, and re-dispersed in aqueous phase, thereby convenient for storage and transportation. Cellulose nanosheets films (CNSFs) obtained from CNSs showed high transparencies (>90 %) and excellent gas barrier properties, especially for the water vapor permeability of only 0.0072x10(-10) cm(3) cm cm(-2) s(-1) Pa-1, which were superior to other cellulose based films. In the simulation experiment of dry food packaging, CNSF10 possessed remarkable water vapor and oxygen blocking capabilities comparable to commercial cling films and met the practical requirements. The preparing process of CNSs reported here had the advantages including easy implementation, energy efficiency, and environmentally friendliness, and expanded possibilities for large-scale and widespread utilization of nanocellulose.

The development of a strong and tough conductive hydrogel capable of meeting the strict requirements of the electrode of a hydrogel-based triboelectric nanogenerator (H-TENG) remains an enormous challenge. Herein, a robust conductive polyvinyl alcohol (PVA) hydrogel is designed via a three-step method: (1) grafting with 3,4dihydroxy benzaldehyde, (2) metal complexation using ferric chloride (FeCl3) and (3) salting-out using sodium citrate. The hydrogel contains robust crystalline PVA domains and reversible/high-density non-covalent interactions, such as hydrogen bonding, 7C-7C interactions and Fe3+-catechol complexations. Benefiting from the crystalline domains, the hydrogel can resist external forces to the hydrogel network; meanwhile, the reversible/ high-density of non-covalent interactions can impart gradual and persistent energy dissipation during deformation. The hydrogel possesses multiple cross-linked networks, with 6.47 MPa tensile stress, 1000 % strain, 35.24 MJ/m3 toughness and 37.59 kJ/m2 fracture energy. Furthermore, the inter-connected porous hydrogel has an ideal structure for ionic-conducing channels. The hydrogel is assembled into an H-TENG, which can generate open circuit voltage of - 150 V, short-circuit current of - 3.0 mu A, with superb damage immunity. Subsequently, road traffic monitoring systems are innovatively developed and demonstrated by using the H-TENG. This study provides a novel strategy to prepare superiorly strong and tough hydrogels that can meet the high demand for HTENGs.

A"deep eutectic solvent-in-water" hydrogelwith a wide range of operating temperatures was prepared using theLs-Fe3+ dynamic redox system, showing great potentialas an electronic skin. Conductivehydrogels have become one of the hot topics in flexiblestrain sensors owing to excellent biocompatibility, attractive mechanicalflexibilities, and conductive properties. However, the time-consumingpreparation of hydrogels and their unsuitable properties limit theirapplication in low-temperature environment and high temperatures.Here, a new class of "deep eutectic solvent-in-water"hydrogels (DIWHs) is reported for the first time through a one-stepgelation process in situ without solvent displacement, fabricatedby combining a hydrogel with deep eutectic solvent (DES). The DIWHis constructed using a dynamic oxidation and coordination system composedof sodium lignosulfonate (Ls) and Fe3+. The effect of DESand the optimal mass ratio of water and DES on the hydrogel propertieswas synthetically investigated. The addition of DES not only shortensthe polymerization time to 8 s and enhances the mechanical propertiesof the hydrogel but also provides some unique properties. For example,the addition of DES gives the gels greater self-healing ability andantibacterial properties. When the mass ratio of water to DES was1:3, excellent antifreezing and antidrying properties were impartedto the gel, and the elasticity of the hydrogel was maintained evenat -80 & DEG;C or stored at 60 & DEG;C for 7 days. Furthermore,the hydrogel exhibited strong interfacial adhesion to natural andsynthetic materials (up to 60 kPa on glass) due to the presence ofLs with a catechol structure. In conclusion, this work stimulatesmore interest in the sustainable and high-value utilization of DESand fully demonstrates the advantages of this new easy-to-preparecoacervation gel for sensing.

A simple and facile method to prepare fully biobasedepoxy elastomerswith a high toughness is still a big challenge. In this study, a seriesof fully biobased epoxy elastomers were prepared by curing differentepoxidized plant oils with a biobased diamine Priamine 1074. The curingbehavior and catalytic process of these biobased epoxy elastomerswas systematically studied. The effects of the different numbers ofepoxy groups of these epoxidized plant oils and the equivalent ratiosof amine and epoxy groups on the performance (thermal stability, mechanicalproperties, etc.) of the epoxy elastomers were studied and discussed.Furthermore, the potential of these epoxy elastomers as wearable flexiblesensors was explored. It is found that ring opening polymerizationand ester aminolysis reaction between amine groups of diamines andester groups of epoxidized plant oils simultaneously occurred duringthe curing process. The properties, (thermal stability, thermophysicaland mechanical properties, etc.) of these epoxidized plant oils couldbe tailored by selecting epoxidized plant oils with different numbersof epoxy groups and controlling equivalent ratios of amine and epoxygroups. The maximum elongation at break of the epoxy elastomers couldreach up to 338.58%. After spray coating with Ag nanowires, theseepoxy resins demonstrated excellent detection of motion signals atvarious joints and other regions of the body. Combining with the resultsof not being cytotoxic to Caco-2 cells, the epoxy elastomers reportedin this study are expected to be applied in the field of wearableflexible sensors. Fully biobasedepoxy elastomers were prepared from differentplant oils for potential application as flexible strain sensors.

Multifunctional hydrogels, particularly with superior mechanical properties and using green/sustainable approaches, have attracted increasing attention because of their many applications and consistency with the green chemistry principle; unfortunately, their effective fabrication process is challenging. In this work, inspired by unique functions in plant-derived components, a multifunctional polyacrylic acid (PAA) hydrogel was innovatively developed using ZnCl2 and biomass-derived materials. Ingeniously, ZnCl2 has multiple functions, in combination with cellulose, lignin, and citric acid (CA), delivering intriguing properties to the hydrogel system. As a solvent system, the ZnCl2 solution has extraordinary H-bonding-donating ability, dissolving cellulose macromolecular chains; subsequently, solubilized cellulose as green reinforced-fillers are added to hydrogel, improving the strength properties, with compression strength of similar to 4.1 MPa, tensile strength of similar to 795.4 kPa, and elongation at break of similar to 620 %. The lignin-ZnCl2 catalysis system imparts a fast PAA gelation process, and the resultant hydrogel has strong/long-lasting/repeatable adhesive strength of 25.5 kPa (on Zn-carbon cloth) in 28 days. Additionally, ZnCl2 can form reversible ionic/electrostatic interactions with both lignin and CA, further improving the adhesive and mechanical properties. As anti-freezing agents, water-retaining agents and conducting medium, ZnCl2 also endows the hydrogel with desirable environmental compatibility and good conductivity (14.2 mS center dot cm(-1)). Furthermore, the presence of plant-based components endows the hydrogel with ultraviolet (UV) blocking, biocompatibility and antibacterial attribute. Significantly, the as-prepared hydrogels are suited for such diverse applications as flexible wearable strain sensors, bio-electrodes and zinc-ion hybrid capacitors (ZHCs), even can efficiently work at -65 degrees C. This study provides a new strategy of engineering multifunctional hydrogels using plant-based functional components, and these hydrogels show promising applications in many emerging areas including electronic skin sensors, health monitoring and energy storage devices.

In this study, cellulose composite films (CCFs) were fabricated through controllable dissolution and regeneration process of cellulose with the addition of polyvinyl alcohol (PVA). The competition of hydrogen bond site between cellulose and PVA led to partial dissolution of cellulose and maintained morphology of micron fibers with width range from 14.55 to 16.16 μm, which served as in-situ visible light scatterers. With this unique micron structure, the obtained CCF exhibited high transparency up to 90.5 % at 550 nm and ultrahigh haze up to 96 %. Interestingly, CCF could be used as hazy and flexible substrate, such as scattering lamp covers for indoor light management, anti-glare screen protectors and anti-reflection layers of solar cell devices. Among them, the efficiency of the solar cell device could be improved by 10.38 % with the help of a low-cost, excellent-performance CCF.

Two series of semi-interpenetrating network hydrogels (P(AAN-co-AAM)-SF and P(AA-co-AAM)-SF) were constructed through one-step blending of silk fibroin with sodium acrylate or acrylic acid followed by ultraviolet (UV)-initiated free-radical copolymerization. The resulting silk fibroin composite hydrogels exhibited excellent mechanical properties due to the semi-interpenetrating network hydrogel formed by sodium polyacrylate and silk fibroin. Specifically, the P(AAN-co-AAM)-SF hydrogel showed a high fracture stress of 1.01 MPa, an elongation at break of 2000%, a high compressive strength of 17 MPa, and could be compressed up to 200 cycles without damage. Compared with other silk fibroin hydrogels, this work was in a leading position in terms of mechanical properties and antidrying ability. In addition, silk fibroin-based hydrogels showed no cytotoxicity, certain UV-shielding ability, and were specifically poured into pig tracheal sections, indicating the potential for future use as biological materials.

Through a simple strategy of immersion in a mixed solution of water/ethylene glycol (EG)/lithium chloride (LiCl), self-healing carboxymethyl chitosan (CA) hydrogels, that is, CA/N-vinylpyrrolidone-EG-Li+ hydrogels (CEH) with an ultra-low-temperature freezing resistance below -70 °C were fabricated. The introduction of electrolyte ions and small-molecule polyol also made these hydrogels highly conductive (0.8 S m-1) and imparted antidrying property to them, showing stable and reversible sensitivity to finger-wrist bending as well as 150 cycles of stretching. Such hydrogels also presented highly efficient self-healing ability, with a stress-strain healing efficiency of over 90%. Furthermore, the CEH-based sensors maintained a stable sensing performance over a wide range of temperatures below the freezing point (from -10 to -70 °C) and exhibited stable sensitivity to temperatures with fast response and no significant hysteresis. The present work is expected to provide a simple and sustainable route for the preparation of multifunctional antifreezing conductive hydrogels based on CA, leading to a wide range of potential applications in soft sensor devices.

By a simple strategy of immersion in a CaCl2 solution, carboxymethyl chitosan hydrogels exhibited ultralowtemperature freezing resistance below -50 degrees C. In addition, the introduction of electrolyte ions endowed the hydrogels with electrical conductivity, showing stable and reversible sensitivity to human activity, such as finger bending, pressing, and pharyngeal swallowing. The conductive carboxymethyl chitosan hydrogels could even be assembled into a two-dimensional integrated array of contact sensors, which successfully perceived the contour and pressure distribution of an object with a certain resolution. These transparent biological-based antifreezing conductive hydrogels are promising to find applications in integrated wearable sensing devices under extremely low temperature environments.

On the basis of the original hydrogen bonding interaction and physical entanglement, covalent cross-linking and ionic cross-linking were additionally introduced to construct a carboxymethyl chitosan/allyl glycidyl ether conductive hydrogel (CCH) through a one pot method by a graft reaction, an addition reaction, and simple immersion, successively. The multiple cross-linking networks significantly increased the strength of CCHs and endowed them with ionic conductivity and an antifreezing property at -40 °C, which showed stable, durable, and reversible sensitivity to finger bending activity at subzero temperature. The CCHs could even be assembled into a triboelectric nanogenerator (TENG) to provide electric energy, which demonstrated stability against temperature variation, multiple drawing, long-term storage, or large quantities of contact-separation motion cycles. CCH-TENG can also be used as a tactile sensor within the pressure range from 0.4 kPa to higher than 8000 kPa. This work provided a simple route to fabricate antifreezing conductive hydrogels based on carboxymethyl chitosan and to find potential applications in soft sensor devices under a low temperature environment.

A dual physically crosslinking (DPC) strategy is used to construct hydrogels with ultrahigh strength. First, polyelectrolyte complex (PEC) hydrogels were prepared through in situ polymerization of acrylic acid monomers in chitosan solutions. Subsequently, cations and anions were introduced into the PEC hydrogels to form strong electrostatic interactions with the polymer chains. The mechanical properties of the DPC hydrogels strongly depended on the ionic concentration and the valence state of the loading ions. The tensile strength of DPC-Na 8-20-2.0, DPC-Mg 8-20-2.0, DPCAl 8-20-2.0 and DPC-Sul 8-20-0.8 reached to 2.36, 12.59, 65.1 and 2.80 MPa, respectively, which were significantly higher than that of PEC 8-20 (0.29 MPa). Moreover, DPC-Na, DPC-Mg and DPC-Sul still maintained a good flexibility. Speci fically, hydrogels of DPC-Ca exhibited ionic conductivity and freeze tolerance, which could be cooled to -20 degrees C without freezing. The DPC strategy opens an avenue to fabricate hydrogels with outstanding mechanical properties.