Increasing emphasis in the rubber world on the production of environmentally friendly products has created a demand for alternative reinforcing fillers. Industrial lignin side-stream of lignocellulosic biomass has gained significant interest in this respect due to its abundancy and eco-friendly nature. In the present study, a recently developed, biobased hydrothermally treated (HTT) lignin was investigated as a potential functional filler for a solution styrene butadiene and butadiene rubber blend. Commercial reinforcing fillers N330 carbon black and ULTRASIL 7000 precipitated silica were used as references. Bis(triethoxy silylpropyl)tetrasulfide silane was used as a coupling agent for in situ surface compatibilization of this hydrothermally treated lignin with the hydrophobic rubber, as is commonly done for hydrophilic silica. The influence of unmodified and silane-modified lignin on the vulcanization, morphological, static and dynamic mechanical properties was investigated and examined with the reference fillers. The overall in-rubber properties exhibited by the silane-modified hydrothermally treated lignin are superior in comparison with those of the unmodified version. In comparison with reference fillers, this modified lignin shows semireinforcing behavior. The reinforcing properties are primarily due to networking of HTT lignin particles with rubber trapped-in or formation of sponge-like HTT lignin textures in the presence of silane, as observed with atomic force microscopy. The present work describes the complex reinforcement phenomena of using a silane as coupling agent for hydrothermally treated lignin and outlines its potential as an alternative rubber reinforcing filler.

Crosslinked anion-exchange membranes (AEMs) with reasonable water uptake are used for the separation of monovalent anions from their mixture with bivalent anions by electrodialysis (ED). Herein, we report the preparation of a series of monovalent-selective crosslinked AEMs containing imidazole rings from the polyacrylonitrile-co-poly(vinylimidazole) (PAN-co-PVIm) copolymer (AN/VIm ratio = 75:25 mol/mol), followed by N-alkylation with alkyl halide of different chain lengths (carbon number: 1,6,10,18), followed by reaction with 1,6-diamino hexane. The difference in the obtained permselectivity (PSO42–Cl–) was compared with those of un-crosslinked and commercial Ionsep membranes. The effects of crosslinking, the chain length of the alkyl spacer attached to imidazolium nitrogen of the membrane matrix, and the partial crystallinity occurring due to the arrangement of long alkyl chains on PSO42–Cl– were investigated. A representative crosslinked membrane (MQ18) with an octadecyl alkyl chain length (C18) attached to the imidazole moiety exhibited moderate water uptake (22%), high fixed charge density (0.037 meq/cm3), and high PSO42–Cl– (6.4) during the separation of a mixture of 0.01 M sodium chloride and 0.01 M sodium sulfate (2000 mg/L) by the ED process. The PSO42–Cl– value is further increased from 6.4 to 16.7 by increasing the electrolyte concentration to 0.05 M sodium chloride and 0.05 M sodium sulfate. The rigid imidazolium structure, locally organized higher chain length of the alkylating group, and the crosslinked network structure provide steric hindrance for the passage of more hydrophilic sulfate anions, which facilitates higher selectivity.

Rapid reversible phase transitions of biocompatible thermoresponsive sealants (TRS) upon cooling are required for their practical application in many sectors. The gel–sol transition rate of the TRS studied here [poly(N-isopropylacrylamide-co-butyl acrylate 95:5, number-averaged molecular weight = 7–64 kg mol–1] after being heated to 50 °C is slowed dramatically. The unheated materials return to a free-flowing sol form in a matter of minutes, while the heated materials remain in a gel or solid form for hours. The gel–sol transition of these polymers is enhanced in the presence of a high surface area host in the form of open-cell foams such as polyurethane (PUR), polyimide (PIM), hydrophilic polyurethane Aquazone (AQZ), and neoprene (NEO). An enhanced rate of sol formation on cooling and high TRS recovery (74–99%) were observed across a range of foam types and pore sizes when compared to samples stored without a host (9% recovery). Polyurethane demonstrates the greatest increase in TRS recovery (∼10-fold) after storing the TRS solution at 50 °C followed by cooling for 10 min at 0 °C, maintaining the thermally reversible gelation and mechanical strength of the TRS. Crucially, rheological measurements demonstrate that the viscosity, storage modulus, and loss modulus are not significantly affected by storage in a foam host. This work may be potentially extended to other injectable in situ forming hydrogels, which have suitable mechanical strength but less ideal phase transition times.

The use of electrospun bipolar membranes (BPMs) with an interfacial three-dimensional (3D) junction of entangled nano-/microfibers has been recently proposed as a promising fabrication strategy to develop high-performance BPMs. In these BPMs, the morphology and physical properties of the 3D junction are of utmost importance to maximize the membrane performance. However, a full understanding of the impact of the junction thickness on the membrane performance is still lacking. In this study, we have developed bipolar membranes with the same composition, only varying the 3D junction thicknesses, by regulating the electrospinning time used to deposit the nano-/microfibers at the junction. In total, four BPMs with 3D junction thicknesses of ∼4, 8, 17, and 35 μm were produced to examine the influence of the junction thickness on the membrane performance. Current–voltage curves for water dissociation of BPMs exhibited lower voltages for BPMs with thicker 3D junctions, as a result of a three-dimensional increase in the interfacial contact area between cation- and anion-exchange fibers and thus a larger water dissociation reaction area. Indeed, increasing the BPM thickness from 4 to 35 μm lowered the BPM water dissociation overpotential by 32%, with a current efficiency toward HCl/NaOH generation higher than 90%. Finally, comparing BPM performance during the water association operation revealed a substantial reduction in the voltage from levels of its supplied open circuit voltage (OCV), owing to excessive hydroxide ion (OH–) and proton (H+) leakage through the relevant layers. Overall, this work provides insights into the role of the junction thickness on electrospun BPM performance as a crucial step toward the development of membranes with optimal entangled junctions.

Due to the global environmental concerns caused by the ever-increasing environmental impact, landfill materials, and CO2 emission, there is a critical need in the elaboration of sustainable composite materials. Advanced material composites used in the production of high-performance products to solve some of the most difficult engineering challenges are having a key role in decarbonization by their light weight, higher performance, and increasing durability. In this work, sustainable carbon fiber reinforced composites (CFRCs) have been engineered with an environmentally friendly epoxy resin derived from natural and renewable compounds employing an industrial feasible manufacturing protocol. The thermosetting resin with a biobased organic carbon content (BOC) of ∼77% was synthesized by combining a renewable based monomer, the triglycidyl ether of phloroglucinol (TGPh), with hexahydro-4-methylphthalic anhydride (HMPA). The developed CFRCs show high performance with high glass transitions Tg > 350 °C, a high storage modulus ∼42 GPa, a high interlaminar shear strength ∼63 MPa, and a compressive strength ∼400 MPa. In addition, the outgassing tests show that both the resin and the CFRCs are compliant for space application. Moreover, the biobased CFRCs exhibit chemical recyclability, reprocessability, and excellent intrinsic flame resistance.

Conventional epoxy resins derived from unsustainable petroleum resources are unrecyclable and nondegradable. Herein, we facilely synthesized biobased vinylogous urethane epoxy thermosets (VUEs) using sustainable isosorbide and vanillic acid via a post-crosslinking method. Isosorbide was directly functionalized to isosorbide-bis-acetoacetate, which could be reacted with primary amines provided by triethylenetetramine and diamine to generate linear prepolymers with vinylogous urethane bonds. Then, VUEs were constructed, in which permanent covalent crosslinkers were generated by ring opening of the epoxy group in vanillin acid with the secondary amine already present in the linear prepolymer. By integrating different types of diamines, the obtained biobased VUEs display tunable mechanical properties; specifically, the tensile strength varies from 31.5 to 114.6 MPa and the elongation at break ranges from 9.5 to 150.0%. The VUE using ethylenediamine (TT-VUE) is comparable to that of bisphenol-A epoxy in terms of its mechanical qualities. The incorporation of vinylogous urethane bonds confers recyclable capability on VUEs, and the recycled VUEs show a lap shear strength of 7.39 MPa, indicating their potential application in adhesives. We envisaged that biobased VUEs with desirable tunable mechanical properties would be excellent replacements for petroleum-based epoxy resins.

Skin inflammation can occur due to the immune response of the body, infections, and injuries and lead to an increase of skin temperature. Cooling inflamed skin can relieve pain and efficiently dissipate heat. Evaporative cooling hydrogels are hence promising materials for preparing flexible dressings for cooling inflamed skin because of the high latent heat of water vaporization (∼2450 J·g–1 at 100 °C and 1 atm). We fabricate here a double-network hydrogel formed with poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and poly(N-isopropylacrylamide) (PNIPAM). Water can be released by the PNIPAM network above ∼32 °C, which is close to human’s skin temperature, and provides heat dissipation and cooling through evaporation. The network formed with PAMPS delays the release of water from the hydrogels. Large and prolonged cooling performance of a skin model and enhanced mechanical properties are obtained with the proposed design. Compared to other reported hydrogels for passive cooling, our material demonstrates a superior cooling power with lower temperature. This design of the hydrogel can be adapted for cooling other structures such as photovoltaic panels or roofs of buildings.

Recently, polymer materials with light-responsive shape memory and self-healing ability have been extensively studied. Various strategies have been reported to prepare remotely controllable light-responsive shape memory materials by employing carbon-based nanophotothermal agents (e.g., carbon nanotubes (CNTs)) in a shape memory polymer network. However, enhancing the dispersion state and capacity of CNTs remains a challenge for improving the response capability and rate of light-responsive shape memory materials. In this work, poly(vinyl alcohol) (PVA) modified with a pyrene groups was introduced as the polymer network, and CNTs were introduced as the nanophotothermal agent to prepare a light-responsive shape memory material with fast photothermal responsiveness. Because of the stacking interaction between pyrene and CNTs, a large fraction of CNTs are dispersed in an orderly way in the polymer matrix. Moreover, stacking and hydrogen bond interactions build up stable cross-links and endow the material with shape memory and self-healing ability. Therefore, this work provides an innovative strategy for preparing a shape memory material with an ultrafast photoresponse and self-healing performance.

Inclusion of dynamic covalent chemistries within polymer networks has been a topic of significant research due to the ability to endow these materials with reprocessability and recyclability; however, cleavage of dynamic bonds could also serve as a toughening mechanism in glassy thermosets. The influence on mechanical properties of including dynamic disulfide bonds within thermoset epoxies is investigated across broad temperatures and by utilizing several techniques including dynamic mechanical analysis, uniaxial tension and compression, microindentation, and fracture toughness testing. By analyzing the results in the context of a cohesive zone model, it was determined that the observed improvement in toughness in the disulfide-containing epoxies likely results from increased extensibility in the process zone due to preferential cleavage of disulfide linkages before macroscopic network failure. Observation of mechanochromic thiyl radicals in compression samples also provides evidence for increased plasticity in these dynamic glasses and suggests high strains are required for mechanical activation.

Long-term recurrent infections are one of the significant reasons why chronic diabetic wounds are difficult to heal, and the treatment of chronic wounds remains a major clinical challenge. In this work, we developed a kind of Janus hydrogel dressing capable of adjusting the complex microenvironment of wounds for promoting the healing of diabetic chronic wounds. The Janus hydrogel dressings are made of zwitterionic polymers and gentamicin sulfate-modified hyaluronic acid (HA-GS). One side of the hydrogel dressings was brushed with chitosan to act as a bridge between wound dressings and wound tissues. Thus, the wound dressings showed Janus properties with an antifouling surface on one side and an adhesive surface on the other, where the antifouling surface of zwitterionic hydrogels can avoid the adhesion of external bacteria, while the adhesive surface helps the dressings to be fixed on the wound. Moreover, the antibiotic GS was connected to HA through Schiff’s base, and thus it can be intelligently released in response to the acidic environment of infected wounds to kill the internal bacteria. The Janus hydrogel dressings were carefully characterized and investigated. In vivo results of a diabetic rat infected wound model showed that the Janus hydrogel dressings could effectively inhibit inflammation, accelerate the formation of granulation tissues and collagen deposition, and promote wound healing. Therefore, this multifunctional hydrogel dressing is a promising candidate for chronic wound healing in clinical practice.