Facile synthesis of macroscopic bilayer gels by one-shot radical polymerization in phase-separated binary solvent systems
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An innovative methodology for testing and selecting greener solvents for varnishing paintings
Organic solvents remain needed for certain treatments in cultural heritage conservation and restoration, including the application of traditional and synthetic resin varnishes on paintings. This research describes a collaborative approach for selecting and testing alternative greener sustainable solvents for this purpose. With commonly used solvent xylene targeted for substitution, initial solvent suggestions were made employing the SUSSOL (sustainable solvent selection and substitution) software tool considering key physical properties of the solvents and specified safety, health and environment hazard boundaries. In parallel HSPiP (Hansen Solubility Parameters in Practice) software was employed after the experimental determination of Hansen solubility parameters and the solubility of selected resins. Fourteen alternative solutions were selected and prepared from commonly used resins for application testing on reference substrates (e.g., Leneta cards and prepared canvas test boards). This testing included (1) the assessment of essential working properties, paint film solvent sensitivity, drying and film formation, and (2) standard coating tests such as water resistance, gloss, and color measurements. Comparable reference resin solutions used as varnishes, prepared with xylene and other solvents, were simultaneously evaluated. First standardized solvent tests provided a practical assessment of the sensitivity of the paint films to the substitute and reference solvents. Varnishing tests were subsequently performed on two historical paintings in order to evaluate the working properties and esthetic qualities of the resin solutions. The novel varnish Regalrez 1094 in isoamyl acetate showed very good working properties and gave a good visual result on both paintings. The resin solution Paraloid B72 in anisole showed good visual results on both paintings, while demonstrating acceptable working properties. This study illustrated that good working properties, protective and visual film qualities could be achieved with varnishes based on typical resins in alternative solvents. Various alternative greener solvents and their mixtures can thereby be suggested for dissolving and applying these resins. The approach within this study acknowledges the individuality of an artwork, which guides the selection of the most appropriate resin solution.
Development of deformable and adhesive biocompatible polymer hydrogels by a simple one-pot method using ADIP as a cationic radical initiator
In this study, a highly viscoelastic, deformable, and adhesive hydrogel was synthesized by crosslinking a 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer hydrogel with a chemical crosslinker [N,N′-methylenebisacrylamide (MB)] using a cationic initiator, 2,2′-azobis-[2-(1,3-dimethyl-4,5-dihydro-1H-imidazol-3-ium-2-yl)]propane triflate (ADIP). The adhesive PMPC gel was tolerant to peeling during adhesion, and the adhesion energy of the hydrogel increased as the contact time with the adhesion target increased. Furthermore, the mechanism underlying the synthesis of deformable and adhesive hydrogels was determined by analyzing the polymerization behavior. The polymer synthesized with ADIP had a lower molecular weight than that synthesized with a conventional redox-type initiator, ammonium persulfate/N,N,N′,N′-tetramethylethylenediamine. Moreover, an analysis of the reactivity of various monomers and crosslinkers indicated low reactivity of the acrylamide-type crosslinker MB to methacrylate-type monomers; on this basis, the appropriate combination of monomers and crosslinkers for generating the target hydrogel was determined. The cytocompatibility of the prepared PMPC hydrogel was also confirmed. Thus, this study provides guidelines for the rational design of highly deformable, adhesive hydrogels with cytocompatibility.
![1-octene polymerization catalyzed by titanium and zirconium complexes supported by [PN] or [NPN] ligands](https://i2.wp.com/media.springernature.com/lw685/springer-static/image/art%3A10.1038%2Fs41428-025-01018-8/MediaObjects/41428_2025_1018_Fig1_HTML.png?w=1024&resize=1024,1024&ssl=1 "1-octene polymerization catalyzed by titanium and zirconium complexes supported by [PN] or [NPN] ligands")
1-octene polymerization catalyzed by titanium and zirconium complexes supported by [PN] or [NPN] ligands
Ligands in homogeneous complex polymerization catalysts are crucial not only for influencing polymerization activity but also for controlling the stereoselectivity of the resulting polymers. We designed ligands on the basis of the dibenzophosphole skeleton and investigated the structure and ethylene polymerization activity of titanium and zirconium complexes activated by dried modified methylaluminoxane. In this investigation, we selected 1-octene as an α-olefin monomer and polymerized it using five types of titanium and zirconium complexes. Then, we obtained information regarding the ligand structure, polymerization activity toward 1-octene, and tacticity control. The [NPN]-Zr complex, which exhibited the highest activity for ethylene polymerization, demonstrated negligible polymerization activity for 1-octene. Conversely, titanium and zirconium complexes with [PN] ligands as auxiliary ligands exhibited activity toward 1-octene, yielding isotactic-rich polyoctene.
Tough polymer gels reinforced by strain-induced crystallization
Recently, we reported that strain-induced crystallization (SIC) of the polymer chains occurs in homogeneous polymer gels, such as slide-ring gels and Tri-/Tetra-PEG gels, with sufficiently high polymer concentrations. SIC significantly improves the mechanical toughness of homogeneous gels. Polymer crystals form and dissolve immediately after the polymer gels are stretched and unstretched. The quick formation and dissolution of the strain-induced crystals leads to elastic mechanical responses with minimal hysteresis under cyclic stretching. Tough and elastic polymer gels have potential applications in biomedical materials (ex. artificial ligaments and tendons) and soft electric devices (ex. soft actuators and flexible batteries) under repeated deformation.
Coexistence and interplay of pseudomagnetism and flexoelectricity in few-layer rippled graphene
The mechanical strain has been widely exploited as an effective knob to induce various intriguing phenomena in two-dimensional materials, notably the emergence of pseudomagnetism and flexoelectricity. Here, using tight-binding model calculations supplemented with selective crosschecks within first-principles theory, we present the first demonstration of coexisting pseudo magnetism and flexoelectricity in both rippled graphene monolayer and bilayer and further reveal the interplay of the strain-induced phenomena. For a rippled monolayer, lattice distortion induces the emergence of a synchronously modulated pseudomagnetic field, which in turn breaks the charge neutrality of the sublattices, as manifested by the concomitant presence of in-plane flexoelectricity. For a rippled bilayer, pseudomagnetism substantially enhances in some regions of the bottom layer and disappears in the corresponding regions of the top layer due to pronounced interlayer coupling, or vice versa, accompanied by simultaneous in-plane and out-of-plane polarizations with opposite directions. Collectively, these findings offer new opportunities for developing graphene-based multiferroic devices.
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