Surface-Initiated Metal-Free Photoinduced ATRP of 4-Vinylpyridine from SiO2 via Visible Light Photocatalysis for Self-Healing Hydrogels

Self-healing hyaluronic acid/polylysine hydrogel prepared by dual-click chemistry from polyrotaxane slidable crosslinkers

A new type of pH-sensitive hydrogel containing supramolecular structures was fabricated from maleimide-functionalized polyrotaxane, ɛ-polylysine and furan-functionalized hyaluronic acid by Diels-Alder reaction and amino-maleimide reaction. Firstly, pseudo polyrotaxane was obtained through self-assembly of polyethylene glycol and α-cyclodextrin, and then capped with 1-adamantanecarboxylic acid to convert it into polyrotaxane. Secondly, a maleimide-functionalized slidable crosslinker was obtained by modifying the polyrotaxane with 3-maleimide propionic acid, and furan-functionalized hyaluronic acid was prepared by modifying it with 2-furanmethylamine. Thirdly, the hydrogel cotaining supramolecular structures was fabricated from the prepared slidable crosslinker, ɛ-polylysine, and furan-functionalized hyaluronic acid in mixed solvent of water and N,N-dimethylformamide. Taking gel mass fraction and swelling ratio as two indicators, the formation parameters of hydrogel were optimized through single- factor experiments. The pH-sensitivity, rheological properties, self-healing performance, and degradation behavior of the hydrogel were investigated. Cytotoxicity assay, live/dead stains, and hemolysis assay were done to verify the biocompatibility of the hydrogel. Finally, the slow-release behavior of the hydrogel containing lidocaine hydrochloride was studied. The hydrogel possesses good biocompatibility, pH-sensitivity, self-healing behavior, degradation, and drug-controlled release, and can find broad application in biomaterials.

Toward Green Atom Transfer Radical Polymerization: Current Status and Future Challenges

Reversible-deactivation radical polymerizations (RDRPs) have revolutionized synthetic polymer chemistry. Nowadays, RDRPs facilitate design and preparation of materials with controlled architecture, composition, and functionality. Atom transfer radical polymerization (ATRP) has evolved beyond traditional polymer field, enabling synthesis of organic-inorganic hybrids, bioconjugates, advanced polymers for electronics, energy, and environmentally relevant polymeric materials for broad applications in various fields. This review focuses on the relation between ATRP technology and the 12 principles of green chemistry, which are paramount guidelines in sustainable research and implementation. The green features of ATRP are presented, discussing the environmental and/or health issues and the challenges that remain to be overcome. Key discoveries and recent developments in green ATRP are highlighted, while providing a perspective for future opportunities in this area.

Photoinduced Organocatalyzed Atom Transfer Radical Polymerization (O-ATRP): Precision Polymer Synthesis Using Organic Photoredox Catalysis

The development of photoinduced organocatalyzed atom transfer radical polymerization (O-ATRP) has received considerable attention since its introduction in 2014. Expanding on many of the advantages of traditional ATRP, O-ATRP allows well-defined polymers to be produced under mild reaction conditions using organic photoredox catalysts. As a result, O-ATRP has opened access to a range of sensitive applications where the use of a metal catalyst could be of concern, such as electronics, certain biological applications, and the polymerization of coordinating monomers. However, key limitations of this method remain and necessitate further investigation to continue the development of this field. As such, this review details the achievements made to-date as well as future research directions that will continue to expand the capabilities and application landscape of O-ATRP.

Metal-Free Organocatalyzed Atom Transfer Radical Polymerization: Synthesis, Applications, and Future Perspectives

Reversible deactivation radical polymerization (RDRP) is a class of powerful techniques capable of synthesizing polymers with a well-defined structure, properties, and functionalities. Among the available RDRPs, ATRP is the most investigated. However, the necessity of a metal catalyst represents a drawback and limits its use for some applications. O-ATRP emerged as an alternative to traditional ATRP that uses organic compounds that catalyze polymerization under light irradiation instead of metal. The friendly nature and the robustness of O-ATRP allow its use in the synthesis of tailorable advanced materials with unique properties. In this review, the fundamental aspects of the reductive and oxidative quenching mechanism of O-ATRP are provided, as well as insights into each component and its role in the reaction. Besides, the breakthrough recent studies that applied O-ATRP for the synthesis of functional materials are presented, which illustrate the significant potential and impact of this technique across diverse fields.

Recent Advances in the Synthesis of Polymer-Grafted Low-K and High-K Nanoparticles for Dielectric and Electronic Applications

The synthesis of polymer-grafted nanoparticles (PGNPs) or hairy nanoparticles (HNPs) by tethering of polymer chains to the surface of nanoparticles is an important technique to obtain nanostructured hybrid materials that have been widely used in the formulation of advanced polymer nanocomposites. Ceramic-based polymer nanocomposites integrate key attributes of polymer and ceramic nanomaterial to improve the dielectric properties such as breakdown strength, energy density and dielectric loss. This review describes the "grafting from" and "grafting to" approaches commonly adopted to graft polymer chains on NPs pertaining to nano-dielectrics. The article also covers various surface initiated controlled radical polymerization techniques, along with templated approaches for grafting of polymer chains onto SiO2, TiO2, BaTiO3, and Al2O3 nanomaterials. As a look towards applications, an outlook on high-performance polymer nanocomposite capacitors for the design of high energy density pulsed power thin-film capacitors is also presented.

In vitro study of alginate-gelatin scaffolds incorporated with silica NPs as injectable, biodegradable hydrogels

Porous substrates composed of biodegradable polymers and nanoparticles have found extensive use as three-dimensional (3D) scaffolds to regenerate damaged tissues through the incorporation of cells or growth factors. Here, injectable thermally responsive hydrogels based on SiO2 nanoparticles (NPs), alginate, and gelatin biopolymers, with possible utilization for cartilage tissue engineering, are introduced. The nanocomposites contain different amounts of SiO2 NPs for reinforcement and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) for chemical crosslinking of polymer chains in the 3D hydrogel network. The cross-sectional structure of the hydrogels containing 0.25, 1.5, and 3.0% SiO2 NPs was observed by FE-SEM, confirming porous morphology with interconnected pores. Based on the rheometer analyses, by increasing the amount of SiO2 NPs, the mechanical strength of the gels can be found. In addition, in vitro biodegradation studies show that the hydrogels without SiO2 are more unstable than the hydrogels containing SiO2 NPs. In vitro biocompatibility of the products tested by MTT assay indicates that cell viability and attachment depend on the presence of SiO2 NPs.

Advances in Synthesis and Applications of Self-Healing Hydrogels

BACKGROUND

Hydrogels, a type of three-dimensional (3-D) crosslinked network of polymers containing a high water concentration, have been receiving increasing attention in recent years. Self-healing hydrogels, which can return to their original structure and function after physical damage, are especially attractive. Some self-healable hydrogels have several kinds of properties such as injectability, adhesiveness, and conductivity, which enable them to be used in the manufacturing of drug/cell delivery vehicles, glues, electronic devices, and so on.

MAIN BODY

This review will focus on the synthesis and applications of self-healing hydrogels. Their repair mechanisms and potential applications in pharmaceutical, biomedical, and other areas will be introduced.

CONCLUSION

Self-healing hydrogels are used in various fields because of their ability to recover. The prospect of self-healing hydrogels is promising, and they may be further developed for various applications.

Structure-Directed Screening and Analysis of Thyroid-Disrupting Chemicals Targeting Transthyretin Based on Molecular Recognition and Chromatographic Separation

Exposure to thyroid-disrupting chemicals (TDCs) poses a great threat to human health. However, the screening and analysis of TDCs in environmental samples remain a tough work. In this study, we reported a structure-directed strategy for analyzing TDCs targeting transthyretin (TTR) based on molecular imprinting and chromatographic separation. The imprinted composites were prepared using l-thyroxine (T4) as a template and a tryptophan-like monomer screened from the amino acid library. The imprinted composites exhibited an adsorption capacity of 22.2 μmol g^-1 for T4 and an imprinting factor of 2.1. Chromatographic testing was then conducted among 72 chemicals using the imprinted composites-packed column. High retention factors were observed for chemicals that were structurally similar to T4. The chromatographic results were compared with a data set of 45 chemicals with known activities toward TTR. The results suggested that chemicals can be distinguished as TTR binders and nonbinders by retention factors, with a predictive accuracy of more than 90%. Moreover, the retention factors of chemicals were highly correlated with the reported relative potencies obtained from TTR assays. Thus, screening of TTR-binding chemicals can be realized through this simple chromatographic method. The imprinted composites were applied for target analysis and nontarget analysis of TTR-binding chemicals in dust samples. Three new TTR binders were successfully identified and verified by this method. The combination of molecular imprinting and chromatography opens up a new approach for screening TDCs targeting TTR.

Recent trends in nanopore polymer functionalization

Functional nanopores play an essential role in many biotechnological applications such as sensing, or drug delivery. Prominent examples are polymer functionalized ceramic or solid state nanopores. Intensive research efforts led to a discovery of a plethora of polymer functionalized nanopores demonstrating gated molecular transport upon basically all common stimuli. Nevertheless, nature's biological pore transport precision is unreached. This can be, among others, ascribed to limits in design precision especially with respect to functionalization. Recent trends in polymer functionalized nanopores address the role of confinement and polymerization control, strategies toward more sustainable reaction conditions, such as visible light initiation and strategies toward nanoscale local placement of polymer functionalization. The resulting multi-stimuli responsive nanopore performance enables concerted release or transport, side selective separation and selective detection.

PH-Sensitive, Polymer Functionalized, Nonporous Silica Nanoparticles for Quercetin Controlled Release

Some pH-sensitive, poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) grafted silica nanoparticles (SNPs) (SNPs-g-PDEAEMA) were designed and synthesized via surface initiated, metal-free, photoinduced atom transfer radical polymerization (ATRP). The structures of the polymers formed in solution were determined by 1H NMR. The modified nanoparticles were characterized by FT-IR spectroscopy, XPS, GPC, TEM and TGA. The analytical results show that α-bromoisobutyryl bromide (BIBB) (ATRP initiator) had been successfully anchored onto SNPs' surfaces, and was followed by surface-initiated, metal-free ATRP of 2-(diethylamino)ethyl methacrylate (DEAEMA). The resultant SNPs-g-PDEAEMA were uniform spherical nanoparticles with the particles size of about 22-25 nm, and the graft density of PDEAEMA on SNPs' surfaces obtained by TGA was 19.98 μmol/m2. Owing to the covalent grafting of pH-sensitive PDEAEMA, SNPs-g-PDEAEMA can dispersed well in acidic aqueous solution, but poorly in neutral and alkaline aqueous solutions, which is conducive to being employed as drug carriers to construct a pH-sensitive controlled drug delivery system. In vitro cytotoxicity evaluation results showed that the cytotoxicity of SNPs-g-PDEAEMA to the L929 cells had completely disappeared on the 3rd day. The loading of quercetin on SNPs-g-PDEAEMA was performed using adsorption process from ethanol solutions, and the dialysis release rate increased sharply when the pH value of phosphate-buffered saline (PBS) decreased from 7.4 to 5.5. All these results indicated that the pH-responsive microcapsules could serve as potential anti-cancer drug carriers.

Chitosan-grafted tetrapolymer using two monomers: pH-responsive high-performance removals of Cu(II), Cd(II), Pb(II), dichromate, and biphosphate and analyses of adsorbed microstructures

For circumventing the cumbersome and expensive multifunctional and multipolymer adsorbents for high-performance removals of hazardous water-contaminant(s), chitosan-g-[2-acrylamido-2-methyl-1-propanoic acid (AMPS)-co-2-(3-acrylamidopropanamido)-2-methylpropane-1-sulfonic acid (APAMPS)-co-2-(N-(3-amino-3-oxopropyl)acrylamido)-2-methylpropane-1-sulfonic acid (NAOPAMPS)-co-acrylamide (AM)] (i.e., chitosan-g-tetrapolymer), a multifunctional scalable and reusable hydrogel, was synthesized by grafting of chitosan and in situ attachments of N-H functionalized NAOPAMPS and APAMPS hydrophilic acrylamido-monomers during free-radical solution-polymerization of the two ex situ added AMPS and AM monomers in water. The response surface methodology was employed to synthesize one hydrogel envisaging the optimum balance between swelling and stability for the superadsorption of Cu(II), Cd(II), Pb(II), Cr₂O₇^2-, and HPO₄^2-. The in situ attachments of NAOPAMPS and APAMPS, grafting of chitosan into tetrapolymer, structures and properties, pH-responsive abilities, superadsorption mechanism, and reusability were understood via in depth microstructural analyses of adsorbed and/or unadsorbed chitosan-g-tetrapolymer(s) through ¹H/¹³C NMR, FTIR, XPS, TGA, XRD, DLS, and pH_PZC. The maximum adsorption capacities of Cd(II), Cu(II), Pb(II), Cr₂O₇^2-, and HPO₄^2- were 1374.41, 1521.08, 1554.08, 47.76, and 32.76 mg g^-1, respectively.

Surface Engineering of Porous Carbon for Self-Healing Nanocomposite Hydrogels by Mussel-Inspired Chemistry and PET-ATRP

In this work, surface-functionalized microcapsules from porous carbon nanospheres (PCNs) were successfully prepared by mussel-inspired chemistry with polydopamine (PDA) and metal-free photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP). These functional microcapsules are introduced into self-healing hydrogels to enhance their mechanical strength. The PCNs synthesized by a simple soft template method are mixed with linseed oil for loading of the biomass healing agent, and the microcapsules are first prepared by coating PDA. PDA coatings were used to immobilize the ATRP initiator for initiating 4-vinylpyridine on the surface of microcapsules by PET-ATRP. Using these functional microcapsules, the self-healing efficiency was about 92.5% after 4 h at ambient temperature and the healed tensile strength can be held at 2.5 MPa with a fracture strain of 625.2%. All results indicated that the surface-functionalized microcapsules for self-healing hydrogels have remarkable biocompatibility and mechanical properties.

Fabrication of Microcapsules by the Combination of Biomass Porous Carbon and Polydopamine for Dual Self-Healing Hydrogels

Artificial development of smart materials from agricultural waste or food residues is particularly desirable for green chemistry. In this paper, dual-network self-healing hydrogels were successfully fabricated by using functional microcapsules. These microcapsules were established by biomass porous carbon (PC) after recycling of apple residues. Glutaraldehyde (GA) as the healing agent was embedded in the porous carbon, and the outer surface was coated with polydopamine (PDA). After the microcapsules were added, modifying guar gum-type hydrogels were successfully obtained with dual self-healing performance by the combination of a healing agent and metal-ligand coordination. The self-healing efficiency was about 89.9% from the tension test, and the fracture strength was measured as 7.68 MPa. These results not only highlight a new idea for the utilization of apple residues but also provide a new method for the preparation of excellent self-healing hydrogels.

Self-healing and tough GO-supported hydrogels preparedviasurface-initiated ATRP and photocatalytic modification

Hydrogels with the properties of self-healing, toughness, stiffness and strength have great potential for use in smart materials.