Progress and Perspectives Beyond Traditional RAFT Polymerization

Cucurbit[6]uril host-guest interaction assisted N-terminal epitope imprinted particles for cytochrome c recognition prepared by reversible addition-fragmentation chain transfer strategy

A novel strategy for cytochrome c selective recognition assisted with cucurbit[6]uril by host-guest interaction via N-terminal epitope imprinting and reversible addition-fragmentation chain transfer (RAFT) polymerization was developed. N-terminal nonapeptide of cytochrome c (GI-9) was used as the epitope template to achieve highly selective recognition of cytochrome c. As a common supramolecule in recent years, cucurbit[6]uril can encapsulate the butyrammonium group of lysine residue to capture the peptide and improve the corresponding spatial orientation by the host-guest interaction for GI-9 or cytochrome c recognition. After cucurbit[6]uril modification and epitope immobilization, the imprinted polymer was synthesized by RAFT polymerization with 2-dodecylsulfanylcarbothioylsulfanyl-2-methylpropanoic acid as chain transfer agent. After template removal, the obtained imprinted particles showed good binding ability to GI-9 (20.28 mg g-1, IF = 4.11) and cytochrome c (36.12 mg g-1, IF = 3.91). With the successive addition of cucurbit[6]uril and RAFT agent, the step-by-step improvement of the IF for cytochrome c recognition further illustrated the effects of supramolecular host-guest interaction and regulation of imprinted polymer chain. The imprinted polymers showed obvious advantages for cytochrome c recognition compared to competitive proteins and had good reusability with the repeated reproduction rate 80.8 % after five cycles of adsorption and desorption. Furthermore, the selective recognition for cytochrome c in adult bovine serum proved its potentiality to be applied in practical samples. All these results demonstrated that the combination of epitope imprinting, cucurbit[6]uril host-guest interaction and RAFT strategy presented an efficient new feasible control method for protein recognition with good selectivity, stability and reusability.

Biologically-driven RAFT polymerization-amplified platform for electrochemical detection of antibody drugs

The individualized administration and pharmacokinetics profiling are integral to the safe use of antibody drugs in immunotherapy. Here, we propose an electrochemical platform for the highly sensitive and selective detection of antibody drugs, taking advantage of the affinity capture by the peptide mimotopes together with the signal amplification by the biologically-driven RAFT polymerization (BDRP). Briefly, the BDRP-based platform involves the capture of antibody drugs by peptide mimotopes, the labeling of multiple reversible addition-fragmentation chain-transfer (RAFT) agents to the glycan chains of antibody drugs, and the BDRP-enabled controlled recruitment of numerous redox labels. The BDRP-based signal amplification relies on the reduction of RAFT agents by NADH coenzymes into the carbon-centered radicals, which can propagate efficiently into long polymer chains by reacting with the ferrocene-derivated monomers, recruiting numerous redox labels to the glycan chains of antibody drugs. The BDRP is conducted at the physiological temperature (i.e., 37 °C) and in the absence of external stimuli or radical sources, holding the advantages of biological compatibility and desirable simplicity over conventional RAFT polymerization approaches. The developed platform is highly selective and the detection limit in the presence of rituximab as the target was determined to be 0.14 ng/mL. Moreover, the applicability of the BDRP-based platform in the sensitive assay of antibody drugs in serum samples has been validated. In view of the biocompatibility, desirable simplicity, and cost-effectiveness, the BDRP-based platform shows great promise in the quantitative assay of antibody drugs.

Emergence of ADM-mediated bioconjugate to enhance longevity and catalytic efficiency of urease

The versatile nature of the urease enzyme makes it a valuable asset in biological and industrial contexts. The creation of bioconjugates using enzyme-polymer combinations has extended the shelf life and stability of urease. A triblock copolymer, PAM-co-PDPA-co-PMAA@urease (ADM@urease), was synthesized using acrylamide (AM), 2,5-dioxopyrrolidin-1-ylacrylate (DPA), methacrylic acid (MAA), and urease via the RAFT-Grafting-To polymerization method. This polymeric interface stabilizes the enzyme and enhances substrate binding and product release, significantly boosting enzymatic efficiency. To enhance pH's influence on urease activity, three ADM grades were developed by adjusting pH-responsive MAA levels, confirmed by GPC analysis. ADM micellized at acidic pH values of 6.47 or lower, with a critical micelle concentration (CMC) of at least 0.125 mg/mL. Kinetic evaluations using Berthelot reagents at various pH levels and temperatures compared free enzyme and urease encapsulated in ADM@urease. The Michaelis-Menten constant (Km) values, derived from the Lineweaver-Burk plot, were similar for both forms. The ADM@urease demonstrated optimal stability and catalytic efficacy with a Km value of 1.18 and Vmax of 1.92 at pH 4. By improving the stability, efficiency, and performance of urease, this encapsulation technology offers potential for sustainable, eco-friendly industrial applications and advancements in biotechnology.

Synthesis of Star Polymers with Ultrahigh Molecular Weights and Tunable Dispersities via Photoiniferter Polymerization

Simultaneous control over macromolecular chain topology, molecular weight, and dispersity is an important synthetic goal in polymer chemistry. The synthesis of well-defined poly(methyl acrylate) star polymers with ultrahigh molecular weights (>106 g mol-1) and tunable dispersities is realized for the first time via blue light-controlled photoiniferter polymerization using a tetrafunctional switchable RAFT agent (SRA4). The spectroscopic properties and polymerization activity of SRA4 can be reversibly tuned by addition of acid/base. For example, protonation of SRA4 with 4-toluenesulfonic acid (TsOH) leads to enhanced UV-visible light absorption, a faster polymerization rate, and a lower dispersity for the resulting star polymer. Star polymers were prepared with predicted molecular weights (Mn ≈ 80-1550 kg mol-1) and tunable dispersities (Đ ≈ 1.8-1.2) when targeting degrees of polymerization in the range of 1000-20000 in the presence of varying amounts of TsOH. High end-group fidelity for such star polymers was confirmed by one-pot chain extension experiments, which afforded a series of pseudoblock copolymers with controlled dispersities. Finally, rotational rheology was used to examine the effect of molecular weight, dispersity, and chain topology (whether linear or star-shaped) on solution viscosity.

Preparation of Polymerized High Internal Phase Emulsion Membranes with High Open-Cellular Extent and High Toughness via RAFT Polymerization

Porous polymer membranes with highly interconnected open-cellular structure and high toughness are crucial for various application fields. Polymerized high internal phase emulsions (polyHIPEs), which usually exist as monoliths, possess the advantages of high porosity and good connectivity. However, it is difficult to prepare membranes due to brittleness and easy pulverization. Copolymerizing acrylate soft monomers can effectively improve the toughness of polyHIPEs, but it is easy to cause emulsion instability and pore collapse. In this paper, stable HIPEs with a high content of butyl acrylate (41.7 mol% to 75 mol% based on monomers) can be obtained by using a composite emulsifier (30 wt.% based on monomers) consisting of Span80/DDBSS (9/2 in molar ratio) and adding 0.12 mol·L-1 CaCl2 according to aqueous phase concentration. On this basis, polyHIPE membranes with high open-cellular extent and high toughness are firstly prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. The addition of the RAFT agent significantly improves the mechanical properties of polyHIPE membranes without affecting open-cellular structure. The toughness of polyHIPE membranes prepared by RAFT polymerization is significantly enhanced compared with conventional free radical polymerization. When the molar ratio of butyl acrylate/styrene/divinylbenzene is 7/4/1, the polyHIPE membrane prepared by RAFT polymerization presents plastic deformation during the tensile test. The toughness modulus reaches 93.04 ± 12.28 kJ·m-3 while the open-cellular extent reaches 92.35%, and it also has excellent thermal stability.

Preparation of dual-epitopes imprinted particles with γ-cyclodextrin host-guest interaction and reversible addition-fragmentation chain transfer strategy for cytochrome c collaborative recognition

A dual-epitopes imprinted strategy for cytochrome c selective recognition assisted with γ-cyclodextrin host-guest interaction via N-terminal and C-terminal epitope's simultaneous imprinting and reversible addition-fragmentation chain transfer (RAFT) polymerization was developed. N-terminal and C-terminal nonapeptides of Cyt c (GI-9 and AE-9) were used simultaneously as the epitope to achieve collaborative recognition for cytochrome c. As a supramolecule, γ-cyclodextrin can encapsulate the aromatic functional groups of amino acid residues to capture the peptide and improve the corresponding spatial orientation for epitope or cytochrome c recognition by host-guest interaction. After the γ-cyclodextrin modification and dual-epitopes immobilization, the imprinted polymer was synthesized by RAFT polymerization with 4-cyano-4-(phenyl-carbonothioylthio) pentanoic acid as a chain transfer agent. After the template removal, the obtained dual-epitopes imprinted particles showed well binding ability to AE-9 (26.50 mg·g-1, IF= 4.13), GI-9 (7.36 mg·g-1, IF= 2.18) and cytochrome c (79.56 mg·g-1, IF= 3.27). With the successive addition of RAFT agent, the imprinting factor rising of epitope peptide and cytochrome c further illustrated the regulation of imprinted polymer chains. The imprinted particles had the advantage for cytochrome c recognition compared to other proteins and good reusability with 82.60 % repeated reproduction rate after six cycles of adsorption and desorption. Furthermore, the selective recognition for cytochrome c in bovine serum proved its potentiality to be applied in complex biological samples. It indicated that the combination of dual-templates epitope imprinting, γ-CD host-guest interaction and RAFT polymerization provided an efficient method for collaborative protein recognition with well selectivity, reusability and stability.

Reversible addition-fragmentation chain transfer enhanced aggregation signal-on fluorescence detection of alkaline phosphatase

The instability of the signal intensity of fluorescent biosensors and the false signals have been significant factors affecting the performance of biosensors. Herein, a novel signaling system is devised through the application of reversible addition-fragmentation chain transfer (RAFT) polymerization with monomers containing the tetraphenylethylene (TPE) groups. TPE exhibits an aggregation-induced emission (AIE) phenomenon in certain solvents, mainly due to the blockage of the rotation of its four benzene rings, which also exist in the aggregated state. With this property, a series of molecules are modified based on click chemistry for RAFT polymerization using Fe3O4 magnetic beads as the carriers, and stable aggregated luminescent TPE polymers are formed on the surface of magnetic beads to realize the transformation of fluorescence signal from "0" to "1". In addition, the fluorescence signal demonstrates a positive correlation with alkaline phosphatase (ALP) activity, which can be quantified by measuring the fluorescence intensity. The biosensor exhibits high sensitivity and good linearity in the range of 0.1-5 U/L, with a LOD of 0.079 U/L. Furthermore, the designed strategy demonstrated satisfactory performance in the quantitative determination of ALP activity in serum samples, indicating that the signaling system developed by combining RAFT polymerization and AIE molecules has an important application in the field of fluorescent biosensors.

Applications of Functional Polymeric Eutectogels

Over the past two decades, deep eutectic solvents (DESs) have captured significant attention as an emergent class of solvents that have unique properties and applications in differing fields of chemistry. One area where DES systems find utility is the design of polymeric gels, often referred to as "eutectogels," which can be prepared either using a DES to replace a traditional solvent, or where monomers form part of the DES themselves. Due to the extensive network of intramolecular interactions (e.g., hydrogen bonding) and ionic species that exist in DES systems, polymeric eutectogels often possess appealing material properties-high adhesive strength, tuneable viscosity, rapid polymerization kinetics, good conductivity, as well as high strength and flexibility. In addition, non-covalent crosslinking approaches are possible due to the inherent interactions that exist in these materials. This review considers several key applications of polymeric eutectogels, including organic electronics, wearable sensor technologies, 3D printing resins, adhesives, and a range of various biomedical applications. The design, synthesis, and properties of these eutectogels are discussed, in addition to the advantages of this synthetic approach in comparison to traditional gel design. Perspectives on the future directions of this field are also highlighted.

Electrochemically Generated Carbocations in Organic Synthesis

This Minireview examines a selection of case studies that showcase distinctive and enabling electrochemical approaches that have allowed for the generation and reaction of carbocation intermediates under mild conditions. Particular emphasis is placed on the progress that has been made in this area of organic synthesis and polymer chemistry over the past decade.

Functional Thermoplastic Polyurethane Elastomers with α, ω-Hydroxyl End-Functionalized Polyacrylates

Thermoplastic polyurethane (TPU) is an essential class of materials for demanding applications, from soft robotics and electronics to medical devices and batteries. However, traditional TPU development is primarily relied on specific soft segments, such as polyether, polyester, and polycarbonate polyols. Here, a novel method is introduced for developing TPU elastomers with enhanced performance and superior functionalities compared to conventional TPUs, achieved through the use of α,ω-hydroxyl end-functionalized polyacrylates. This approach involves a defect-free synthesis of α,ω-hydroxyl end-functionalized polyacrylates through visible-light-driven photoiniferter polymerization. By strategically blending these functionalized polyacrylates with conventional polyols, TPUs that exhibit exceptional toughness and notable self-healing capabilities, traits rarely found in existing TPUs are engineered. Furthermore, incorporating photo-crosslinkable acrylic monomers has enabled the creation of the first TPU with superior elastomeric properties and photopatterning capabilities. This approach paves the way for a new direction in polyurethane engineering, introducing a novel class of soft segments and unlocking the potential for a wide range of advanced applications.

Closed-loop recyclable polymers: from monomer and polymer design to the polymerization-depolymerization cycle

The extensive utilization of plastic, as a symbol of modern technological society, has consumed enormous amounts of finite and non-renewable fossil resources and produced huge amounts of plastic wastes in the land or ocean, and thus recycling and reuse of the plastic wastes have great ecological and economic benefits. Closed-loop recyclable polymers with inherent recyclability can be readily depolymerized into monomers with high selectivity and purity and repolymerized into polymers with the same performance. They are deemed to be the next generation of recyclable polymers and have captured great and increasing attention from academia and industry. Herein, we provide an overview of readily closed-loop recyclable polymers based on monomer and polymer design and no-other-reactant-involved reversible ring-opening and addition polymerization reactions. The state-of-the-art of circular polymers is separately summarized and discussed based on different monomers, including lactones, thiolactones, cyclic carbonates, hindered olefins, cycloolefins, thermally labile olefin comonomers, cyclic disulfides, cyclic (dithio) acetals, lactams, Diels-Alder addition monomers, Michael addition monomers, anhydride-secondary amide monomers, and cyclic anhydride-aldehyde monomers, and polymers with activatable end groups. The polymerization and depolymerization mechanisms are clearly disclosed, and the evolution of the monomer structure, the polymerization and depolymerization conditions, the corresponding polymerization yield, molecular weight, performance of the polymers, monomer recovery, and depolymerization equipment are also systematically summarized and discussed. Furthermore, the challenges and future prospects are also highlighted.

BaTiO3 Catalyzed Ultrasonic-Driven Piezoelectric-Induced Reversible Addition-Fragmentation Chain-Transfer Polymerization in Aqueous Media

Compared with normal stimulus such as light and heat, ultrasonic possesses much deeper penetration into tissues and organs and has lower scattering in heterogeneous systems as a noninvasive stimulus. Reversible addition-fragmentation chain-transfer polymerization (RAFT) in aqueous media is performed in a commercial ultrasonic wash bath with 40 kHz frequency ultrasonic, in the presence of piezoelectric tetragonal BaTiO3 (BTO) nanoparticles. Owing to the electron transfer from BTO under the ultrasonic action, the water can be decomposed to produce hydroxyl radical (HO•) and initiate the RAFT polymerization (piezo-RAFT). The piezo-RAFT polymerization exhibits features of controllable and livingness, such as linear increase of molar mass and narrow molar mass distributions (Mw/Mn < 1.20). Excellent temporal control of the polymerization and the chain fidelity of polymers are illustrated by "ON and OFF" experiment and chain extension, separately. Moreover, this ultrasonic-driven piezoelectric-induced RAFT polymerization in aqueous media can be directly used for the preparation of piezoelectric hydrogel which have potential application for stress sensor.

Harnessing Guanidinium and Imidazole Functional Groups: A Dual-Charged Polymer Strategy for Enhanced Gene Delivery

Histidine and arginine are two amino acids that exhibit beneficial properties for gene delivery. In particular, the imidazole group of histidine facilitates endosomal release, while the guanidinium group of arginine promotes cellular entry. Consequently, a dual-charged copolymer library based on these amino acids was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The content of the N-acryloyl-l-histidine (His) monomer was systematically increased, while maintaining consistent levels of methyl N-acryloyl-l-argininate hydrochloride (ArgOMe) or N-(4-guanidinobutyl)acrylamide hydrochloride (GBAm). The resulting polymers formed stable, nanosized polyplexes when complexed with nucleic acids. Remarkably, candidates with increased His content exhibited reduced cytotoxicity profiles and enhanced transfection efficiency, particularly retaining this performance level at lower pDNA concentrations. Furthermore, endosomal release studies revealed that increased His content improved endosomal release, while ArgOMe improved cellular entry. These findings underscore the potential of customized dual-charged copolymers and the synergistic effects of His and ArgOMe/GBAm in enhancing gene delivery.

Vitamin B3 Containing Polymers for Nanodelivery

Polymeric nanoparticles (NPs) with an integrated dual delivery system enable the controlled release of bioactive molecules and drugs, providing therapeutic advantages. Key design targets include high biocompatibility, cellular uptake, and encapsulating efficiency. In this study, a polymer library derived from niacin, also known as vitamin B3 is synthesized. The library comprises poly(2-(acryloyloxy)ethyl nicotinate) (PAEN), poly(2-acrylamidoethyl nicotinate) (PAAEN), and poly(N-(2-acrylamidoethyl)nicotinamide) (PAAENA), with varying hydrophilicity in the backbone and pendant group linker. All polymers are formulated, and those with increased hydrophobicity yield NPs with homogeneous spherical distribution and diameters below 150 nm, as confirmed by scanning electron microscopy and dynamic light scattering. Encapsulation studies utilizing a model drug, neutral lipid orange (NLO), reveal the influence of polymer backbone on encapsulation efficiency. Specifically, efficiencies of 46% and 96% are observed with acrylate and acrylamide backbones, respectively. Biological investigations showed that P(AEN) and P(AAEN) NPs are non-toxic up to 300 µg mL-1, exhibit superior cellular uptake, and boost cell metabolic activity. The latter is attributed to the cellular release of niacin, a precursor to nicotinamide adenine dinucleotide (NAD), a central coenzyme in metabolism. The results underline the potential of nutrient-derived polymers as pro-nutrient and drug-delivery materials.

Electroactive polymer tag modified nanosensors for enhanced intracellular ATP detection

ATP plays a crucial role in cell energy supply, so the quantification of intracellular ATP levels is particularly important for understanding many physio-pathological processes. The intracellular quantification of this non-electroactive molecule can be realized using aptamer-modified nanoelectrodes, but is hindered by the limited quantity of modification and electroactive tags on the nanosized electrodes. Herein, we developed a simple but effective electrochemical signal amplification strategy for intracellular ATP detection, which replaces the regular ATP aptamer-linked ferrocene monomer with a polymer, thus greatly magnifying the amounts of electrochemical reporters linked to one chain of the aptamer and enhancing the signals. This ferrocene polymer-ATP aptamer was further immobilized onto Au nanowire electrodes (SiC@C@Au NWEs) to achieve accurate quantification of intracellular ATP in single cells, presenting high electrochemical signal output and high specificity. This work not only provides a powerful tool for quantifying intracellular ATP but also offers a simple and versatile strategy for electrochemical signal amplification in the detection of broader non-electroactive molecules involved in different kinds of intracellular physiological processes.

An Evolutionary Review of Hemoperfusion Adsorbents: Materials, Preparation, Functionalization, and Outlook

Accumulation of pathogenic factors in the blood may cause irreversible damage and may even be life-threatening. Hemoperfusion is an effective technique for eliminating pathogenic factors, which is widely used in the treatment of various diseases including liver failure, renal failure, sepsis, and others. Hemoperfusion adsorbents are crucial in this process as they specifically bind and remove the target pathogenic factors. This review describes the development of hemoperfusion adsorbents, detailing the different properties exhibited by inorganic materials, organic polymers, and new materials. Advances in natural and synthetic polymers and novel materials manufacturing techniques have driven the expansion of hemoperfusion adsorbents in clinical applications. Stimuli-responsive (smart responsive) adsorbents with controllable molecular binding properties have many promising and environmentally friendly biomedical applications. Knowledge gaps, future research directions, and prospects for hemoperfusion adsorbents are discussed.

Robust Miniemulsion PhotoATRP Driven by Red and Near-Infrared Light

Photoinduced polymerization techniques have gathered significant attention due to their mild conditions, spatiotemporal control, and simple setup. In addition to homogeneous media, efforts have been made to implement photopolymerization in emulsions as a practical and greener process. However, previous photoinduced reversible deactivation radical polymerization (RDRP) in heterogeneous media has relied on short-wavelength lights, which have limited penetration depth, resulting in slow polymerization and relatively poor control. In this study, we demonstrate the first example of a highly efficient photoinduced miniemulsion ATRP in the open air driven by red or near-infrared (NIR) light. This was facilitated by the utilization of a water-soluble photocatalyst, methylene blue (MB+). Irradiation by red/NIR light allowed for efficient excitation of MB+ and subsequent photoreduction of the ATRP deactivator in the presence of water-soluble electron donors to initiate and mediate the polymerization process. The NIR light-driven miniemulsion photoATRP provided a successful synthesis of polymers with low dispersity (1.09 ≤ Đ ≤ 1.29) and quantitative conversion within an hour. This study further explored the impact of light penetration on polymerization kinetics in reactors of varying sizes and a large-scale reaction (250 mL), highlighting the advantages of longer-wavelength light, particularly NIR light, for large-scale polymerization in dispersed media owing to its superior penetration. This work opens new avenues for robust emulsion photopolymerization techniques, offering a greener and more practical approach with improved control and efficiency.

Modern Trends in Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) is a powerful and versatile technique for producing colloidal dispersions of block copolymer particles with desired morphologies. Currently, PISA can be carried out in various media, over a wide range of temperatures, and using different mechanisms. This method enables the production of biodegradable objects and particles with various functionalities and stimuli sensitivity. Consequently, PISA offers a broad spectrum of potential commercial applications. The aim of this review is to provide an overview of the current state of rational synthesis of block copolymer particles with diverse morphologies using various PISA techniques and mechanisms. The discussion begins with an examination of the main thermodynamic, kinetic, and structural aspects of block copolymer micellization, followed by an exploration of the key principles of PISA in the formation of gradient and block copolymers. The review also delves into the main mechanisms of PISA implementation and the principles governing particle morphology. Finally, the potential future developments in PISA are considered.

Nucleic Acid-Binding Dyes as Versatile Photocatalysts for Atom-Transfer Radical Polymerization

Nucleic acid-binding dyes (NuABDs) are fluorogenic probes that light up after binding to nucleic acids. Taking advantage of their fluorogenicity, NuABDs have been widely utilized in the fields of nanotechnology and biotechnology for diagnostic and analytical applications. We demonstrate the potential of NuABDs together with an appropriate nucleic acid scaffold as an intriguing photocatalyst for precisely controlled atom-transfer radical polymerization (ATRP). Additionally, we systematically investigated the thermodynamic and electrochemical properties of the dyes, providing insights into the mechanism that drives the photopolymerization. The versatility of the NuABD-based platform was also demonstrated through successful polymerizations using several NuABDs in conjunction with diverse nucleic acid scaffolds, such as G-quadruplex DNA or DNA nanoflowers. This study not only extends the horizons of controlled photopolymerization but also broadens opportunities for nucleic acid-based materials and technologies, including nucleic acid-polymer biohybrids and stimuli-responsive ATRP platforms.

Selective Electrochemical Modification and Degradation of Polymers

We demonstrate that electrochemical-induced decarboxylation enables reliable post-polymerization modification and degradation of polymers. Polymers containing N-(acryloxy)phthalimides were subjected to electrochemical decarboxylation under mild conditions, which led to the formation of transient alkyl radicals. By installing these redox-active units, we systematically modified the pendent groups and chain ends of polyacrylates. This approach enabled the production of poly(ethylene-co-methyl acrylate) and poly(propylene-co-methyl acrylate) copolymers, which are difficult to synthesize by direct polymerization. Spectroscopic and chromatographic techniques reveal these transformations are near-quantitative on several polymer systems. Electrochemical decarboxylation also enables the degradation of all-methacrylate poly(N-(methacryloxy)phthalimide-co-methyl methacrylate) copolymers with a degradation efficiency of >95 %. Chain cleavage is achieved through the decarboxylation of the N-hydroxyphthalimide ester and subsequent β-scission of the backbone radical. Electrochemistry is thus shown to be a powerful tool in selective polymer transformations and controlled macromolecular degradation.

Nanogels: Smart tools to enlarge the therapeutic window of gene therapy

Gene therapy can potentially treat a great number of diseases, from cancer to rare genetic disorders. Very recently, the development and emergency approval of nucleic acid-based COVID-19 vaccines confirmed its strength and versatility. However, gene therapy encounters limitations due to the lack of suitable carriers to vectorize therapeutic genetic material inside target cells. Nanogels are highly hydrated nano-size crosslinked polymeric networks that have been used in many biomedical applications, from drug delivery to tissue engineering and diagnostics. Due to their easy production, tunability, and swelling properties they have called the attention as promising vectors for gene delivery. In this review, nanogels are discussed as vectors for nucleic acid delivery aiming to enlarge gene therapy's therapeutic window. Recent works highlighting the optimization of inherent transfection efficiency and biocompatibility are reviewed here. The importance of the monomer choice, along with the internal structure, surface decoration, and responsive features are outlined for the different transfection modalities. The possible sources of toxicological endpoints in nanogels are analyzed, and the strategies to limit them are compared. Finally, perspectives are discussed to identify the remining challenges for the nanogels before their translation to the market as transfection agents.

Tuning the Mechanical Properties of 3D-printed Objects by the RAFT Process: From Chain-Growth to Step-Growth

Photoinduced 3D printing based on the reversible addition-fragmentation chain transfer (RAFT) process has emerged as a robust method for creating diverse functional materials. However, achieving precise control over the mechanical properties of these printed objects remains a critical challenge for practical application. Here, we demonstrated a RAFT step-growth polymerization of a bifunctional xanthate and bifunctional vinyl acetate. Additionally, we demonstrated photoinduced 3D printing through RAFT step-growth polymerization with a tetrafunctional xanthate and a bifunctional vinyl acetate. By adjusting the molar ratio of the components in the printing resins, we finely tuned the polymerization mechanism from step-growth to chain-growth. This adjustment resulted in a remarkable range of tunable Young's moduli, ranging from 7.6 MPa to 997.1 MPa. Moreover, post-functionalization and polymer welding of the printed objects with varying mechanical properties opens up a promising way to produce tailor-made materials with specific and tunable properties.

Functional nano drug delivery system with dual lubrication and immune escape for treating osteoarthritis

Local drug delivery via inter-articular injection offers a promising scenario to treat the most common joint disease, osteoarthritis (OA), which is closely associated with the increased friction or cartilage degeneration and the inflammatory syndrome of synovium. Therefore, it is quite necessary to improve the retention of drug delivery system within synovial joint, simultaneously restore the lubrication of degraded cartilage and meanwhile alleviate the inflammation. In this study, we propose a hydrophilic coating modified nano-liposome drug carrier (PMPC-Lipo) to achieve these functions. A modified chain transfer agent was utilized to polymerize 2-methacryloyloxyethyl phosphorylcholine (MPC), the obtained polymer, combined with lecithin and cholesterol, formed a liposome (PMPC-Lipo) where poly (MPC) acted as hydrophilic coating. PMPC-Lipo was found to restore the lubrication of mechanically damage cartilage (mimicking OA conditions) to the level like healthy cartilage due to the hydration lubrication. Additionally, due to the presence of poly (MPC), we also found PMPC-Lipo avoid the recognition of macrophage and thus escape from the phagocytosis to prolong its retention in synovial joint. Furthermore, after encapsulating gallic acid (GA) into PMPC-Lipo, the obtained GA-PMPC-Lipo can effectively scavenge reactive oxygen species and restore the imbalance of matrix secretion in inflammatory chondrocytes. Collectively, the proposed GA-PMPC-Lipo may provide a new idea for osteoarthritis treatment by providing both long-term effective drug action and excellent lubrication properties.

Poly(glycerol monomethacrylate)-encapsulated upconverting nanoparticles prepared by miniemulsion polymerization: morphology, chemical stability, antifouling properties and toxicity evaluation

In this report, upconverting NaYF4:Yb3+,Er3+ nanoparticles (UCNPs) were synthesized by high-temperature coprecipitation of lanthanide chlorides and encapsulated in poly(glycerol monomethacrylate) (PGMMA). The UCNP surface was first treated with hydrophobic penta(propylene glycol) methacrylate phosphate (SIPO) to improve colloidal stability and enable encapsulation by reversible addition-fragmentation chain transfer miniemulsion polymerization (RAFT) of glycidyl methacrylate (GMA) in water, followed by its hydrolysis. The resulting UCNP-containing PGMMA particles (UCNP@PGMMA), hundreds of nanometers in diameter, were thoroughly characterized by transmission (TEM) and scanning electron microscopy (SEM), dynamic light scattering (DLS), infrared (FTIR) and fluorescence emission spectroscopy, and thermogravimetric analysis (TGA) in terms of particle morphology, size, polydispersity, luminescence, and composition. The morphology, typically raspberry-like, depended on the GMA/UCNP weight ratio. Coating of the UCNPs with hydrophilic PGMMA provided the UCNPs with antifouling properties while enhancing chemical stability and reducing the cytotoxicity of neat UCNPs to a non-toxic level. In addition, it will allow the binding of molecules such as photosensitizers, thus expanding the possibilities for use in various biomedical applications.

5,12-Dihydroindolo[3,2-a]Carbazole Derivatives-Based Water Soluble Photoinitiators for 3D Antibacterial Hydrogels Preparation

Indolo[3,2-a]carbazole alkaloids have drawn a growing interest in recent years owing to their potential electrical and optical properties. With 5,12-dihydroindolo[3,2-a]carbazole serving as the scaffold, two novel carbazole derivatives are synthesized in this study. Both compounds are extremely soluble in water, with solubility surpassing 7% in weight. Intriguingly, the introduction of aromatic substituents contributed to drastically reduce the π-stacking ability of carbazole derivatives, while the presence of the sulfonic acid groups enables the resulting carbazoles remarkably soluble in water, allowing them to be used as especially efficient water-soluble PIs in conjunction with co-initiators, i.e., triethanolamine and the iodonium salt, respectively, employed as electron donor and acceptor. Surprisingly, multi-component photoinitiating systems based on these synthesized carbazole derivatives could be used for the in situ preparation of hydrogels containing silver nanoparticles via laser write procedure with a light emitting diode (LED)@405 nm as light source, and the produced hydrogels display antibacterial activity against Escherichia coli.

Visible Light Photoiniferter Polymerization for Dispersity Control in High Molecular Weight Polymers

The synthesis of polymers with high molecular weights, controlled sequence, and tunable dispersities remains a challenge. A simple and effective visible-light controlled photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization is reported here to realize this goal. Key to this strategy is the use of switchable RAFT agents (SRAs) to tune polymerization activities coupled with the inherent highly living nature of photoiniferter RAFT polymerization. The polymerization activities of SRAs were in situ adjusted by the addition of acid. In addition to a switchable chain-transfer coefficient, photolysis and polymerization kinetic studies revealed that neutral and protonated SRAs showed different photolysis and polymerization rates, which is unique to photoiniferter RAFT polymerization in terms of dispersity control. This strategy features no catalyst, no exogenous radical source, temporal regulation by visible light, and tunable dispersities in the unprecedented high molecular weight regime (up to 500 kg mol-1 ). Pentablock copolymers with three different dispersity combinations were also synthesized, highlighting that the highly living nature was maintained even for blocks with large dispersities. Tg was lowered for high-dispersity polymers of similar MWs due to the existence of more low-MW polymers. This strategy holds great potential for the synthesis of advanced materials with controlled molecular weight, dispersity and sequence.

Polymerization Induced Microphase Separation for the Fabrication of Nanostructured Materials

Polymerization induced microphase separation (PIMS) is a strategy used to develop unique nanostructures with highly useful morphologies through the microphase separation of emergent block copolymers during polymerization. In this process, nanostructures are formed with at least two chemically independent domains, where at least one domain is composed of a robust crosslinked polymer. Crucially, this synthetically simple method is readily used to develop nanostructured materials with the highly coveted co-continuous morphology, which can also be converted into mesoporous materials by selective etching of one domain. As PIMS exploits a block copolymer microphase separation mechanism, the size of each domain can be tightly controlled by modifying the size of block copolymer precursors, thus providing unparalleled control over nanostructure and resultant mesopore sizes. Since its inception 11 years ago, PIMS has been used to develop a vast inventory of advanced materials for an extensive range of applications including biomedical devices, ion exchange membranes, lithium-ion batteries, catalysis, 3D printing, and fluorescence-based sensors, among many others. In this review, we provide a comprehensive overview of the PIMS process, summarize latest developments in PIMS chemistry, and discuss its utility in a wide variety of relevant applications.

Cationic β-Scission of C-H and C-C Bonds for Selective Dimerization and Subsequent Sulfur-Free RAFT Polymerization of α-Methylstyrene and Isobutylene

A series of exo-olefin compounds ((CH3 )2 C(PhY)-CH2 C(=CH2 )PhY) were prepared by selective cationic dimerization of α-methylstyrene (αMS) derivatives (CH2 =C(CH3 )PhY) with p-toluenesulfonic acid (TsOH) via β-C-H scission. They were subsequently used as reversible chain transfer agents for sulfur-free cationic RAFT polymerization of αMS via β-C-C scission in the presence of Lewis acid catalysts such as SnCl4 . In particular, exo-olefin compounds with electron-donating substituents, such as a 4-MeO group (Y) on the aromatic ring, worked as efficient cationic RAFT agents for αMS to produce poly(αMS) with controlled molecular weights and exo-olefin terminals. Other exo-olefin compounds (R-CH2 C(=CH2 )(4-MeOPh)) with various R groups were prepared by different methods to examine the effects of R groups on the cationic RAFT polymerization. A sulfur-free cationic RAFT polymerization also proceeded for isobutylene (IB) with the exo-olefin αMS dimer ((CH3 )2 C(Ph)-CH2 C(=CH2 )Ph). Furthermore, telechelic poly(IB) with exo-olefins at both terminals was obtained with a bifunctional RAFT agent containing two exo-olefins. Finally, block copolymers of αMS and methyl methacrylate (MMA) were prepared via mechanistic transformation from cationic to radical RAFT polymerization using exo-olefin terminals containing 4-MeOPh groups as common sulfur-free RAFT groups for both cationic and radical polymerizations.

Size-Controlled Ammonium-Based Homopolymers as Broad-Spectrum Antibacterials

Ammonium group containing polymers possess inherent antimicrobial properties, effectively eliminating or preventing infections caused by harmful microorganisms. Here, homopolymers based on monomers containing ammonium groups were synthesized via Reversible Addition Fragmentation Chain Transfer Polymerization (RAFT) and evaluated as potential antibacterial agents. The antimicrobial activity was evaluated against Gram-positive (M. luteus and B. subtilis) and Gram-negative bacteria (E. coli and S. typhimurium). Three polymers, poly(diallyl dimethyl ammonium chloride), poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride), and poly(vinyl benzyl trimethylammonium chloride), were examined to explore the effect of molecular weight (10 kDa, 20 kDa, and 40 kDa) on their antimicrobial activity and toxicity to mammalian cells. The mechanisms of action of the polymers were investigated with dye-based assays, while Scanning Electron Microscopy (SEM) showed collapsed and fused bacterial morphologies due to the interactions between the polymers and components of the bacterial cell envelope, with some polymers proving to be bactericidal and others bacteriostatic, while being non-hemolytic. Among all the homopolymers, the most active, non-Gram-specific polymer was poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride), with a molecular weight of 40 kDa, with minimum inhibitory concentrations between 16 and 64 µg/mL, showing a bactericidal mode of action mediated by disruption of the cytoplasmic membrane. This homopolymer could be useful in biomedical applications such as surface dressings and in areas such as eye infections.

Visible Light-Accelerated Photoiniferter Polymerization in Ionic Liquid

The effect of ionic liquids on the reversible addition-fragmentation chain transfer (RAFT) polymerization mediated by a visible-light-induced photoiniferter mechanism was investigated. N,N-Dimethyl acrylamide was polymerized by photoiniferter polymerization in 1-ethyl-3-methylimidazolium ethylsulfate [EMIM][EtSO4] ionic liquid. We observed a considerable increase in the polymerization rate constants in ionic liquids (ILs), as well as in the mixed solvent of water and the IL, compared to those observed with water alone as the solvent. To demonstrate the robustness of the process, block copolymers with varying block ratios were synthesized with precise control over their molecular weight and mass dispersity (Đ). The very high chain-end fidelity provided by the photoiniferter polymerization in IL was described by using MALDI-ToF MS analysis.

Engineered Compounds to Control Ice Nucleation and Recrystallization

One of the greatest concerns in the subzero storage of cells, tissues, and organs is the ability to control the nucleation or recrystallization of ice. In nature, evidence of these processes, which aid in sustaining internal temperatures below the physiologic freezing point for extended periods of time, is apparent in freeze-avoidant and freeze-tolerant organisms. After decades of studying these proteins, we now have easily accessible compounds and materials capable of recapitulating the mechanisms seen in nature for biopreser-vation applications. The output from this burgeoning area of research can interact synergistically with other novel developments in the field of cryobiology, making it an opportune time for a review on this topic.

Multiblock copolymer synthesis via RAFT emulsion polymerization

A multiblock copolymer is a polymer of a specific structure that consists of multiple covalently linked segments, each comprising a different monomer type. The control of the monomer sequence has often been described as the "holy grail" of synthetic polymer chemistry, with the ultimate goal being synthetic access to polymers of a "perfect" structure, where each monomeric building block is placed at a desired position along the polymer chain. Given that polymer properties are intimately linked to the microstructure and monomer distribution along the constituent chains, it goes without saying that there exist seemingly endless opportunities in terms of fine-tuning the properties of such materials by careful consideration of the length of each block, the number and order of blocks, and the inclusion of monomers with specific functional groups. The area of multiblock copolymer synthesis remains relatively unexplored, in particular with regard to structure-property relationships, and there are currently significant opportunities for the design and synthesis of advanced materials. The present review focuses on the synthesis of multiblock copolymers via reversible addition-fragmentation chain transfer (RAFT) polymerization implemented as aqueous emulsion polymerization. RAFT emulsion polymerization offers intriguing opportunities not only for the advanced synthesis of multiblock copolymers, but also provides access to polymeric nanoparticles of specific morphologies. Precise multiblock copolymer synthesis coupled with self-assembly offers material morphology control on length scales ranging from a few nanometers to a micrometer. It is imperative that polymer chemists interact with physicists and material scientists to maximize the impact of these materials of the future.

The Role of Polymers in Halide Perovskite Resistive Switching Devices

Currently, halide perovskites (HPs) are gaining traction in multiple applications, such as photovoltaics and resistive switching (RS) devices. In RS devices, the high electrical conductivity, tunable bandgap, good stability, and low-cost synthesis and processing make HPs promising as active layers. Additionally, the use of polymers in improving the RS properties of lead (Pb) and Pb-free HP devices was described in several recent reports. Thus, this review explored the in-depth role of polymers in optimizing HP RS devices. In this review, the effect of polymers on the ON/OFF ratio, retention, and endurance properties was successfully investigated. The polymers were discovered to be commonly utilized as passivation layers, charge transfer enhancement, and composite materials. Hence, further HP RS improvement integrated with polymers revealed promising approaches to delivering efficient memory devices. Based on the review, detailed insights into the significance of polymers in producing high-performance RS device technology were effectively understood.

Advances in the Synthesis of Chemically Recyclable Polymers

The development of modern society is closely related to polymer materials. However, the accumulation of polymer materials and their evolution in the environment causes not only serious environmental problems, but also waste of resources. Although physical processing can be used to reuse polymers, the properties of the resulting polymers are significantly degraded. Chemically recyclable polymers, a type of polymer that degrades into monomers, can be an effective solution to the degradation of polymer properties caused by physical recycling of polymers. The ideal chemical recycling of polymers, i. e., quantitative conversion of the polymer to monomers at low energy consumption and repolymerization of the formed monomers into polymers with comparable properties to the original, is an attractive research goal. In recent years, significant progress has been made in the design of recyclable polymers, enabling the regulation of the "polymerization-depolymerization" equilibrium and closed-loop recycling under mild conditions. This review will focus on the following aspects of closed-loop recycling of poly(sulfur) esters, polycarbonates, polyacetals, polyolefins, and poly(disulfide) polymer, illustrate the challenges in this area, and provide an outlook on future directions.

Linear Cyclobutane-Containing Polymer Synthesis via [2 + 2] Photopolymerization in an Unconfined Environment under Visible Light

The [2 + 2] photopolymerization of diolefinic monomers is an appealing approach for the construction of polymeric materials. Herein, we demonstrate that the establishment of an effective donor-acceptor conjugation by introducing electron-donating alkoxy groups at appropriate positions of the benzene ring could activate p-phenylenediacrylate (PDA), thus enabling the development of the first solution [2 + 2] photopolymerization of such monomers under the irradiation of visible light. Variation on the alkoxy groups and the ester parts could allow access to a series of linear cyclobutane-containing polymer products with high molecular weight (up to 140 kDa) and good solubility in common solvents. Further, temporal control and postpolymerization modification with preinstalled pendant C═C bonds via thiol-ene click reaction are also demonstrated with this [2 + 2] photopolymerization system.

Synthesis and kinetic analysis of poly(N-acryloylmorpholine) brushes via surface initiated RAFT polymerization

Polymer brushes are promising many applications as smart materials and biocompatible surfaces. Surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the most effective techniques for synthesis of well-defined polymer brushes. Herein, a biocompatible, uniform and stable poly(N-acryloylmorpholine)-silicon hybrid system was achieved using surface-initiated RAFT polymerization. Evidence of a well-controlled surface-initiated RAFT polymerization was confirmed by a linear increase of number average molecular weight (Mn) with overall monomer conversions. Water contact angle, ellipsometry, X-ray photoelectron spectroscopy and atomic force microscopy verified the presence of poly(N-acryloylmorpholine) (poly(NAM)) on silicon wafers. The grafting density (σ) and the average distance between grafting points (D) were estimated to be 0.58 chains/nm2 and 1.5 nm, respectively. The ratio of D value to radius of gyration (Rg) value is smaller than 1 (D/2Rg < 1), which corresponds to the brush regime of all grafted poly(NAM) films.

Impact of Membrane Modification and Surface Immobilization Techniques on the Hemocompatibility of Hemodialysis Membranes: A Critical Review

Despite significant research efforts, hemodialysis patients have poor survival rates and low quality of life. Ultrafiltration (UF) membranes are the core of hemodialysis treatment, acting as a barrier for metabolic waste removal and supplying vital nutrients. So, developing a durable and suitable membrane that may be employed for therapeutic purposes is crucial. Surface modificationis a useful solution to boostmembrane characteristics like roughness, charge neutrality, wettability, hemocompatibility, and functionality, which are important in dialysis efficiency. The modification techniques can be classified as follows: (i) physical modification techniques (thermal treatment, polishing and grinding, blending, and coating), (ii) chemical modification (chemical methods, ozone treatment, ultraviolet-induced grafting, plasma treatment, high energy radiation, and enzymatic treatment); and (iii) combination methods (physicochemical). Despite the fact that each strategy has its own set of benefits and drawbacks, all of these methods yielded noteworthy outcomes, even if quantifying the enhanced performance is difficult. A hemodialysis membrane with outstanding hydrophilicity and hemocompatibility can be achieved by employing the right surface modification and immobilization technique. Modified membranes pave the way for more advancement in hemodialysis membrane hemocompatibility. Therefore, this critical review focused on the impact of the modification method used on the hemocompatibility of dialysis membranes while covering some possible modifications and basic research beyond clinical applications.

Artificial Extracellular Matrix Composed of Heparin-Mimicking Polymers for Efficient Anticoagulation and Promotion of Endothelial Cell Proliferation

Heparin-mimicking polymers have emerged as an alternative to heparin to construct effective and safe anticoagulant surfaces. However, the present heparin-mimicking polymers are usually limited to the combinations of glucose and sulfonic acid units, and the structure origin of their anticoagulant properties remains vague. Inspired by the structure of natural heparin, we synthesized a series of novel heparin-mimicking polymers (named GSAs) composed of three units, glucose, sulfonic acid, and carboxylic acid. Then, we constructed artificial extracellular matrices composed of GSAs and two typical cationic polymers, polyethyleneimine and chitosan, to investigate the anticoagulation and endothelialization of GSAs. By changing the ratio of the three units, their functions in the matrices were studied systematically. We found that an increase in the sulfonic acid content enhanced surface anticoagulant activity, an increase in glucose and sulfonic acid content promoted the proliferation of human umbilical vein vascular endothelial cells, and an increase in the carboxylic acid content inhibited the adherence of human umbilical vein vascular smooth muscle cells. This work uncovers the important role of the GSAs structure to the anticoagulation properties, which sheds new light on the design and preparation of heparin-mimicking polymers for practical engineering applications.

A dual initiator approach for oxygen tolerant RAFT polymerization

Reversible-deactivation radical polymerizations are privileged approaches for the synthesis of functional and hybrid materials. A bottleneck for conducting these processes is the need to maintain oxygen free conditions. Herein we report a broadly applicable approach to "polymerize through" oxygen using the synergistic combination of two radical initiators having different rates of homolysis. The in situ monitoring of the concentrations of oxygen and monomer simultaneously provided insight into the function of the two initiators and enabled the identification of conditions to effectively remove dissolved oxygen and control polymerization under open-to-air conditions. By understanding how the surface area to volume ratio of reaction vessels influence open-to-air polymerizations, well-defined polymers were produced using acrylate, styrenic, and methacrylate monomers, which each represent an expansion of scope for the "polymerizing through" oxygen approach. Demonstration of this method in tubular reactors using continuous flow chemistry provided a more complete structure-reactivity understanding of how reaction headspace influences PTO RAFT polymerizations.

PET-RAFT Increases Uniformity in Polymer Networks

Photoinduced electron/energy transfer (PET)-reversible addition-fragmentation chain transfer polymerization (RAFT) and conventional photoinitiated RAFT were used to synthesize polymer networks. In this study, two different metal catalysts, namely, tris[2-phenylpyridinato-C2,N]iridium(III) (Ir(ppy)₃) and zinc tetraphenylporphyrin (ZnTPP), were selected to generate two different catalytic pathways, one with Ir(ppy)₃ proceeding through an energy-transfer pathway and one with ZnTPP proceeding through an electron-transfer pathway. These PET-RAFT systems were contrasted against a conventional photoinitated RAFT process. Mechanically robust materials were generated. Using bulk swelling ratios and degradable cross-linkers, the homogeneity of the networks was evaluated. Especially at high primary chain length and cross-link density, the PET-RAFT systems generated more uniform networks than those made by conventional RAFT, with the electron transfer-based ZnTPP giving superior results to those of Ir(ppy)₃. The ability to deactivate radicals either by RAFT exchange or reversible coupling in PET RAFT was proposed as the mechanism that gave better control in PET-RAFT systems.