Reversible Addition-fragmentation Chain Transfer Research Articles

Preparation and characterization of polydopamine and n-butyl methacrylate copolymer coatings on titanium-nickel alloy stents.

Cardiovascular diseases pose a significant global health threat, and stents play a crucial role in managing these diseases. However, challenges exist with respect to the poor adhesion of stent coatings. Cardiac stents are often composed of titanium-nickel (TiNi) alloys as the metallic component and poly(n-butyl methacrylate) (PBMA) as the coating. The poor adhesion of PBMA to TiNi alloy surface may cause detachment and subsequent thrombosis post-implantation. This study utilizes Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization to synthesize a novel block copolymer, PBMA-b-PVP, composed of PBMA and poly(N-vinylpyrrolidone) (PVP). TiNi alloy surfaces are functionalized with polydopamine (PDA) to enhance polymer coating adhesion. PBMA-b-PVP exhibits a remarkable improvement in adhesion from class 5 to class 0 and high coating stability after a 15 days immersion in a phosphate buffer solution. The corrosion current density is reduced by 44% with the incorporation of PDA into PBMA-b-PVP coatings, suggesting high corrosion resistance. PDA-functionalized coatings promote cell viability without cytotoxicity, suggesting high biocompatibility. This study provides a robust strategy for preparing stent coatings with high adhesion, corrosion resistance, and biocompatibility.

Radical promoted cationic RAFT polymerization by photo electron transfer reaction

A radical promoted cationic reversible addition–fragmentation chain transfer (RAFT) polymerization of various vinyl ethers via photo electron transfer reaction was developed and applied in photocuring.

One stone two birds: from one azlactone-functionalized monomer to a heterofunctional diblock copolymer

An innovative combination of RAFT polymerization using easy-to-implement conditions and post-polymerization modification by click aminolysis for efficient preparation of heterofunctional diblock copolymers derived from vinyl azlactone.

Lowest gelation concentration in a complex-coacervate-driven self-assembly system, achieved by redox-RAFT synthesis of high molecular weight block polyelectrolytes.

The objective of this work was to synthesize high molecular weight polyelectrolyte complex (PEC) micelles that are effective in controlling the rheology of aqueous solutions at low concentrations, paving the way for industrial applications of thickeners based on the principle of electrostatic self-assembly. Redox-initiated RAFT (reversible addition-fragmentation chain-transfer) polymerization was used to obtain anionic block polyelectrolytes based on poly(sodium 2-acrylamido-2-methylpropane sulfonate) and poly(acrylamide)-poly(AMPS)-block-poly(AM) (di-block) and poly(AMPS)-block-poly(AM)-block-poly(AMPS) (tri-block), with molecular weights of 237 kDa and 289 kDa and polydispersities of 1.29 and 1.34, respectively. A random poly(AMPS)-co-poly(AM) copolymer was also synthesized for comparison. PEC micelles were obtained upon mixing with cationic poly(N-[3-(dimethylamino)propyl]methacrylamide hydrochloride) - poly(DMAPMA), forming viscoelastic gels at unprecedented low concentrations of <3 wt% for the di-block and <1 wt% for the tri-block, which to date is the lowest demonstrated gelation concentration for a synthetic PEC micelle system. Differences between tri-block and di-block architectures are discussed, with the former being more affected by the addition of salt, which is attributed to percolated network breakdown. The random co-polymer was shown not to be an effective thickener but displayed a surprising lack of phase separation upon coacervation. The assemblies were characterized using dynamic light scattering (DLS) and cryo transmission electron microscopy (cryoTEM), revealing spherical micelles with a diameter of approximately 200 nm for the diblock and a mixture of spherical micelles and network particles for the tri-block PEC micelles. The micelles were not affected by dilution down to a polymer concentration of 7.8 × 10-4% (approx. 0.03 μM). Responsiveness to salinity, pH, and temperature was studied using DLS, revealing a critical NaCl concentration of 1.1 M for the block copolymer micelles.

Bio-photo-Fenton-like RAFT polymerization under blue light

In this manuscript, we report a natural photoinitiation system for polymer synthesis by employing a combination of riboflavin 5’-monophosphate sodium salt (vitamin B2) and hydrogen peroxide, later glucose/glucose oxidase system,...

Injectable, self-healing and degradable dynamic hydrogels with tunable mechanical properties and stability by thermal-induced micellization.

Dynamic hydrogels possessing injectable, degradable and self-healing abilities have attracted considerable attention in the biomedical field in recent years, but it is difficult to tune the mechanical properties and stability of conventional dynamic hydrogels. In this work, we synthesized ABA-triblock copolymers via RAFT polymerization, where the A block consisted of thermo-sensitive poly(N-isopropylacrylamide-co-diacetone acrylamide) and the B block was hydrophilic poly(acrylamide). Subsequently, dynamic hydrogels were obtained based on the acylhydrazone bonds between the triblock copolymers and adipic acid dihydrazide (ADH). The obtained hydrogels exhibited injectable and self-healable abilities. In response to the thermal-induced micellization of their temperature-responsive blocks, the mechanical strength of the hydrogels not only increased, but also they exhibited high stability even at pH 2.0. Moreover, the hydrogel in the stable state could be degraded by the fracture of its trithiocarbonate groups. In addition, the hydrogels exhibited good cytocompatibility and controlled release behavior for doxorubicin (DOX). Considering these attractive tunable properties, these dynamic hydrogels show various potential applications in the biomedical field, such as drug carriers and cell or tissue engineering scaffolds.

Aqueous photo-RAFT polymerization under ambient conditions: synthesis of protein–polymer hybrids in open air

A photoinduced reversible addition-fragmentation chain-transfer (photo-RAFT) polymerization technique in the presence of sodium pyruvate (SP) and pyruvic acid derivatives was developed.

Block copolymer synthesis in ionic liquid via polymerisation-induced self-assembly: a convenient route to gel electrolytes.

We report for the first time a reversible addition-fragmentation chain transfer polymerisation-induced self-assembly (RAFT-PISA) formulation in ionic liquid (IL) that yields worm gels. A series of poly(2-hydroxyethyl methacrylate)-b-poly(benzyl methacrylate) (PHEMA-b-PBzMA) block copolymer nanoparticles were synthesised via RAFT dispersion polymerisation of benzyl methacrylate in the hydrophilic IL 1-ethyl-3-methyl imidazolium dicyanamide, [EMIM][DCA]. This RAFT-PISA formulation can be controlled to afford spherical, worm-like and vesicular nano-objects, with free-standing gels being obtained over a broad range of PBzMA core-forming degrees of polymerisation (DPs). High monomer conversions (≥96%) were obtained within 2 hours for all PISA syntheses as determined by 1H NMR spectroscopy, and good control over molar mass was confirmed by gel permeation chromatography (GPC). Nanoparticle morphologies were identified using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), and further detailed characterisation was conducted to monitor rheological, electrochemical and thermal characteristics of the nanoparticle dispersions to assess their potential in future electronic applications. Most importantly, this new PISA formulation in IL facilitates the in situ formation of worm ionogel electrolyte materials at copolymer concentrations >4% w/w via efficient and convenient synthesis routes without the need for organic co-solvents or post-polymerisation processing/purification. Moreover, we demonstrate that the worm ionogels developed in this work exhibit comparable electrochemical properties and thermal stability to that of the IL alone, showcasing their potential as gel electrolytes.

Impact of a poly(ethylene glycol) corona block on drug encapsulation during polymerization induced self-assembly.

Polymerization induced self-assembly (PISA) provides a facile platform for encapsulating therapeutics within block copolymer nanoparticles. Performing PISA in the presence of a hydrophobic drug alters both the nanoparticle shape and encapsulation efficiency. While previous studies primarily examined the interactions between the drug and hydrophobic core block, this work explores the impact of the hydrophilic corona block on encapsulation. Poly(ethylene glycol) (PEG) and poly(2-hydroxypropyl methacrylate) (PHPMA) are used as the model corona and core blocks, respectively, and phenylacetic acid (PA) is employed as the model drug. Attachment of a dithiobenzoate end group to the PEG homopolymer - transforming it into a macroscopic reversible addition-fragmentation chain transfer agent - causes the polymer to form a small number of nanoscopic aggregates in solution. Adding PA to the PEG solution encourages further aggregation and macroscopic phase separation. During the PISA of PEG-PHPMA block copolymers, inclusion of PA in the reaction mixture promotes faster nucleation of spherical micelles. Although increasing the targeted PA loading from 0 to 20 mg mL-1 does not affect the micelle size or shape, it alters the drug spatial distribution within the PISA microenvironment. PA partitions into either PEG-PHPMA micelles, deuterium oxide, or other polymeric species - including PEG aggregates and unimer chains. Increasing the targeted PA loading changes the fraction of drug within each encapsulation site. This work indicates that the corona block plays a critical role in dictating drug encapsulation during PISA.

Visible light-triggered non-deoxygenated PET–RAFT polymerization by heterogeneous conjugated microporous polymer photocatalysts

A novel pyrene-based heterogeneous conjugated microporous polymer photocatalyst can mediate oxygen-tolerant PET–RAFT polymerization without prior deoxygenation.

Green synthesis of polymer materials via enzyme- initiated RAFT polymerization

In this review, various strategies of enzyme-catalysed RAFT polymerization are discussed for the synthesis of sustainable and precision polymers via green polymer chemistry.

Solvent effects on surface-grafted and solution-born poly[N-(2-hydroxypropyl)methacrylamide] during surface-initiated RAFT polymerization

Solvent effects influence grafting density and cause discrepancy between molar mass of surface-grafted and solution-born poly[N-(2-hydroxypropyl) methacrylamide] during surface-initiated RAFT polymerization.

Exploring ferrocene-directed photo-Fenton initiation of RAFT polymerization

Exploring ferrocene-directed photo-Fenton initiation of RAFT polymerization

Amide-Containing Bottlebrushes via Continuous-Flow Photoiniferter Reversible Addition-Fragmentation Chain Transfer Polymerization: Micellization Behavior.

Herein, a series of ternary amphiphilic amide-containing bottlebrushes were synthesized by photoiniferter (PI-RAFT) polymerization of macromonomers in continuous-flow mode using trithiocarbonate as a chain transfer agent. Visible light-mediated polymerization of macromonomers under mild conditions enabled the preparation of thermoresponsive copolymers with low dispersity and high yields in a very short time, which is not typical for the classical reversible addition-fragmentation chain transfer process. Methoxy oligo(ethylene glycol) methacrylate and alkoxy(C12-C14) oligo(ethylene glycol) methacrylate were used as the basic monomers providing amphiphilic and thermoresponsive properties. The study investigated how modifying comonomers, acrylamide (AAm), methacrylamide (MAAm), and N-methylacrylamide (-MeAAm) affect the features of bottlebrush micelle formation, their critical micelle concentration, and loading capacity for pyrene, a hydrophobic drug model. The results showed that the process is scalable and can produce tens of grams of pure copolymer per day. The unmodified copolymer formed unimolecular micelles at temperatures below the LCST in aqueous solutions, as revealed by DLS and SLS data. The incorporation of AAm, MAAm, and N-MeAAm units resulted in an increase in micelle aggregation numbers. The resulting bottlebrushes formed uni- or bimolecular micelles at extremely low concentrations. These micelles possess a high capacity for loading pyrene, making them a promising choice for targeted drug delivery.

RAFT polymerization of renewable monomers with dithiobenzoates: Effect of Z-group substituents and reaction conditions

The use of renewable polymer feedstocks has attracted significant attention recently due to increased concerns about petrochemical-based materials and limited fossil-based resources. As a promising candidate, lignin-derived monomers have been polymerized via controlled radical polymerization to yield bio-based materials. Arguably, the most commonly employed polymerization methodology is reversible-addition-fragmentation chain-transfer (RAFT) polymerization which utilizes, almost exclusively, 2-cyano-2-propyl benzodithioate as a chain transfer agent (CTA). Despite the robustness of this approach, polymerization of lignin-derived methacrylates is far more challenging than of the commonly used monomers (e.g. methyl methacrylate), often resulting in polymers with moderate control over the molecular weight and dispersity (Đ). To improve control over the RAFT polymerization, we investigate here a series of 2-cyano-2-propyl benzodithioate derivatives, where the electronic properties of the Z group were systematically altered. The introduction of electron-withdrawing groups in the para-position of the phenyl ring of the Z group increased control over the polymerization by improving the chain transfer coefficient of the CTA, resulting in enhanced control over molecular weights and lower Đs. Conversely, the incorporation of electron-donating groups had the opposite effect. 2-cyano-2-propyl 4-cyanobenzodithioate was found to be the optimal CTA for the polymerization of a series of lignin-derived monomers resulting in Đs < 1.25. The robustness of the system was highlighted by the synthesis of higher molecular weights polymers and the efficient chain-extension of macroCTAs; the latter case yielding bio-based block copolymers with a Đ as low as 1.16. This work highlights that RAFT polymerization can, upon judicious optimization, be successfully employed for the synthesis of renewable polymers.

Dual-templating synthesis of superhydrophobic Fe3O4/PSt porous composites for highly efficient oil-water separation

Fe3O4/PSt porous composites with low density, interconnected network structure and superhydrophobic were prepared successfully by a dual-templating method, including High Internal Phase Emulsion (HIPEs) template method and the introduction of organic template species. It was worth mentioning that a novel amphiphilic di-block copolymers P(DMAEMA-b-St) were prepared as emulsifier by reversible addition fragmentation chain transfer (RAFT) polymerization method. At the same time, the effects of PS block length, emulsifier content, Fe3O4 content, DVB content and dispersed phase proportion on HIPEs droplet size and the corresponding polyHIPEs oil absorption were researched. The results showed that the oil adsorption capacity of 9.43 g/g toward toluene under optimal conditions. Subsequently, adsorption isotherm and adsorption kinetics were investigated. The results were shown that the adsorption of oil on adsorbent followed Freundlich model and pseudo-second-order (PSO) model. In addition, the adsorption experiments on a variety of oils demonstrated the wide applicability of Fe3O4/PSt porous composites. The cycling experiments proved that the Fe3O4/PSt porous composites had excellent cycling ability, were easy to recover and could be reused for multiple times. Finally, the adsorption column experiments showed that Fe3O4/PSt porous composites had powerful potential for industrial applications.

Elucidating the Role of Optical Activity of Polymers in Protein-Polymer Interactions.

Proteins are biomolecules with potential applications in agriculture, food sciences, pharmaceutics, biotechnology, and drug delivery. Interactions of hydrophilic and biocompatible polymers with proteins may impart proteolytic stability, improving the therapeutic effects of biomolecules and also acting as excipients for the prolonged storage of proteins under harsh conditions. The interactions of hydrophilic and stealth polymers such as poly(ethylene glycol), poly(trehalose), and zwitterionic polymers with various proteins are well studied. This study evaluates the molecular interactions of hydrophilic and optically active poly(vitamin B5 analogous methacrylamide) (poly(B5AMA)) with model proteins by fluorescence spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and circular dichroism (CD) spectroscopy analysis. The optically active hydrophilic polymers prepared using chiral monomers of R-(+)- and S-(-)-B5AMA by the photo-iniferter reversible addition fragmentation chain transfer (RAFT) polymerization showed concentration-dependent weak interactions of the polymers with bovine serum albumin and lysozyme proteins. Poly(B5AMA) also exhibited a concentration-dependent protein stabilizing effect at elevated temperatures, and no effect of the stereoisomers of polymers on protein thermal stability was observed. NMR analysis, however, showed poly(B5AMA) stereoisomer-dependent changes in the secondary structure of proteins.

Controlled polymerization in microfluidics: Advancement in nanogel synthesis

AbstractThis comprehensive review provides a detailed examination of controlled polymerization in the development of nanogels‐based microfluidic devices. Here, we have explored the integration of atom transfer radical polymerization (ATRP) and reversible addition‐fragmentation chain transfer (RAFT) techniques within microfluidic platforms for the synthesis of nanogels. The synergistic combination of ATRP and RAFT with microfluidics has emerged as a powerful tool for precise control over polymerization reactions, enabling the fabrication of well‐defined, multifunctional nanogels with tailored properties. The review begins with a thorough introduction to the principles of ATRP and RAFT, highlighting their respective advantages in controlled radical polymerization. Subsequently, it elucidates the principles of microfluidics and its profound impact on polymerization processes. The merging of these techniques enables precise control over reaction kinetics, monomer conversions, and molecular weight distributions, facilitating the synthesis of nanogels with unprecedented precision and reproducibility. Furthermore, this review delves into the chemical mechanisms underlying ATRP and RAFT reactions in microfluidic environments, emphasizing the role of various initiators, catalysts, and chain transfer agents. Special attention is given to the impact of microscale flow conditions on reaction kinetics and polymer structure. In addition, the review discusses emerging trends in the field, such as the incorporation of novel monomers and the exploration of environmentally benign reaction conditions.Highlights The controlled polymerization is the mechanism by which we can obtain tailormade material. The nanogel synthesis must ensure the gelation to be in confined dimensions here microfluidics plays key role.

Temperature response behavior of poly(1-vinyl-3-methylimidazole dimethyl phosphate-co-N-isopropylacrylamide) in aqueous and ester solutions driven by hydrogen bonding

A series of poly(1-vinyl-3-methylimidazole dimethyl phosphate-co-N-isopropylacrylamide) oligomers was synthesized by reversible addition-fragmentation chain transfer polymerization. The co-oligomers exhibited a pH-tunable lower critical solution temperature (LCST) phase transition in aqueous solutions. By changing the pH of the aqueous solution (HCI), the hydrogen bonding between the internal molecules of the co-oligomers and water molecules was weakened, which effectively reduced the cloud-point temperature. Poly(1-vinyl-3-methylimidazole dimethyl phosphate-co-N-isopropylacrylamide) oligomers exhibit an upper critical solution temperature (UCST) type of phase transition in an ester solution, which is associated with the formation and breaking of hydrogen bonds within the co-oligomers molecules. FT-IR analysis revealed the effect of temperature on hydrogen bonding between the functional groups. Energy decomposition, Electrostatic Potential (ESP), Atoms-in-Molecules (AIM), and Interaction region indicator (IRI) analyses demonstrated the presence of hydrogen bond donors N–H and imidazole ring C–H, and hydrogen bond acceptors C = O and P = O in the co-oligomers. The sites of hydrogen bonding between the co-oligomers and the solvent molecules as well as intermolecular forces were found to be the main factors contributing to the LCST/UCST-type phase transition.

PH-sensitive multi-arm star polyampholytes: A novel approach for simultaneous adsorption of anionic and cationic dyes

This study introduces star-shaped polyampholyte adsorbents, comprising poly(acrylic acid) cores and poly(2-(dimethylamino)ethyl methacrylate) arms. Reversible addition fragmentation chain-transfer (RAFT) polymerization and distillation-precipitation approach were utilized to prepare star polyampholytes in different monomer/RAFT agent ratios (70, 130, and 200). Well-defined and star-like structures were validated employing proton nuclear magnetic resonance, gel permeation chromatography, and differential scanning calorimetry. pH-dependent self-assembled particle morphologies were scrutinized using field emission scanning electron microscopy and dynamic light scattering. The adsorbents exhibited substantial potential for efficient dye removal from wastewater, attaining up to 76.6% adsorption (pH = 2) for methylene orange and 48.3% (pH = 10) for methylene blue in single-dye systems using Star AA_DMAEMA_200 and Star AA_DMAEMA_130, respectively. Dual-dye systems revealed captivating synergistic interactions, showcasing intricate behaviors between dyes. The influence of molecular weight intricacies on adsorption dynamics unveiled a spectrum of diverse trends, underscoring the absorbents' versatility. These findings not only deepen our understanding of the adsorption process but also underscore the paramount potential of star-shaped polyampholyte absorbents in addressing complex environmental color removal challenges.