Photoinduced Electron Transfer Reversible Addition Fragmentation Research Articles

Antiviral Polymer Brushes by Visible-Light-Induced, Oxygen-Tolerant Covalent Surface Coating

This work presents a novel route for creating metal-free antiviral coatings based on polymer brushes synthesized by surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain transfer (SI-PET-RAFT) polymerization, applying eosin Y as a photocatalyst, water as a solvent, and visible light as a driving force. The polymer brushes were synthesized using N-[3-(decyldimethyl)-aminopropyl] methacrylamide bromide and carboxybetaine methacrylamide monomers. The chemical composition, thickness, roughness, and wettability of the resulting polymer brush coatings were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), water contact angle measurements, and ellipsometry. The antiviral properties of coatings were investigated by exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and avian influenza viruses, with further measurement of residual viable viral particles. The best performance was obtained with Cu surfaces, with a ca. 20-fold reduction of SARS-Cov-2 and a 50-fold reduction in avian influenza. On the polymer brush-modified surfaces, the number of viable virus particles decreased by about 5-6 times faster for avian flu and about 2-3 times faster for SARS-CoV-2, all compared to unmodified silicon surfaces. Interestingly, no significant differences were obtained between quaternary ammonium brushes and zwitterionic brushes.

Mechanistic Insights into Oxygen Tolerance of Graphitic Carbon Nitride-Mediated Heterogeneous Photoinduced Electron Transfer-Reversible Addition Fragmentation Chain Transfer Polymerization

Mechanistic Insights into Oxygen Tolerance of Graphitic Carbon Nitride-Mediated Heterogeneous Photoinduced Electron Transfer-Reversible Addition Fragmentation Chain Transfer Polymerization

Porphyrin-based donor-acceptor COFs as efficient and reusable photocatalysts for PET-RAFT polymerization under broad spectrum excitation.

Covalent organic frameworks (COFs) are crystalline and porous organic materials attractive for photocatalysis applications due to their structural versatility and tunable optical and electronic properties. The use of photocatalysts (PCs) for polymerizations enables the preparation of well-defined polymeric materials under mild reaction conditions. Herein, we report two porphyrin-based donor–acceptor COFs that are effective heterogeneous PCs for photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT). Using density functional theory (DFT) calculations, we designed porphyrin COFs with strong donor–acceptor characteristics and delocalized conduction bands. The COFs were effective PCs for PET-RAFT, successfully polymerizing a variety of monomers in both organic and aqueous media using visible light (λmax from 460 to 635 nm) to produce polymers with tunable molecular weights (MWs), low molecular weight dispersity, and good chain-end fidelity. The heterogeneous COF PCs could also be reused for PET-RAFT polymerization at least 5 times without losing photocatalytic performance. This work demonstrates porphyrin-based COFs that are effective catalysts for photo-RDRP and establishes design principles for the development of highly active COF PCs for a variety of applications.

PET-RAFT copolymerization of vinyl acetate and acrylic acid

Photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization of vinyl acetate (VAc) and acrylic acid (AA) was successfully realized in methanol at room temperature under blue LED (420 nm, 6 mW/cm2) irradiation with xanthate as RAFT agent and fac-[Ir(ppy)3] as the photocatalyst. The well-defined copolymers of poly(VAc-co-AA) with controlled molecular weights (Mn,GPC) and polydispersity index (PDI) were successfully obtained. The polymerization revealed the behaviors of controlled/living polymerization, which was verified by the observed linear relationship of ln([M]0/[M]t) with respect to irradiation time and that of the experimental molecular weights (Mn,GPC) with respect to monomer conversion. GPC curves showed a single peak and shifted to high molecular weights with increasing the irradiation time. The reactivity ratios of VAc and AA were 0.043 and 1.181, respectively in this system. The effect of the amount of fac-[Ir(ppy)3] on PET-RAFT polymerization was investigated. The monomer conversion increased with increasing the amount of fac-[Ir(ppy)3] and the PDI decreased with the increase in the amount of fac-[Ir(ppy)3]. The temporal controllable PET-RAFT polymerization of vinyl acetate (VAc) and acrylic acid (AA) was achieved. The structure of synthesized poly(VAc-co-AA) was characterized by nuclear magnetic resonance spectroscopy (1H NMR) and gel permeation chromatography (GPC), respectively. The extended experiments of poly(VAc-co-AA) with fresh AA was conducted under the irradiation of blue LED, and the results demonstrated that this extension polymerization displayed controlled polymerization behavior. The mechanism was explained in this study.

Dissipative Self-Assembly of Dynamic Multicompartmentalized Microsystems with Light-Responsive Behaviors

Summary Living cells are compartmentalized systems operating far from thermodynamic equilibrium and consume energy from the environment to carry out their functions. The construction of biomimetic synthetic compartments has both scientific and technological value. Despite many advances, the assembly of synthetic compartments that present nonequilibrium behaviors based on dissipative (or transient) self-assembly remains a grand challenge. Here, we describe the design and synthesis of multicompartmental systems with an active microstructure and complex behaviors. By including an artificial pathway for energy dissipation, we demonstrate the autonomous generation of active polymeric systems using a strategy based on polymerization-induced self-assembly (PISA), driven by chemical fuel. Remarkably, these self-organized synthetic systems exhibit a dynamic change in their multicompartmental structures when exposed to light. This work introduces a strategy toward the design and construction of synthetic compartments with a dynamic structure and also presents pathways to engineer materials with spatially controllable structures and functionalities.

Light and magnetism dual-gated photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization

A novel raspberry-like γ-Fe2O3@carbon dot (CD) nanocatalyst was prepared and applied for photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization. The nanocatalyst was found to be an efficient photocatalyst in visible light-regulated PET-RAFT polymerization owing to the oxidative quenching mechanism between the photoexcited γ-Fe2O3@CDs and the RAFT agent in the PET process. Notably, polymerization can be reversibly ceased in the absence of light or under an external magnetic field. The superparamagnetic nature and high saturation magnetization value (∼30.4 emu g−1) of the nanocatalyst contribute to convenient recycling of the nanocatalyst after polymerization. The PET-RAFT polymerization with the nanocatalyst before and after recycling was investigated, which displayed all the characteristics of controlled/living polymerization systems.

Effect of Tertiary Amines on the Photoinduced Electron Transfer-Reversible Addition–Fragmentation Chain Transfer (PET-RAFT) Polymerization

Herein, we report a detailed investigation on the influence of a series of tertiary alkylamine on the rate of the photoinduced electron transfer–reversible addition–fragmentation chain transfer (PE...

PVA Hydrogel Functionalization via PET-RAFT Grafting with Glycidyl Methacrylate and Immobilization with 2-Hydroxypropyltrimethyl Ammonium Chloride Chitosan via Ring-Open Reaction

To solve the biofouling problem of polyvinyl alcohol (PVA) hydrogel as the artificial cornea, glycidyl methacrylate (GMA) and 2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) were grafted on the surface of PVA hydrogel via a new method of photoinduced electron transfer—reversible addition fragmentation chain transfer (PET-RAFT) polymerization and ring-open reaction. Both attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscope (SEM), and thermogravimetric analysis (TGA) confirmed that GMA and HACC were successfully grafted on the surface of PVA hydrogel. A series of experiments to test the hydrophilicity of PVA hydrogel showed that it became hydrophobic due to the introduction of hydrophobic groups after grafting with GMA and HACC. In addition, cytotoxicity in vitro of PVA-g-p(GMA-HACC) hydrogel could be considered as not cytotoxicity according to ISO 10993-5: 2009. The anti-fouling property of hydrogel decreased after grafting with GMA due to the hydrophobic surface, while increased after grafting with HACC due to the steric repulsion of p(GMA-HACC) polymer brush. It’s no doubt that PET-RAFT was a feasible and reliable surface modification method which could be used in many biomolecules due to the excellent advantages.

Scalable Aqueous Reversible Addition–Fragmentation Chain Transfer Photopolymerization-Induced Self-Assembly of Acrylamides for Direct Synthesis of Polymer Nanoparticles for Potential Drug Delivery Applications

The synthesis of polymer nanoparticles for potential drug delivery applications via photoinduced electron transfer–reversible addition–fragmentation chain transfer aqueous dispersion polymerizations employing Eosin Y/triethanol amine as catalytic system is described. A scalable synthesis procedure for the polymerization of poly(dimethyl acrylamide)-b-(poly(diaceteone-stat-dimethyl acrylamide)) is reported under visible light (λmax = 530 nm). A variety of solid contents and block lengths for the solvophilic and solvophobic blocks are investigated, expanding the compositional space of worms, jellyfish, and vesicles using flow chemistry. A simple two-step process using a coupled flow reactor setup is used without the need for intermediate purification.

SI-PET-RAFT: Surface-Initiated Photoinduced Electron Transfer-Reversible Addition-Fragmentation Chain Transfer Polymerization.

In this communication, surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain transfer polymerization (SI-PET-RAFT) is introduced. SI-PET-RAFT affords functionalization of surfaces with spatiotemporal control and provides oxygen tolerance under ambient conditions. All hallmarks of controlled radical polymerization (CRP) are met, affording well-defined polymerization kinetics, and chain end retention to allow subsequent extension of active chain ends to form block copolymers. The modularity and versatility of SI-PET-RAFT is highlighted through significant flexibility with respect to the choice of monomer, light source and wavelength, and photoredox catalyst. The ability to obtain complex patterns in the presence of air is a significant contribution to help pave the way for CRP-based surface functionalization into commercial application.

Surface modification PVA hydrogel with zwitterionic via PET‐RAFT to improve the antifouling property

ABSTRACTTo improve the antifouling property, polyvinyl alcohol hydrogel was successfully grafted with [2‐(methacryloyloxy) ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide (MEDSAH) via photoinduced electron transfer–reversible addition–fragmentation chain transfer (PET‐RAFT) polymerization under a 10 W blue (450–460 nm) light‐emitting diodes. It is surprising that the reaction could be performed in the presence of oxygen, which meant that the reaction has a great prospect of industrialization. The highest grafting percentage (GP) was 55.77% by adding triethylamine and changed the MEDSAH usage in the absence of oxygen. Thermal gravimetric analysis exhibited that grafted MEDSAH affects the thermal property of PVA hydrogel. Also, there was no influence on the ultraviolet–visible transmittance, and the PVA‐g‐pMEDSAH hydrogel became hydrophilicity after grafting. Moreover, in vitro cytotoxicity of both PVA and PVA‐g‐pMEDSAH hydrogel was noncytotoxic according to ISO 10993‐2009. The antifouling property of PVA‐g‐pMEDSAH hydrogel was increased about 53.05%. Thus, the PVA‐g‐pMEDSAH hydrogel can be an ideal optical biomaterial candidate. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47653.

Surface modification of PVA hydrogel membranes with carboxybetaine methacrylate via PET-RAFT for anti-fouling

In this study, we grafted brush-like CBMA copolymer brushes onto the surface of PVA hydrogel membrane through photo-induced electron transfer–reversible addition fragmentation chain transfer (PET-RAFT) polymerization. ATR-FTIR, XPS, AFM, UV–Vis absorption spectra and elemental analysis were adopted to characterize the hydrogels, and equilibrium swelling, water contact angle, vitro cytotoxicity assay, protein adsorption and cells adhesion experiments were used to evaluate the related property of hydrogels. The results of ATR-FTIR and XPS showed that pCBMA was successfully grafted onto the surface of PVA hydrogel membrane. The Ra roughness of hydrogel surface in AFM increased slightly from 5.44 nm to 6.12 nm. Transmittance of the PVA-g-pCBMA hydrogel in the visible range (380 nm-780 nm) was remaining at 91.2%–97.0%. The optimal reaction conditions (CPADB: 1.20 mmol/L, Eosin Y: 0.03 mmol/L and CBMA: 358 mmol/L) were confirmed through control experiments. The equilibrium swelling and water contact angle showed that the swelling ratio increased from 2.06 cm3 g−1 to 3.65 cm3 g−1, while the water contact angle decreased from 45.94° to 18.06° with the increase of grafting ratio (23.92%–55.18%). In vitro cytotoxicity assay by CCK-8 showed that the cells relative viability remained at least 90.55%. Anti-protein adsorption experiment illustrated approximately 57.2% improvement of anti-protein capacity at 37 °C, while cells adhesion experiment also showed about 64.57% improvement of anti-cells capacity. These results revealed the applicability of the oxygen tolerant PET-RAFT mechanism on the PVA modification and it was effective, feasible and non-cytotoxic method to prepare the other functional PVA hydrogel membrane.

A versatile signal-enhanced ECL sensing platform based on molecular imprinting technique via PET-RAFT cross-linking polymerization using bifunctional ruthenium complex as both catalyst and sensing probes

Molecularly imprinted technique (MIT) has proven to be a significant tool in the analyzing area in virtue of its obvious advantages such as specific recognition, favorable stability to high temperature and higher sensitivity. Electrochemiluminescence (ECL) technology has also been receiving enormous attention as a powerful tool in sensing fields. However, sensors based on the combination of MIT and ECL technologies have seldom been reported yet. Herein, we find that Ru(bpy)32+ cannot only work as an efficient catalyst for photo-induced electron transfer–reversible addition–fragmentation chain transfer (PET-RAFT) polymerization, but also as a sensing probe for ECL sensor. Based on this, we successfully construct ECL sensors via the combination of MIT and ECL techniques. In details, poly(methacrylic acid) (PMAA) and cross-linked PMAA were synthesized first via a well-controlled PET-RAFT polymerization using Ru(bpy)32+ as catalyst under illumination of visible light with a wavelength of 460 nm, as confirmed by 1H NMR and gel permeation chromatography (GPC). Then, negatively-charged Au nanoparticles (AuNPs) with average sizes of 20 nm were prepared and modified with Ru(bpy)32+ via electrostatic incorporation. MIPs were prepared on the surface of AuNPs using melamine (MEL) as the template via PET-RAFT controlled cross-linking polymerization. The MIPs modified AuNPs (AuNPs-MIPs) were then fixed on the surface of working electrode with Nafion to achieve a solid-state ECL sensing platform employing Ru(bpy)32+ as the ECL probes. The as-prepared sensor showed a wide detection range of 5.0 × 10–13 − 5.0 × 10−6 mol/L and a low detection limit of 1.0 × 10–13 mol/L (S/N ≥ 3) was reached in the detection of MEL. Moreover, further tests for analyzing MEL structural analogues proved that the constructed ECL sensing platform could be utilized to detect various substances via specific recognitions.

Towards Sequence‐Controlled Antimicrobial Polymers: Effect of Polymer Block Order on Antimicrobial Activity

AbstractSynthetic polymers have shown promise in combating multidrug‐resistant bacteria. However, the biological effects of sequence control in synthetic antimicrobial polymers are currently not well understood. As such, we investigate the antimicrobial effects of monomer distribution within linear high‐order quasi‐block copolymers consisting of aminoethyl, phenylethyl, and hydroxyethyl acrylamides made in a one‐pot synthesis approach via photoinduced electron transfer–reversible addition–fragmentation chain transfer polymerisation (PET‐RAFT). Through different combinations of monomer/polymer block order, antimicrobial and haemolytic activities are tuneable in a manner comparable to antimicrobial peptides.

ZnO as photocatalyst for photoinduced electron transfer–reversible addition–fragmentation chain transfer of methyl methacrylate

AbstractIn this article, photoinduced electron transfer–reversible addition–fragmentation chain transfer (PET‐RAFT) polymerization of methyl methacrylate (MMA) was investigated at moderate temperature in N,N‐dimethylformamide with ZnO as photocatalyst. The polymerization has a living characteristic: a linear increase in molecular weight (Mn,GPC), good agreement between experimental (Mn,GPC) and theoretical molecular weights (Mn,th), a decrease in molecular weight distribution (Mw/Mn) with increasing monomer conversion, and chain extension. The PET‐RAFT polymerization of MMA can be regulated by switching “ON” and “OFF” the light.

Controlled radical polymerization of vinyl ketones using visible light

Herein we report the photoinduced electron transfer–reversible addition–fragmentation chain transfer (PET-RAFT) polymerization of a range of vinyl ketone monomers including methyl, ethyl and phenyl derivatives, using Eosin Y as an organic photoredox catalyst and visible light.

Organo-photocatalysts for photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization

In this work, we demonstrate the use of organophotoredox catalysts under visible light to perform photoinduced electron transfer-reversible addition fragmentation chain transfer (PET-RAFT) for the polymerization of methacrylate monomers.

Photoinduced Electron Transfer–Reversible Addition–Fragmentation Chain Transfer (PET-RAFT) Polymerization of Vinyl Acetate andN-Vinylpyrrolidinone: Kinetic and Oxygen Tolerance Study

Photoinduced electron transfer–reversible addition–fragmentation chain transfer (PET-RAFT) polymerization was employed for the polymerization of unconjugated monomers, including vinyl acetate, vinyl pivalate, N-vinylpyrrolidinone, dimethyl vinylphosphonate, vinyl benzoate, and N-vinylcarbazole, in the presence of low concentration (ppm range) of photoredox catalyst, fac-[Ir(ppy)3], under low energy visible light irradiation. Kinetic studies of vinyl acetate indicated excellent control of molecular weights and molecular weight distributions (Mw/Mn = 1.09–1.2), even with high monomer conversion (>75%), in different catalyst concentrations. High molecular weights of poly(vinyl acetate) (Mn > 100 000 g/mol) and poly(N-vinylpyrrolidinone) (Mn > 40 000 g/mol) with low dispersities (Mw/Mn < 1.25) were obtained in bulk polymerizations. Moreover, the online kinetic study using Fourier transform near-infrared (FTNIR) showed comparable kinetic rates for the polymerizations in the absence and presence of relatively l...

Oxygen Tolerance Study of Photoinduced Electron Transfer–Reversible Addition–Fragmentation Chain Transfer (PET-RAFT) Polymerization Mediated by Ru(bpy)3Cl2

This study reports a highly efficient photoredox catalyst, Ru(bpy)3Cl2, capable of controlling the polymerization of methacrylates, acrylates, and acrylamides in the presence of thiocarbonylthio compounds via a photoinduced electron transfer–reversible addition–fragmentation chain (PET-RAFT) process. This polymerization technique was performed in a closed vessel in the presence or absence of air. Online Fourier transform near-infrared spectroscopy (FTNIR) was employed to monitor the monomer conversions of methyl methacrylate, methyl acrylate, and N,N′-dimethylacrylamide in the presence or absence of air. Interestingly, after an induction period, the polymerization proceeded in the presence of air to yield well-defined polymers (PDI < 1.20). The polymers were characterized by 1H NMR, UV–vis spectroscopy, and gel permeation chromatography. Excellent end-group retention was also demonstrated by NMR, UV–vis, and successive chain extensions of the resulting homopolymers to yield diblock and multiblock copolymers (decablock copolymers).