Transfer-reversible Addition-fragmentation Chain Transfer Polymerization Research Articles

Oxygen-Tolerant Fabrication of Large-Area Hydrogel Films via Photoinduced Electron/Energy Transfer-Reversible Addition–Fragmentation Chain Transfer Polymerization

Oxygen-Tolerant Fabrication of Large-Area Hydrogel Films via Photoinduced Electron/Energy Transfer-Reversible Addition–Fragmentation Chain Transfer Polymerization

Unleashing the Power of PET-RAFT Polymerization: Journey from Porphyrin-Based Photocatalysts to Combinatorial Technologies and Advanced Bioapplications.

The emergence of photoinduced energy/electron transfer-reversible addition-fragmentation chain transfer polymerization (PET-RAFT) not only revolutionized the field of photopolymerization but also accelerated the development of porphyrin-based photocatalysts and their analogues. The continual expansion of the monomer family compatible with PET-RAFT polymerization enhances the range of light radiation that can be harnessed, providing increased flexibility in polymerization processes. Furthermore, the versatility of PET-RAFT polymerization extends beyond its inherent capabilities, enabling its integration with various technologies in diverse fields. This integration holds considerable promise for the advancement of biomaterials with satisfactory bioapplications. As researchers delve deeper into the possibilities afforded by PET-RAFT polymerization, the collaborative efforts of individuals from diverse disciplines will prove invaluable in unleashing its full potential. This Review presents a concise introduction to the fundamental principles of PET-RAFT, outlines the progress in photocatalyst development, highlights its primary applications, and offers insights for future advancements in this technique, paving the way for exciting innovations and applications.

Highly Efficient Near-Infrared Photoinduced Electron/Energy Transfer-Reversible Addition–Fragmentation Chain Transfer Polymerization via the Energy Transfer Upconversion Mechanism

Near-infrared (NIR) light-mediated polymerization has been of particular interest owing to the deep penetration into opaque materials, giving rise to great potential for biomedical applications and solar photochemistry. Photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization presented unprecedented spatiotemporal control over the controlled radical polymerization process. Herein, we greatly extended the NIR region up to 980 nm by introducing rationally designed upconversion nanocrystals with low toxicity and resistance to photobleaching into PET-RAFT polymerization. Well-defined polymers with predictable molecular weight and narrow dispersity were prepared within a few hours by 980 nm NIR light-regulated PET-RAFT polymerization via the energy transfer upconversion mechanism. The livingness feature of this photopolymerization was confirmed by polymerization kinetics, chain extension experiments, and multiple controlled “on–off” light switching cycles. Furthermore, the polymerizations could be successfully performed using different monomers, in the presence of several visible light-proof barriers (i.e., pork/chicken skin) and even under aerobic conditions, demonstrating the multifold advantages of our approach.

Photoinduced Ion-Pair Inner-Sphere Electron Transfer-Reversible Addition-Fragmentation Chain Transfer Polymerization.

Photoredox-mediated reversible deactivation radical polymerization (RDRP) is a promising method of precise synthesis of polymers with diverse structures and properties. However, its mechanism mainly based on the outer-sphere electron transfer (OSET) leads to stringent requirements for an efficient photocatalyst. In this paper, the zwitterionic organoboranes [L2B]+X- are prepared and applied in reversible addition-fragmentation chain transfer (RAFT) polymerization with the photoinduced ion-pair inner-sphere electron transfer (IP-ISET) mechanism. The ion-pair electron transfer mechanism and the formation of the radical [L2B]• are supported by electron paramagnetic resonance (EPR) radical capture experiments, 1H/11B NMR spectroscopy, spectroelectrochemical spectroscopy, transient absorption spectroscopy, theoretical calculation, and photoluminescence quenching experiments. Photoluminescence quenching experiments show that when [CTA]/[[L2B]+] ≥ 0.6, it is static quenching because of the in situ formation of [L2B]+[ZCS2]-, the real catalytic species. [L2B]+[C3H7SCS2]- is synthesized, and its photoluminescence lifetime is the same as the lifetime in the static quenching experiment, indicating the formation of [L2B]+[ZCS2]- in polymerization and the IP-ISET mechanism. The matrix-assisted laser desorption ionization time-of-flight mass (MALDI-TOF MS) spectra show that the structure of [C3H7SCS2] was incorporated into the polymer, indicating that ion-pair electron transfer occurs in catalytic species. The polymerization shows high catalytic activity at ppb catalyst loading, a wide range of monomers, excellent tolerance in the presence of 5 mol % phenolic inhibitors, and the synthesis of ultrahigh-molecular-weight polymers. This protocol with the IP-ISET mechanism exhibits a value in the development of new organic transformations and polymerization methods.

Anti-UV and hydrophobic dual-functional coating fabrication for flame retardant polyester fabrics by surface-initiated PET RAFT technique

Inspired by the flourish of living radical polymerization (LRP), surface-initiated LPR technology shows great potential in good control and accurate tailoring of target polymer coatings. In this work, surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain transfer polymerization (SI-PET-RAFT) was employed as a facile synthetic rout for the fabrication of surface-tethered polymeric brushes with anti-UV and hydrophobic properties for flame retardant polyester fabrics (FRPET). Firstly, RAFT agent 4-Cyano-4-[(dodecyl sulfanyl thiocarbonyl) sulfanyl] pentanoic acid (CDTPA) was grafted onto polydopamine (PDA) deposited FRPET, followed by the controlled growth of glycidyl methacrylate (GMA) onto polyester fabrics via SI-PET-RAFT method. Finally, benzotriazole anti-UV agents were grafted as secondary functionalization. According to SEM-EDS and XPS analysis, PGMA has been immobilized successfully onto the surface of FRPET fabrics. An efficient PET RAFT polymerization of GMA with low dispersity (Ð<1.2), temporal control, and chain-end fidelity was achieved under mild yellow light irradiation (λmax = 570 nm, 4 W/m2). It also exhibited the feasibility of polymerization under natural sunlight and oxygen tolerance. The flame retardant, UV resistant and hydrophobic properties of the treated fabrics were investigated. In the microscale combustion calorimetry test, the peak heat release rate (PHRR) effectively decreased by 59.50%. In the cone calorimetry test, the PHRR and total heat release also reduced. The melt-dripping was eliminated in the vertical flaming test and reached V-0 rating with LOI value of 28%. The UV transmittance of the fabric decreased to<4%, meeting the standard of UV resistant fabric and the water contact angle reached 125°, thus making flame retardant polyester fabric have good hydrophobicity. Besides, it also kept good durability in flame retardancy, UV shielding and water repellent. This study provides new insights into the surface engineering of photoregulated LRP techniques for multi-functional coating synthesis.

Synthesis of Polymer Brushes Via SI-PET-RAFT for Photodynamic Inactivation of Bacteria.

Biofilms are a persistent issue in healthcare and industry. Once formed, the eradication of biofilms is challenging as the extracellular polymeric matrix provides protection against harsh environmental conditions and physically enhances resistance to antimicrobials. The fabrication of polymer brush coatings provides a versatile approach to modify the surface to resist the formation of biofilms. Herein, the authors report a facile synthetic route for the preparation of surface-tethered polymeric brushes with antifouling and visible light activated bactericidal properties using surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain transfer polymerization (SI-PET-RAFT). Bactericidal property via the generation of singlet oxygen, which can be temporally and spatially controlled, is investigated against both Gram-positive and Gram-negative bacteria. In addition, the antibacterial properties of the surface can be recycled. This work paves the way for the preparation of polymer films that can resist and kill bacterial biofilms.

Benchtop Preparation of Polymer Brushes by SI-PET-RAFT: The Effect of the Polymer Composition and Structure on Inhibition of a Pseudomonas Biofilm

We report a high-throughput method for producing surface-tethered polymeric brushes on glass substrates via surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain transfer polymerization (SI-PET-RAFT). Due to its excellent oxygen tolerance, SI-PET-RAFT allows brush growth using low reagent volumes (30 μL) without prior degassing. An initial 28 homopolymer brush library was successfully prepared and screened with respect to their antifouling performance. The high-throughput approach was further exploited to expand the library to encompass statistical, gradient, and block architectures to investigate the effect of monomer composition and distribution using two monomers of disparate performance. In this manner, the degree of attachment from Gram-negative Pseudomonas aeruginosa (PA) bacterial biofilms could be tuned between the bounds set by the homopolymer brushes.

Effect of Hydrophobic Groups on Antimicrobial and Hemolytic Activity: Developing a Predictive Tool for Ternary Antimicrobial Polymers.

Antimicrobial polymers have emerged as a potential solution to the growing problem of antimicrobial resistance. Although several studies have examined the effects of various parameters on the antimicrobial and hemolytic activity of statistical copolymers, there are still numerous parameters to be explored. Therefore, in this study, we developed a library of 36 statistical amphiphilic ternary copolymers prepared via photoinduced electron transfer-reversible addition-fragmentation chain transfer polymerization to systematically evaluate the influence of hydrophobic groups [number of carbons (5, 7, and 9)] and chain type of the hydrophobic monomer (cyclic, aromatic, linear, or branched), monomer ratio, and degree of polymerization (DPn) on antimicrobial and hemolytic activity. To guide our synthetic strategy, we developed a pre-experimental screening approach using C log P values of oligomer models, which correspond to the logarithm of the partition coefficient of compounds between n-octanol and water. This method enabled correlation of polymer hydrophobicity with antimicrobial and hemolytic activity. In addition, this study revealed that minimizing hydrophobicity and hydrophobic content were key factors in controlling hemolysis, whereas optimizing antimicrobial activity was more complex. High antimicrobial activity required hydrophobicity (i.e., C log P, hydrophobicity index) that was neither too high nor too low, an appropriate cationic/hydrophobic balance, and structural compatibility between the chosen monomers. Furthermore, these findings could guide the design of future antimicrobial ternary copolymers and suggest that C log P values between 0 and 2 have the best balance of high antimicrobial activity and low hemolytic activity.

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.

Polymerization-Induced Self-Assembly Using Visible Light Mediated Photoinduced Electron Transfer-Reversible Addition-Fragmentation Chain Transfer Polymerization.

The ruthenium-based photoredox catalyst, Ru(bpy)3Cl2, was employed to activate reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization via a photoinduced electron transfer (PET) process under visible light (λ = 460 nm, 0.7 mW/cm2). Poly(oligo(ethylene glycol) methyl ether methacrylate) was chain extended with benzyl methacrylate to afford in situ self-assembled polymeric nanoparticles with various morphologies. The effect of different intrinsic reaction parameters, such as catalyst concentration, total solids content, and cosolvent addition was investigated with respect to the formation of different nanoparticle morphologies, including spherical micelles, worm-like micelles, and vesicles. Importantly, highly pure worm-like micelles were readily isolated due to the in situ formation of highly viscous gels. Finally, "ON/OFF" control over the dispersion polymerization was demonstrated by online Fourier transform near-infrared (FTNIR) spectroscopy, allowing for temporal control over the nanoparticle morphology.