Photocontrolled Iodine-Mediated Green Reversible-Deactivation Radical Polymerization of Methacrylates: Effect of Water in the Polymerization System

Expanding monomer scope and enabling post-modification in photocontrolled radical ring-opening polymerization of vinylcyclopropanes by an iodine transfer strategy

Visible light-driven iodine transfer polymerization provides efficient and unique access to novel poly(vinylcyclopropanes) with enhanced material properties.

Photoinduced organocatalyzed controlled radical polymerization feasible over a wide range of wavelengths

We successfully synthesized a catalyst with a wide absorption range (300–1000 nm) for controlled radical polymerization of PEGMA in aqueous solution and MMA in bulk under the irradiation of white, blue, green, red, and NIR LED light, and sunlight.

Preparation of core–shell nanoparticles via emulsion polymerization induced self-assembly using a maleamic acid-α-methyl styrene copolymer as a macro-initisurf

An amphiphilic maleamic acid-α-methyl styrene copolymer (macro-initisurf) acting as a macroinitiator and emulsifier for the emulsion polymerization induced self-assembly of acrylate monomers to prepare core–shell nanoparticles.

Synthesis of micrometer-sized poly(vinyl acetate) particles through microsuspension iodine transfer polymerization: effect of iodine species in a water medium

Schematic of the behaviors of iodine species in the microsuspension polymerization of vinyl acetate (VAc) in an aqueous medium.

Preparation of Emulsifier-Free Styrene-Acrylic Emulsion via Reverse Iodine Transfer Polymerization

Styrene-acrylic emulsions containing hydroxyl functional monomer unit's component are widely used for maintenance coating. In this paper, a stable emulsifier-free styrene-acrylic emulsion with solid content over 43% could be obtained in 210 min via reverse iodine transfer polymerization (RITP). By adding a mixture of methacrylic acid (MAA) and poly(ethylene glycol)methyl ether methacrylate (PEGMA) into a system containing a high content of hydroxyl functional monomer component (19.4 wt.% of the total monomer mass), styrene (St) could be copolymerized with methyl methacrylate (MMA); the modified film exhibited good hardness properties, good adhesive properties, and low water absorption. An increase in the amount of PEGMA decreased the glass transition temperature (Tg). When 1.4 times the reference amount of initiator was added, the highest molecular weight Mn could reach 40,000 g.·mol-1 with 0.25 times the reference amount of iodine in the emulsion. The largest tensile strength of the dried emulsion film over 5.5 MPa endowed the material with good mechanical properties. Living polymerization was proven by the kinetics of RITP emulsion and chain extension reaction. TEM micrographs manifest the emulsification of the seed random copolymer. This paper may provide a potential methodology for preparing polymer materials with excellent mechanical properties.

Facile Synthesis of Unimodal Polymethacrylates with Narrow Dispersity via NIR LED Light-Controlled Bromine-Iodine Transformation Reversible-Deactivation Radical Polymerization

A facile and clean strategy for synthesizing unimodal polymethacrylates with narrow dispersity (Đ < 1.10) is successfully developed by a near-infrared (NIR) light-emitting diode (LED) light (λ_max = 740 nm)-controlled in situ bromine-iodine transformation reversible-deactivation radical polymerization system without the use of NIR dyes and expensive catalysts. In this system, alkyl iodide ethyl α-iodophenylacetate (EIPA) initiator is generated in situ by the nucleophilic substitution reaction between an alkyl bromide compound ethyl α-bromophenylacetate and sodium iodide (NaI). At the same time, excessive NaI is also acted as a highly active catalyst by forming halogen bonds with terminal iodine of the polymer chains in this system to make it capable of precisely synthesizing polymethacrylates with narrow dispersities (Đ = 1.03-1.10). In addition, the strong penetration ability of NIR LED light is illustrated by the successful polymerization even through 11 pieces of A4 paper.

Synthesis of Micrometer-Sized Poly(methyl acrylate) by Temperature-Step Microsuspension Polymerization with Iodoform Based on the "Radical Exit Depression" Effect§

Previously, we have reported the successful preparation of micrometer-sized poly(methyl methacrylate) particles without submicrometer-sized byproduct particles by microsuspension iodine-transfer polymerization (ms ITP), in which the radical exit depression (RED) effect was expected, with the benzoyl peroxide initiator at 8 wt % relative to the monomer. However, it was difficult to apply it simply under a similar condition for methyl acrylate (MA), which is more hydrophilic than methyl methacrylate (MMA), because the polymerization rate in the water phase (R_p^w) arising from the oligomer radicals exiting from the monomer droplets is high, resulting in a lot of submicrometer-sized byproduct particles. In this study, the problem was overcome by utilizing a two-step temperature process in the microsuspension polymerization with iodoform (ms I) of MA, which supports the proposed mechanism in the ms ITP of MMA in the previous paper. Although the control of the molecular weight (M_n) and the molecular weight distribution (M_n/M_w) was restricted, the preparation of micrometer-sized particles without byproduct particles was realized and a high conversion was reached within a practical time that meets the demands of the industry by utilizing the ms I. The optimal conditions for MA were 70 °C for 2 h, followed by 80 °C for 4 h with a high content of initiator (8 wt % relative to a monomer).

Photocontrolled bromine–iodine transformation reversible-deactivation radical polymerization: facile synthesis of star copolymers and unimolecular micelles

A facile strategy of synthesizing star copolymers was successfully established via photocontrolled BIT-RDRP. The obtained copolymers have well-defined four-arm amphiphilic block architecture and can form stable unimolecular micelles in water.

Photocontrolled Iodine-Mediated Reversible-Deactivation Radical Polymerization: Solution Polymerization of Methacrylates by Irradiation with NIR LED Light

Herein, near-infrared (NIR) photocontrolled iodide-mediated reversible-deactivation radical polymerization (RDRP) of methacrylates, without an external photocatalyst, was developed using an alkyl iodide (e.g., 2-iodo-2-methylpropionitrile) as the initiator at room temperature. This example is the first use of a series of special solvents containing carbonyl groups (e.g., 1,3-dimethyl-2-imidazolidinone) as both solvent and catalyst for photocontrolled RDRP using long-wavelength (λ_max =730 nm) irradiation. The polymerization system comprises monomer, alkyl iodide initiator, and solvent. Well-defined polymers were synthesized with excellent control over the molecular weights and molecular weight distributions (M_w /M_n <1.21). The living features of this system were confirmed by polymerization kinetics, multiple controlled "on-off" light switching cycles, and chain extension experiments. Importantly, the polymerizations proceeded successfully with various barriers (pork skin and A4 paper), demonstrating the advantage of high-penetration NIR light.

One-Step Photocontrolled Polymerization-Induced Self-Assembly (Photo-PISA) by Using In Situ Bromine-Iodine Transformation Reversible-Deactivation Radical Polymerization

Polymerization-induced self-assembly (PISA) has become an effective strategy to synthesize high solid content polymeric nanoparticles with various morphologies in situ. In this work, one-step PISA was achieved by in situ photocontrolled bromine-iodine transformation reversible-deactivation radical polymerization (hereinafter referred to as Photo-BIT-RDRP). The water-soluble macroinitiator precursor α-bromophenylacetate polyethylene glycol monomethyl ether ester (mPEG1k-BPA) was synthesized in advance, and then the polymer nanomicelles (mPEG1k-b-PBnMA and mPEG1k-b-PHPMA, where BnMA means benzyl methacrylate and HPMA is hydroxypropyl methacrylate) were successfully formed from a PISA process of hydrophobic monomer of BnMA or HPMA under irradiation with blue LED light at room temperature. In addition, the typical living features of the photocontrolled PISA process were confirmed by the linear increase of molecular weights of the resultant amphiphilic block copolymers with monomer conversions and narrow molecular weight distributions (Mw/Mn < 1.20). Importantly, the photocontrolled PISA process is realized by only one-step method by using in situ photo-BIT-RDRP, which avoids the use of transition metal catalysts in the traditional ATRP system, and simplifies the synthesis steps of nanomicelles. This strategy provides a promising pathway to solve the problem of active chain end (C-I) functionality loss in two-step polymerization of BIT-RDRP.

Synthesis of nano-capsules via aqueous emulsion RCMP-PISA and encapsulation

Synthesis of nano-capsules using aqueous RCMP-PISA and encapsulation of rhodamine-B (Rh-B).

Iodine-mediated photoATRP in aqueous media with oxygen tolerance

Iodine-mediated photoATRP was conducted in aqueous media enabling fast and well-controlled polymerizations under visible light without deoxygenation.

Photocontrolled iodine-mediated reversible-deactivation radical polymerization with a semifluorinated alternating copolymer as the macroinitiator

A novel strategy for preparing block copolymers with semifluorinated alternating copolymers as macroinitiators was established by photocontrolled iodine-mediated RDRP under irradiation with blue LED light at room temperature.

Facile synthesis of poly(N-vinyl pyrrolidone) block copolymers with “more-activated” monomers by using photoinduced successive RAFT polymerization

Well-defined PNVP block copolymers with more-activated monomers were synthesized by a single RAFT polymerization method under irradiation with visible light at room temperature.

Iodine-mediated photo-controlled atom transfer radical polymerization (photo-ATRP) and block polymerization combined with ring-opening polymerization (ROP) via a superbase

Most organocatalysts for photo-controlled atom transfer radical polymerization (photo-ATRP) are metal complexes or synthetically elaborate organic dyes, which are toxic and expensive.

Recent development in halogen-bonding-catalyzed living radical polymerization

The development and applications of an organocatalyzed living radical polymerization via halogen-bonding catalysis, i.e., reversible complexation mediated polymerization (RCMP), are highlighted.

Cationic quaternary ammonium salt-catalyzed LED-induced living radical polymerization within situhalogen exchange

Cationic quaternary ammonium salts were employed as organocatalysts for light-emitting diode (LED)-induced living radical polymerization (LRP) with thein situhalogen exchange of methacrylate monomers.