Ambient Temperature “Flash” SARA ATRP of Methyl Acrylate in Water/Ionic Liquid/Glycol Mixtures

Toward Green Atom Transfer Radical Polymerization: Current Status and Future Challenges

Reversible-deactivation radical polymerizations (RDRPs) have revolutionized synthetic polymer chemistry. Nowadays, RDRPs facilitate design and preparation of materials with controlled architecture, composition, and functionality. Atom transfer radical polymerization (ATRP) has evolved beyond traditional polymer field, enabling synthesis of organic-inorganic hybrids, bioconjugates, advanced polymers for electronics, energy, and environmentally relevant polymeric materials for broad applications in various fields. This review focuses on the relation between ATRP technology and the 12 principles of green chemistry, which are paramount guidelines in sustainable research and implementation. The green features of ATRP are presented, discussing the environmental and/or health issues and the challenges that remain to be overcome. Key discoveries and recent developments in green ATRP are highlighted, while providing a perspective for future opportunities in this area.

Organocatalyzed atom transfer radical polymerization (ATRP) using triarylsulfonium hexafluorophosphate salt (THS) as a photocatalyst

Triarylsulfonium hexafluorophosphate salt (THS), an organic and inexpensive compound, was employed as a photocatalyst for metal free atom transfer radical polymerization (ATRP) of methacrylate monomers.

Liquid salts as eco-friendly solvents for atom transfer radical polymerization: a review

Liquid salts, comprising ionic liquids and eutectic mixtures, are organic compounds/mixtures characterized by a low melting point that have been emerging as a very promising eco-friendly solvent for atom transfer radical polymerization.

Ligand-free iron-based electrochemically mediated atom transfer radical polymerization of methyl methacrylate

This article reports the iron-catalyzed ligand-free eATRP.

Addressing the role of triphenylphosphine in copper catalyzed ATRP

A new Atom Transfer Radical Polymerization (ATRP) process with triphenylphosphine (PPh₃) and [Cu^IIMe₆TREN]²⁺ as the catalyst system is reported.

Externally controlled atom transfer radical polymerization

ATRP can be externally controlled by electrical current, light, mechanical forces and various chemical reducing agents. The mechanistic aspects and preparation of polymers with complex functional architectures and their applications are critically reviewed.

Mechanism of Supplemental Activator and Reducing Agent Atom Transfer Radical Polymerization Mediated by Inorganic Sulfites: Experimental Measurements and Kinetic Simulations

The mechanism of atom transfer radical polymerization (ATRP) mediated by sodium dithionite (Na2S2O4), with CuIIBr2/Me6TREN as catalyst (Me6TREN: tris[2-(dimethylamino)ethyl]amine)) in ethanol/water mixtures, was investigated experimentally and by kinetic simulations. A kinetic model was proposed and the rate coefficients of the relevant reactions were measured. The kinetic model was validated by the agreement between experimental and simulated results. The results indicated that the polymerization followed the SARA ATRP mechanism, with a SO2•- radical anion derived from Na2S2O4, acting as both supplemental activator (SA) of alkyl halides and reducing agent (RA) for CuII/L to regenerate the main activator CuI/L. This is similar to the reversible-deactivation radical polymerization (RDRP) procedure conducted in the presence of Cu0. The electron transfer from SO2•-, to either CuIIBr2/Me6TREN or R-Br initiator, appears to follow an outer sphere electron transfer (OSET) process. The developed kinetic model was used to study the influence of targeted degree of polymerization, concentration of CuIIBr2/Me6TREN and solubility of Na2S2O4 on the level of polymerization control. The presence of small amounts of water in the polymerization mixtures slightly increased the reactivity of the CuI/L complex, but markedly increased the reactivity of sulfites.

Aqueous SARA ATRP using Inorganic Sulfites

Aqueous supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) using inorganic sulfites was successfully carried out for the first time. Under optimized conditions, a well-controlled poly[oligo(ethylene oxide) methyl ether acrylate] (POEOA) was obtained with <30 ppm of soluble copper catalyst using tris(2-pyridylmethyl)amine (TPMA) ligand in the presence of an excess of halide salts (e.g. NaCl). Inorganic sulfites (e.g. Na2S2O4) were continuously fed into the reaction mixture. The mechanistic studies proved that these salts can activate alkyl halides directly and regenerate the activator complex. The effects of the feeding rate of the SARA agent (inorganic sulfites), ligand and its concentration, halide salt and its concentration, sulfite used, and copper concentration, were systematically studied to afford fast polymerizations rates while maintaining the control over polymerization. The kinetic data showed linear first-order kinetics, linear evolution of molecular weights with conversion, and polymers with narrow molecular weight distributions (Đ ~1.2) during polymerization even at relatively high monomer conversions (~80%). "One-pot" chain extension and "one-pot" block copolymerization experiments proved the high chain-end functionality. The polymerization could be directly regulated by starting or stopping the continuous feeding of the SARA agent. Under biologically relevant conditions, the aqueous SARA ATRP using inorganic sulfites was used to synthesize a well-defined protein-polymer hybrid by grafting of P(OEOA480) from BSA-O-[iBBr]30.

Trithiocarbonates as intrinsic photoredox catalysts and RAFT agents for oxygen tolerant controlled radical polymerization

In this study, we reported on the discovery that trithiocarbonates (RAFT agents) can act as intrinsic photocatalyst to significantly reduce the oxygen level in a controlled radical polymerization under visible light irridation.

Deep eutectic solvents for green and efficient iron-mediated ligand-free atom transfer radical polymerization

This article reports the iron-catalyzed ligand-free ATRP with DES as a green additive.

Biosynthetic Polymers as Functional Materials

The synthesis of functional polymers encoded with biomolecules has been an extensive area of research for decades. As such, a diverse toolbox of polymerization techniques and bioconjugation methods has been developed. The greatest impact of this work has been in biomedicine and biotechnology, where fully synthetic and naturally derived biomolecules are used cooperatively. Despite significant improvements in biocompatible and functionally diverse polymers, our success in the field is constrained by recognized limitations in polymer architecture control, structural dynamics, and biostabilization. This Perspective discusses the current status of functional biosynthetic polymers and highlights innovative strategies reported within the past five years that have made great strides in overcoming the aforementioned barriers.

Cyclopentyl methyl ether as a green solvent for reversible-addition fragmentation chain transfer and nitroxide-mediated polymerizations

Cyclopentyl methyl ether (CPME) was successfully used as an environmentally friendly alternative to regularly employed organic solvents (e.g., THF, DMSO, DCM and DMF) for the RAFT and NMP polymerizations of vinyl chloride (VC) and styrene (S).