Visible Light Induced RAFT Polymerization of 2-Vinylpyridine without Exogenous Initiators or Photocatalysts

Photo-Iniferter RAFT Polymerization

Light-mediated polymerization techniques offer distinct advantages over polymerization reactions fueled by thermal energy, such as high spatial and temporal control as well as the possibility to work under mild reaction conditions. Reversible addition-fragmentation chain-transfer (RAFT) polymerization is a highly versatile radical polymerization method that can be utilized to control a variety of monomers and produce a vast number of complex macromolecular structures. The use of light to drive a RAFT-polymerization is possible via multiple routes. Besides the use of photo-initiators, or photo-catalysts, the direct activation of the chain transfer agent controlling the RAFT process in a photo-iniferter (PI) process is an elegant way to initiate and control polymerization reactions. Within this review, PI-RAFT polymerization and its advantages over the conventional RAFT process are discussed in detail.

Photoregulated reversible addition–fragmentation chain transfer (RAFT) polymerization

Different strategies on photoregulated RAFT polymerization are developed. This minireview summarizes recent advances in photoregulated RAFT polymerization and its applications.

Catalyst free removal of trithiocarbonate RAFT CTAs from poly(vinylpyridine)s using tris(trimethylsilyl)silane and light

Trithiocarbonate end groups on various polymers, including polyvinylpyridines, are reduced rapily and quantitatively using only tris(trimethylsilyl)silane and light.

Synthesis of Poly(3-vinylpyridine)-Block-Polystyrene Diblock Copolymers via Surfactant-Free RAFT Emulsion Polymerization

In this work, we present a novel synthetic route to diblock copolymers based on styrene and 3-vinylpyridine monomers. Surfactant-free water-based reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of styrene in the presence of the macroRAFT agent poly(3-vinylpyridine) (P3VP) is used to synthesize diblock copolymers with molecular weights of around 60 kDa. The proposed mechanism for the poly(3-vinylpyridine)-block-poly(styrene) (P3VP-b-PS) synthesis is the polymerization-induced self-assembly (PISA) which involves the in situ formation of well-defined micellar nanoscale objects consisting of a PS core and a stabilizing P3VP macroRAFT agent corona. The presented approach shows a well-controlled RAFT polymerization, allowing for the synthesis of diblock copolymers with high monomer conversion. The obtained diblock copolymers display microphase-separated structures according to their composition.

Ultra-fast aqueous polymerisation of acrylamides by high power visible light direct photoactivation RAFT polymerisation

The effect of visible LED power (λ_max= 402 nm, 451 nm) on kinetics and control of direct photoactivation RAFT polymerisations of acrylamide and dimethylacrylamide are investigated.

Photoinduced controlled radical polymerization of methyl acrylate and vinyl acetate by xanthate

A block copolymer of PMA-b-PVAc was successfully synthesized using photo-induced RAFT polymerization with a xanthate.

Thermal and photo-RAFT polymerization of 2,2,2-trifluoroethyl α-fluoroacrylate

RAFT polymerization of 2,2,2-trifluoroethyl α-fluoroacrylate (FATRIFE) was studied under thermal conditions and light irradiation in the presence of four chain transfer agents. Polymers with narrow dispersities were obtained in the presence of trithiocarbonate CTA₂, and this further led to fluorinated block copolymers.

Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA): New Insights and Opportunities

The polymerization-induced self-assembly (PISA) process is a useful synthetic tool for the efficient synthesis of polymeric nanoparticles of different morphologies. Recently, studies on visible light initiated PISA processes have offered a number of key research opportunities that are not readily accessible using traditional thermally initiated systems. For example, visible light mediated PISA (Photo-PISA) enables a high degree of control over the dispersion polymerization process by manipulation of the wavelength and intensity of incident light. In some cases, the final nanoparticle morphology of a single formulation can be modulated by simple manipulation of these externally controlled parameters. In addition, temporal (and in principle spatial) control over the Photo-PISA process can be achieved in most cases. Exploitation of the mild room temperature polymerizations conditions can enable the encapsulation of thermally sensitive therapeutics to occur without compromising the polymerization rate and their activities. Finally, the Photo-PISA process can enable further mechanistic insights into the morphological evolution of nanoparticle formation such as the effects of temperature on the self-assembly process. The purpose of this mini-review is therefore to examine some of these recent advances that have been made in Photo-PISA processes, particularly in light of the specific advantages that may exist in comparison with conventional thermally initiated systems.

Assembly of a visible light photoreactor: an inexpensive tool for bottlebrush polymer synthesis via photoiniferter polymerization

We report the design of a simple, inexpensive photoreactor for photoiniferter polymerization of vinyl monomers mediated by thiocarbonylthio compounds. This photoreactor allowed for the synthesis of block copolymers and well-defined bottlebrush polymers by grafting-from and grafting-through.

Investigation into the mechanism of photo-mediated RAFT polymerization involving the reversible photolysis of the chain-transfer agent

A new dithiocarbamate with a N-carbazole Z group is synthesized and investigated as a chain-transfer agent (CTA) in a photo-mediated RAFT polymerization mechanism involving its partial and reversible photolysis.

RAFT iniferter polymerization in miniemulsion using visible light

Methodology for the successful implementation of RAFT (4-cyano-4[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid (CDTPA)) iniferter polymerization of butyl methacrylate in miniemulsion using visible light (green light; λ_max = 530 nm) has been developed.