Visible-Light-Controlled Living Radical Polymerization from a Trithiocarbonate Iniferter Mediated by an Organic Photoredox Catalyst

Abstract

Living radical polymerization of acrylates and acrylamides from trithiocarbonate iniferters using a compact fluorescent lamp (CFL) bulb and 10-phenylphenothiazine as an organic photoredox catalyst is reported. With this system, chain growth can be efficiently switched between “on” and “off” in response to visible light. Polymer molar masses increase linearly with conversion, and narrow molar mass distributions are obtained. The excellent fidelity of the trithiocarbonate-iniferter enables the preparation of triblock copolymers from macro-iniferters under the same visible-light mediated protocol, using UV light without a photoredox catalyst or under traditional thermally induced RAFT conditions. We expect that the simplicity and efficiency of this metal-free, visible-light-mediated polymerization will enable the synthesis and modification of a range of materials under mild conditions.

Synthesis of Hyperbranched Polymers via Metal‐Free ATRP in Solution and Microemulsion

“…In contrast, the metal‐free ATRP of inimer 1 in microemulsion produced latex particles with small size and monomodal size distribution with complete conversion of inimer 1 in 2 h. This result was not very surprising because there is so far no literature report of metal‐free ATRP of acrylate monomers by using activated alkyl bromides as initiator and phenothiazine as photocatalyst, although the phenothiazine‐photocatalyzed polymerizations of acrylate monomers using trithiocarbonate iniferters and arylsulfonyl halide initiators have been recently reported. [ 71,72 ] Therefore, further exploration in this study only focused on the metal‐free ATRP of methacrylate‐based inimer 1 in microemulsion to investigate the effect of several experimental parameters on the hyperbranched structures.…”

Coding and decoding libraries of sequence-defined functional copolymers synthesized via photoligation

“…Generating an ensemble of perfectly sequence-defined identical macromolecules containing exactly the same chemical information at the molecular scale—in contrast to existing avenues to disperse and irregularly coded species when compared with natural analogues—via a simple process constitutes a key technological gate for data storage, biological and material applications, yet requires reaction concepts that provide perfect yields and orthogonality under equimolar reaction conditions. Although solid-state peptide synthesis was introduced by Merrifield6—the first example of a true synthetic sequence-defined peptide—macromolecular chemists have initially focused on and developed a diverse number of solution-based polymerization strategies for imparting a certain level of control over statistical polymerization processes and exploited these for controlling the order of the building blocks (sequence-controlled polymers)7891011121314151617181920. In addition, the advent of modular synthetic strategies21222324 has contributed significantly towards achieving a high level of control over macromolecular formation processes.…”

Organocatalyzed Atom Transfer Radical Polymerization Using N-Aryl Phenoxazines as Photoredox Catalysts

“…2 Concerns about metal contamination of polymers intended for biomedical or electronic applications have motivated efforts to lower metal catalyst loadings and enhance purification methods. 3 Although CRPs exist that are mediated by organic catalysts and which thus entirely circumvent the issue of metal contamination, 4 organic catalysts capable of mediating an organocatalyzed ATRP (O-ATRP) are limited because of the required significant reducing power required to reduce alkyl bromides commonly used for ATRP (∼ −0.6 to −0.8 V vs SCE). 5 …”