Metal‐Free Atom Transfer Radical Polymerization of Methyl Methacrylate with ppm Level of Organic Photocatalyst

Abstract

It is well known that the recently developed photoinduced metal-free atom transfer radical polymerization (ATRP) has been considered as a promising methodology to completely eliminate transition metal residue in polymers. However, a serious problem needs to be improved, namely, large amount of organic photocatalysts should be used to keep the controllability over molecular weights and molecular weight distributions. In this work, a novel photocatalyst 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) with strong excited state reduction potential is successfully used to mediate a metal-free ATRP of methyl methacrylate just with parts per million (ppm) level usage under irradiation of blue light emitting diode at room temperature, using ethyl α-bromophenyl-acetate as a typical initiator with high initiator efficiency. The polymerization kinetic study, multiple controlled "on-off" light switching cycle regulation, and chain extension experiment confirm the "living"/controlled features of this promising photoinduced metal-free ATRP system with good molecular weight control in the presence of ppm level photocatalyst 4CzIPN.

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

“…Two seminal works in 2014 reported by Hawker and co‐workers [ 44 ] and Miyake and Theriot [ 45 ] opened the field of metal‐free ATRP as both 10‐phenylphenothiazine (Ph‐PTH) and perylene were successfully applied as photoredox catalysts for controlled polymerization of methacrylates, acrylates, acrylonitrile, styrene, and so on. [ 46,47 ] Various photoredox catalysts, including derivatives of phenothiazine, perylene, phenazine, [ 48 ] phenoxazine, [ 49 ] fluorescein, [ 50,51 ] carbazole, [ 52 ] and thienothiophene [ 53 ] photocatalysts, were subsequently developed, resulting in flourishing research of photomediated CRPs. [ 54–58 ]…”

“…There is a strong interest to develop alternative and "greener" methods by avoiding the use of copper in ATRP.Two seminal works in 2014 reported by Hawker and coworkers [44] and Miyake and Theriot [45] opened the field of metalfree ATRP as both 10-phenylphenothiazine (Ph-PTH) and perylene were successfully applied as photoredox catalysts for controlled polymerization of methacrylates, acrylates, acrylonitrile, styrene, and so on. [46,47] Various photoredox catalysts, including derivatives of phenothiazine, perylene, phenazine, [48] phenoxazine, [49] fluorescein, [50,51] carbazole, [52] and thienothiophene [53] photocatalysts, were subsequently developed, resulting in flourishing research of photomediated CRPs. [54][55][56][57][58] Since the first discovery in 1995, ATRP has been conducted successfully in various dispersed media, including suspension, emulsion, seeded emulsion, miniemulsion, microemulsion, Atom transfer radical polymerization (ATRP), as one of the most successful controlled radical polymerization techniques, has been broadly used by polymer chemists and nonspecialists for synthesis of various functional materials, although the use of copper as traditional catalyst often results in undesired color or properties.…”

Photoinduced Organocatalyzed Atom Transfer Radical Polymerization Using Continuous Flow

“…Significant advancements have enabled the use of lower levels of transition metal catalysts 10–13 and increased ability for polymer purification, 14–16 while recently organocatalyzed ATRP (O-ATRP) has risen as an approach to entirely eliminate metal contamination of the polymer product. 17–22 …”

Photo‐Controlled Polymerization‐Induced Self‐Assembly (Photo‐PISA): A Novel Strategy Using In Situ Bromine‐Iodine Transformation Living Radical Polymerization

“…Among all kinds of light sources, light emitting diode (LED) light is a facile and fascinating choice for the synthesis of well‐defined polymers through the LRP process because of its unique character, such as easy operation, economic factors, and low energy consumption. More importantly, it is harmless to humans . In this work, attention was focused on developing a PISA process in bromine‐iodine transformation LRP using a blue LED light.…”