A Robust and Versatile Photoinduced Living Polymerization of Conjugated and Unconjugated Monomers and Its Oxygen Tolerance

Abstract

Controlled/living radical polymerization techniques have transformed polymer chemistry in the last few decades, affording the production of polymers with precise control over both molecular weights and architectures. It is now possible to synthesize almost an infinite variety of macromolecules using nonspecialized equipment, finding applications in high-tech industry. However, they have several shortcomings. Until recently, living radical polymerizations could not be controlled by an external stimulus, such as visible light, pH, mechanical, chemical, etc. Moreover, they are usually sensitive to trace amounts of oxygen in the system. In this Article, we report a photoinduced living polymerization technique, which is able to polymerize a large range of monomers, including conjugated and unconjugated monomers, using ultralow concentrations of an iridium-based photoredox catalyst (typically 1 ppm to monomers) and a low energy visible LED as the light source (1-4.8 W, λ(max) = 435 nm). The synthesis of homopolymers with molecular weights ranging from 1000 to 2,000,000 g/mol was successfully achieved with narrow molecular weight distributions (M(w)/M(n) < 1.3). In addition, chain extensions of poly(methacrylate)s, poly(styrene), poly(N-vinyl pyrrolidinone), poly(vinyl ester)s, and poly(acrylate)s were performed to prepare diblock copolymers. The reusability of the catalyst was demonstrated by the synthesis of a decablock polymer by multiple chain extensions. Most importantly, this process was employed to prepare well-defined polymers and multiblock copolymers in the presence of air.

Mn2(CO)10-photomediated synthesis of poly(vinylidene fluoride)-b-poly(styrene sulfonate)

“…Other examples of photo enabled CRPs of other monomers have also recently been reported [57,58]. Moreover, we have also shown that while the concentration of PVDFACH 2 ACF 2 AI chain end decreases and that of PVDFACF 2 ACH 2 AI chain end increases with conversion, their sum, the total iodine chain end functionality, remains relatively constant, and >90%, a value suitable for block copolymer synthesis.…”

Visible light sensitive photoinitiating systems: Recent progress in cationic and radical photopolymerization reactions under soft conditions

“…Recently, many new photoinitiating systems for controlled polymerization with visible light, and even sunlight, have been reported (see Table 13) [20,21,[246][247][248][249][250][251][252][253][254][255]. These systems are mainly based on the photoinduced ATRP and/or the photoredox catalysis approach [20,21,[248][249][250][251][252][253][254][255].…”

“…These systems are mainly based on the photoinduced ATRP and/or the photoredox catalysis approach [20,21,[248][249][250][251][252][253][254][255]. The use of Cu or Ir catalysts has been found particularly appropriate, i.e., these compounds exhibit excellent visible light absorption properties.…”

Visible light‐induced thiol‐ene reaction: A new strategy to prepare Α,ω‐dithiol and Α,ω‐divinyl telechelic polythiolether oligomers

“…24 In addition, Xu and coworkers reported a new photoinduced living polymerization involving an electron transfer process between fac-Ir(ppy) 3 and the thiocarbonylthio compound and a cooperative RAFT process that would be able to polymerize a large range of monomers, even in the presence of oxygen. 25,26 Futhermore, the facIr(ppy) 3 catalyst has also been exploited in the surface grafting polymerization [27][28][29] and post-functionalization of polymers. 29,30 As a summary, fac-Ir(ppy) 3 has been successfully used in organic chemistry, polymer modification and materials science without the addition of sacrifice reductants.…”