A new photoinitiating system involving electron acceptor dyes, namely, eosin Y and erythrosin B, in conjunction with alkyl halides and amines for photoinduced ATRP of (meth)acrylates and vinyl monomers in the absence of inorganic catalysts is reported.

Photoinduced copper(I)-catalyzed Huisgen 1,3dipolar cycloaddition (CuAAC) via photoinduced electron transfer using free radical photoinitiators has been developed as a new platform to serve as orthogonal click system. Photoinitiators acting at near UV and visible range, namely 2, 2dimethoxy-2-phenyl acetophenone, 2-benzyl-2-dimethylamino-4′morpholino butyrophenone, 2,4,6-trimethylbenzoyl)diphenylphosphine oxide, dicyclopentadienyl bis[2,6-difluoro-3-(1-pyrrolyl)phenyl] titanium) and camphorquinone/benzyl alcohol were tested with copper(II) chloride/N,N,N′,N″,N″-pentamethyldiethylenetriamine complex to catalyze the CuAAC via photoinduced electron transfer reaction. This strategy has been applied in construction of various macromolecular architectures including telechelic polymers and block copolymers. Spectroscopic and chromatographic investigations revealed that successful macromolecular syntheses have been achieved by this technique.

Two thioxanthone derivatives with fluorene additional chromophoric groups, namely thioxanthone-fluorenecarboxylic acid (TX-FLCOOH) and thioxanthone-fluorene sodium carboxylate (TX-FLCOONa), as visible light absorbing oil-and water-soluble photoinitiators, respectively, were synthesized and characterized. Their ability to initiate photopolymerization of methyl methacrylate (MMA), 2-(2-phosphonoethoxymethyl)acrylic acid ethyl ester (EAEPA), and a multifunctional monomer, trimethylolpropane triacrylate (TMPTA), were examined. The initiation efficiency of TX-FLCOOH was compared with the parent thioxantone (TX) both in the presence and in the absence of a co-initiator, and TX-FLCOOH was found to be more effective in all cases. Photopolymerization and laser flash photolysis studies revealed that depending on the concentration initiation by TX-FLCOOH occurs by intra-and intermolecular H-abstraction of the triplet 3 (TX-FLCOOH)*. No polymerization was observed when TX-FLCOONa was used as photoinitiator in the absence of a co-initiator. However, TX-FLCOONa acts as an efficient initiator in the visible range in the presence of H donors in water.

Photoinitiated metal-free controlled living radical polymerization of (meth)­acrylates, and vinyl monomers was investigated using the polynuclear aromatic compounds pyrene and anthracene. Fluorescence spectral analyses along with nuclear magnetic resonance studies were performed to determine the rate constants of initiator radical formation and to investigate the mechanisms of polymerization. The obtained polymers were analyzed by spectral and chromatographic methods. Results show that the excited state anthracene undergoes a faster electron transfer reaction with the alkyl halide initiator than the excited state of pyrene. Pyrene excimers, which are formed at higher concentrations, also react with alkyl halides to form initiator radicals. Although pyrene monomers and excimers are acting slower, polymers with higher control over the chain end functionalities and molecular weight characteristics are obtained in comparison to anthracene as sensitizer.

The application of photochemistry in polymer synthesis is of interest due to the unique possibilities offered compared to thermochemistry, including topological and temporal control, rapid polymerization, sustainable low‐energy processes, and environmentally benign features leading to established and emerging applications in adhesives, coatings, adaptive manufacturing, etc. In particular, the utilization of photochemistry in controlled/living polymerizations often offers the capability for precise control over the macromolecular structure and chain length in addition to the associated advantages of photochemistry. Herein, the latest developments in photocontrolled living radical and cationic polymerizations and their combinations for application in polymer syntheses are discussed. This Review summarizes and highlights recent studies in the emerging area of photoinduced controlled/living polymerizations. A discussion of mechanistic details highlights differences as well as parallels between different systems for different polymerization methods and monomer applicability.