Synthesis and Characterization of a Novel Polymeric System Bearing a Benzophenone Borate Salt as a New Photoinitiator for UV Curing

Abstract

Polymeric photoinitiators bearing benzophenone triphenylbutyl borate salt as the side chain have been synthesized and characterized and their activity measured in the photoinitiated polymerization of a bifunctional monomer, diethylene glycol diacrylate. The results were compared with a low-molecular weight model compound. At lower concentrations of the requisite benzophenone moiety, the highest activity was observed for the model compound, while at higher concentrations the homopolymer was superior. For both cases, the lowest photoinitiation activity was observed with significant induction period for copolymers with methyl methacrylate when compared to the homopolymer. The results are discussed in light of the microenvironment of the initiator fragments in the polymeric systems.

Novel Multifunctional Polymeric Photoinitiators and Photo‐Coinitiators Derived from Hyperbranched Polyglycerol

“…Except for the broad resonance at 4.13 ppm (j), the other broad signals between 4 and 5.5 ppm evidenced successful transformation of the hydroxyl groups of PG into ester groups. Attachment of the DMB moieties to PG was verified by the existence of the broad signals at 2.99 (d), 6.59 (k), and 7.85 ppm (l). The broad single peaks at 3.33 (e) and 4.13 ppm (j) were assigned as the protons of methoxy and methylene groups of MEEA moieties in the resulting polymers.…”

“…[4][5][6][7][8][9][10][11][12] Until only a few PPIs have shown higher photoactivity compared with their corresponding low molecular weight analogs. [6][7][8] Photoinitiators for radical polymerizations can be classified in Norrish type I and II. [1] Norrish type I photoinitiators…”

The influence of a radical structure on the kinetics of photopolymerization

“…There are many examples of two‐component photoinitiating systems working through electron transfer process composed of organic borate salts. Polymethine dyes, 2,4‐diiodo‐6‐butoxy‐3‐fluorone, 5,7‐diiodo‐3‐butoxy‐6‐fluorone, xanthenes, fluorones, benzophenone were used as photosensitizers in such photoinitiating systems . The generation of initiating radicals is a result of decomposition of unstable boranyl radical formed after electron transfer process from borate anion to an excited singlet state of photosensitizer (Scheme ) …”

“…Polymethine dyes, 2,4-diiodo-6-butoxy-3-fluorone, 5,7-diiodo-3-butoxy-6-fluorone, xanthenes, fluorones, benzophenone were used as photosensitizers in such photoinitiating systems. 12,[26][27][28][29][30][31] The generation of initiating radicals is a result of decomposition of unstable boranyl radical formed after electron transfer process from borate anion to an excited singlet state of photosensitizer (Scheme 1). 25,32 Dye/Mercaptans In polymer chemistry organic mercaptans, such as 2mercaptobenzoxazole, 2-mercaptobenzothiazole, or 2mercaptoimidazole are very often used as the hydrogen donors or coinitiators.…”

Photopolymerization: A Review

“…Polymeric photoinitiators bearing benzophenone triphenyl borate salt as the side chain were synthesized, [66] characterized, and their activity measured in the photoinitiated polymerization of a bifunctional monomer, diethylene glycol diacrylate. At lower concentrations of the requisite benzophenone moiety, the highest activity was observed for the model compound, while at higher concentrations the homopolymer was superior.…”