Acrylate benzoin ether photoinitiated

As is shown in Table 5, the (dark) package stability of acrylate and polyester formulations proved to be poor for this class of photoinitiators compared to those developed subsequently. It has been suggested that the instability of benzoin ethers as a class is due to the presence of the readily abstractable benzylic H-atom (2). 

The nematic LC is the original eutectic mixture of 35% (weight %) 4 (m-octyl oxy)-4-cyanobiphenyl (80CB) and 65% 4/-(n-pentyl)-4-cyanobiphenyl (5CB). The sample is doped with perylene and 2% (mol %) of NIAC, which is acrylate monomer containing the easily reduced l,4 5,8-naphthalenediimide moiety (see Scheme 3). Finally, 0.5% (mol %) of benzoin methyl ether (BME) is added to photoinitiate polymerization of the NIAC. 

The efficiencies of benzoin derivatives in promoting the light induced hardening of styrene-containing unsaturated polyester resins have been found to vary considerably (7), benzoin alkyl ethers and a-alkylated benzoins being more reactive than benzoin itself. However, as photoinitiators for the polymerization of bulk methyl methacrylate, benzoin and benzoin methyl ether exhibit comparable efficiencies (20), and this is also indicated for polymerisation of methyl acrylate in tert-butanol (21). The relative photoinitiating efficiencies of benzoin derivatives may be influenced by several factors, some of which will depend on the nature of the monomer system and the environment in which the polymerizations are carried out. 

The reaction of glycidyl acrylate with a-(2-carboxyethyl)benzoin methyl ether has allowed one to obtain [101] the corresponding acrylic monomer which, upon copolymerization with different amounts of MMA, butyl methacrylate and 2-(V, V-dimethylamino)ethyl methacrylate, gives rise to polymeric photoinitiators, containing side-chain benzoin methylether moieties, for photocurable coatings ... 

The polymer-bound photoinitiators have been used to prepare photocurable formulations with epoxyacrylates, urethaneacrylates, trimethylolpropane triacrylate (TMPTA) and HDDA [108]. The above formulations have been UV irradiated on film matrix and the extent of photocuring evaluated in terms of degree of residual acrylic unsaturation at a fixed reaction time. As reported in Table 20, the polymer-bound BAE systems display an appreciably higher photoinitiation activity as compared with that of the low-molecular-weight analogue benzoin isobutyl ether (BIBE) ... 

In order to investigate in more detail the relationships between structure and photoinitiation activity in the polymeric systems based on benzoin methyl ether moieties, poly(MBA) and copolymers of MBA with menthyl acrylate [poly(MBA-co-MtA)s] have also been checked as photoinitiators and compared with the homopolymer of ot-vinyloxymethylbenzoin methyl ether and its copolymers with menthyl vinyl ether [poly(MBVE) and poly(MBVE-co-MtVE)s, respectively] [61,84]. 

Further investigations on polymeric systems containing side-chain benzoin methyl ether and benzoin moieties confirm the enhanced reactivity of the polymeric photoinitiators [111,112]. Indeed, copolymers of MBA with methyl acrylate and methyl methacrylate [poly(MBA-co-MA) and poly(MBA-co-MMA), respectively] and the corresponding copolymers based on a-methylolbenzoin acry-... 

The second type of composition is exemplified by a wide variety of acrylate- or methacrylate-ester derivatives of conventional ink vehicles combined with a photoinitiator 1. The reaction product of tung oil fatty acids, glycidyl methacrylate, -benzoquinone, and 2-methyl-imidazole mixed with tung oil and treated with tolylene diisocyanate, combined with benzoin methyl ether (26) 2. Glycerol-linseed oil-isophthalic acid alkyd reacted with isocyanate-containing prepolymer (formed by reaction of tolylene diisocyanate, -henzoquinone, 2-hydroxypropyl acrylate in ethyl acetate solution) using dibutyltin diacetate catalyst, combined with tung oil, synthetic varnish, and benzoin methyl ether (27) 3. Epoxidized... 

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