Synthesis and properties of ultraviolet-curable resins via a thio-ene (thiol and allyl) addition reaction

Benzophenone diallyl ester (1) and benzophenone tetraallyl ester (II) based on 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) with allyl alcohol (AAL) were synthesized. Glycidyl methacrylate (GMA) was added to I and formed diallyl diglycidyl methacrylate (III). These BTDA-based allyl-containing compounds (II and III) reacted with 1,4-butanedithiol and 4,4'-thiol-bisbenzenethiol to produce ultraviolet (UV)-curable resins via a thioene addition reaction. The ester (III) was cured easily when exposed to UV or sunlight radiation without any photoinitiator and only required a lower thermal curing temperature. The diallyl ester (I) and tetraallyl ester (II) required the addition of benzophenone to increase the photosensitivity, which reduced the exposition time. These resins used AAL as a monomer to successfully reduce the oxygen effect of the photocuring. The resin BTDA-2Allyl-2GMA had a glass-transition temperature of 166degreesC and a hardness of 6H. The resultant UV-curable coatings had excellent hardness, chemical resistance, adhesion, and tensile properties. (C) 2002 Wiley Periodicals, Inc.