KEY WORDSPoly-functional Amines/ Photo-generation/ Thermal Curing Reaction / Epoxy Resin / Polyurethane Oligomer / Photo-generation of corresponding free amines by decomposition of 2-nitrobenzyl carbamates, 1 formanilides 2 as well as photoFries type rearrangement 3 of acetanilide has been reported. Recently, Kutal and Willson reported 4 the photo-generation of ammonia by UV irradiation of a cobalt-amine complex and thermo-crosslinking reaction of poly(glycidyl methacrylate-co-ethyl methacrylate) using the generated ammonia. This photoinduced thermo-crosslinking reaction pointed out a new photoresist technology. Tsunooka et al. also reported 5 photo-generation of free amines from O-acyloxyamines in poly(glycidyl methacrylate) film and thermo-crosslinking reaction of the polymer film. Cameron and Frechet reported 6 ' 7 photo-generation of free hexane-It is also well known that poly-functional amines are very important reagents for thermo-crosslinking reactions of epoxy resins and polyurethane oligomers with terminal isocyanate groups in adhesives, paints, coatings, composites, etc. However, the storage stability of mixtures of epoxy resins and polyurethane oligomers with poly-functional amines, especially with aliphatic diamines, is not good enough at room temperature, since poly-functional amines have high chemical reactivity.Therefore, the photo-generation of polyfunctional free amines from the blocked amine groups by UV irradiation and applications for curative formulations of epoxy resins and polyurethane oligomers are very important and a new advanced concept in polymer chemistry. However, there has been no report on thermo-crosslinking reaction of the epoxy resins or the polyurethane oligomers with photo-generated poly-functional amines.This communication reports on the photogeneration of free diamines and applications for thermal curing reaction of epoxy resins and polyurethane oligomers with terminal isocyanate groups.

Photochemical reactions of various blocked polyfunctional amines such as bis(4‐formylaminophenyl)methane (FAPM), bis(4‐acetylaminophenyl)methane (AAPM), bis(4‐benzoylaminophenyl)methane (BAPM), 2,4‐diformylaminotoluene (DFAT), m‐xylene diformamide, and bis[[(2‐nitrobenzyl)oxy]carbonyl]hexane‐1.6‐diamine were carried out to give the corresponding free amines in THF solution, in epoxy resin, or in polyurethane oligomer with terminal isocyanate groups. Photolysis of FAPM and DFAT to produce the corresponding polyfunctional amines such as 4,4'‐methylenedianiline and 2,4‐diaminotoluene proceeded with 80 and 75% conversions, respectively, in THF solution under UV irradiation at 5 h. AAPM and BAPM also produced the corresponding photo‐Fries rearrangement products with 32 and 38% conversions, respectively, under the same irradiation conditions. The photolysis of those compounds also occurred with similar conversions in the epoxy resin and in the polyurethane oligomer under UV irradiation; and the thermal curing reactions of the epoxy resin and the polyurethane oligomer with photogenerated polyfunctional amines proceeded smoothly after heating at 140°C for 2 hrs. © 1993 John Wiley & Sons, Inc.

SynopsisSome dimethacrylate oligomers were synthesized by new addition reactions of 2,2-(4-hydroxy-pheny1)propane diglycidyl ether (BPGE) or glycidyl methacrylate (GMA) with phenyl methacrylates such as phenyl methacrylate (PMA), 4-nitrophenyl methacrylate (NPMA), 2,4-dichlorophenyl methacrylate (DCPMA), 4-methoxyphenyl methacrylate (MPMA), and (4-cinnamoy-1oxy)phenyl methacrylate (CIPMA) using tetrabutylammonium bromide as a catalyst a t 120°C. The other new dimethacrylate or diacrylate oligomers were also prepared by the addition reactions of GMA or glycidyl acrylate with active esters such as di(S-pheny1)thioisophthalate (PTIP), di(4-nitropheny1)isophthalate (NPIP), di(4-nitropheny1)adipate (NPAD), and di(4-nitropheny1)sebacate (NPSB) under similar reaction conditions. Furthermore, the rates of photochemical reaction of the obtained dimethacrylate oligomers were measured with 3 mol % of various photosensitizers such as benzoin Iso-propyl ether (BIPE), 2-ethylanthraquinone (EAQ), and benzophenone (BP). The rate of photochemical reaction of BPGE-DCPMA oligomer was higher than those of BPGE-PMA, BPGE-NPMA, and BPGE-MPMA oligomers using BIPE as a photosensitizer. However, the photochemical reactivity of the unsensitized BPGE-CIPMA was almost the same as that of the sensitized BPGE-DCPMA. On the other hand, when EAQ was used as a photosensitizer, GMA-PTIP oligomer showed much higher reactivity than GMA-NPAD, GMA-NPSB, and GMA-NPIP oligomers. Also it was shown that the activity of EAQ as a sensitizer was higher than BIPE and BP in the photochemical reaction of BPGE-DCPMA oligomer.

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