On the Photodegradation of Some 2H-Chromene Derivatives in Fluid Solution or in Polyurethane Matrix

The time profile of the optical density was monitored during the photodegradation of three derivatives of 2,2-diphenyl-2H-naphtho[1,2-b]pyran (1), namely 2,2-bis(4-methoxyphenyl)-5,6-dimethyl-2H-naphtho[1,2-b]pyran (2), 2,2-diphenyl-5-[(ethoxycarbonyl)methoxycarbonyl]-8-methyl-2H-naphtho[1,2-b]pyran (3), and 3,3-bis(4-methoxyphenyl)-6,11-dimethyl-13-hydroxy-13-isopropyl-3H-indeno[2,1-f]naphtho[1,2-b]pyran (4) either in toluene solution or in a polyurethane matrix. The photoproducts were identified using HPLC, GC/MS, and direct insertion MS techniques. High molecular weight oxygenated derivatives and new photoproducts deriving from a secondary oxidative pathway were characterized along with expected degradation derivatives. Some of the photoproducts considered responsible for the yellowing of the examined materials were identified. The effect exerted by two additives generally considered to have an inhibiting action toward radical processes was also evaluated.