Studies on Aminoanthraquinone Compounds II—Photochemistry of Dyed Polymer Films

Abstract

A study has been made of the action of near ultraviolet radiation and visible light on transparent polymer films of cellulose acetate, nylon, and N‐methoxymethylnylon dyed with six aminoanthraquinones (1‐ and 2‐mono‐, 1:4‐ and 1:5‐di‐, 1:4:5‐tri‐, and 1:4:5:8‐tetra‐aminoanthraquinone). The reaction was followed spectrophotometrically in a closed system of dry nitrogen or oxygen. The general feature of the exposures in oxygen is a decrease in optical density throughout the spectrum. This is particularly a feature with the 1‐ and 2‐amino compounds. With the derivatives substituted in the 1 and 4 positions there is a reduction in the intensity of the twin peaks in the visible region, the rate of decrease being greater for the peak at longer wavelength, and in some cases a general absorption band replaces the twin peak system. The rate of fading of 2‐aminoanthraquinone on nylon and cellulose acetate film is as great in nitrogen as in oxygen, although with 1:5‐diaminoanthraquinone the rate is greater in oxygen. The light fastness of the aminoanthraquinones is greatest on cellulose acetate film, intermediate on nylon, and least on N‐methoxymethylnylon. Among the six aminoanthraquinones the light fastness on a particular substrate is least with 2‐amino‐ and 1:5‐diamino‐anthraquinone, and greatest with the 1, 1:4, 1:4:5, and 1:4:5:8 compounds. On exposure in nitrogen, but not in oxygen, of 1‐amino‐ and 1:5‐diamino‐anthraquinone on N‐methoxymethylnylon, a new peak around 400 mμ. is formed. Under the same conditions 2‐aminoanthraquinone behaves differently.