Action of Light on Sodium-Butadiene Rubber

Abstract

Abstract An apparatus was devised and experimental methods of investigating the action of light on polymers in a high vacuum (10™6 mm. of mercury) were developed. The limits of accuracy of the methods for measuring gas formation and decrease of unsaturation are 1–2 per cent. The effect of ultraviolet radiation on sodium-butadiene rubber in a high vacuum is the formation of gaseous byproducts. The latter appear as two fractions: one which condenses at 180° C, and one which does not condense under the same conditions. The noncondensing part comprised 84 per cent of the total, and consisted of 64 per cent hydrogen and 32 per cent methane; this indicates rupture of the —C—C— and —C—H bonds. The action of light on rubber is accompanied by a loss of unsaturation. The change of unsaturation is primarily in the main chains and only to a small degree in the side chains (we know that the reverse is true with respect to the effect of heat). Measurements were made of the light energy absorbed by rubber, and the quantum yield of gaseous products was calculated. The small quantum yield (2×10−3) indicates the incatenate nature of the process. The decrease of solubility of an irradiated polymer is a consequence of a reaction between free radicals forming after rupture of the —C—H bond, and also after rupture of the carbon chain.