Photolysis of the azide group of linear polyester containing 3-azido-o-phthalic groups

Abstract

This paper presents the results of a study on the photolysis of the azide group in polyesters of 3-azido-ortho-phthalic acid and linear diols. It was stated that the apparent quantum yield of the azide group photolysis depends on the number of carbons separating the azide group and on the diol type, being different for diols with even and odd numbers of carbons. The formulated kinetic equation takes into account the effect of the initial concentration of the azide group on the rate of photolysis. Investigation of all the polyesters with a constant initial concentration of azide groups showed that the number of carbons in a diol does not affect the real quantum yield. However, it is affected by whether that number is odd or even. A value for the activation energy of photolysis was also determined. It amounts to E_a = 1·6 kcal mol⁻¹ for polyesters with an odd number of carbons in the diol, and E_a = 0·34 kcal mol⁻¹ for polyesters with an even number of carbons in the diol. It can be concluded from the research that the way of introducing the light-sensitive group into the polymer chain is decisive for the primary processes in the polymer under irradiation. The real quantum yield for the light-sensitive group attached to the main chain amounts to φ = 0·61. For the light-sensitive group introduced into the polymer chain this value is smaller; for polymers with an even number of carbons in the diol φ = 0·42−0·47 and for polymers with an odd number of carbons in the diol φ = 0·51−0·54.