Application of dye techniques in the study of chain-transfer properties of thiols

Abstract

Dye techniques (dye partition technique in particular) have been found to be simple and sensitive methods for studying the chain transfer properties of substituted thiols containing ionic or ionogenic groups (amenable to dye test). These are: 2-Mercapto ethanol, 2-mercapto ethylamine hydrochloride, and thioglycolic acid. C_tr values obtained by this method are found to agree fairly well with those obtained from conventional DP methods. Arrhenius parameters and some thermodynamic functions have been evaluated from experimentally determined C_tr values. Existence of a negative temperature coefficient is found for the transfer process of the thiols with PMMA radicals. Transfer potency of the thiols is found to be dependent on their structure. Thus C_s value for 2-mercapto ethylaminehydrochloride with MMA is found to be least in the present series which can be accounted for the presence of a strong electron accepting group in the thiol which vehemently opposes the electron transfer from the thiol to the electron accpeting PMMA radical in the transition state.