On the Glass Transition Phenomenon of Isopentane

Abstract
Heat capacity measurement of isopentane was carried out for crystalline, liquid, glassy, and supercooled liquid states in the temperature region between 13 and 300°K. The glass transition phenomenon of isopentane was found around 65°K with drastic heat capacity change of 68.20 J/mol degK. This glass transition phenomenon is tentatively interpreted in terms of the Adam and Gibbs theory. The value of Tg⁄T2, the ratio of glass transition temperature Tg, and the temperature of disappearance of the configurational entropy of the supercooled liquid T2, for isopentane was found to be 1.30 which is concordant with the value cited by Adam and Gibbs. The residual entropy at absolute zero of the glassy isopentane was shown to be 14.06 J/mol degK. In addition the irreversible production of entropy during the glass transition intervals was found to be 0.08 J/mol degK. It is concluded that the neglect of the irreversible production of entropy leads no significant error in determing the residual entropy.