Ronald P. D’Amelia^1,, Brandon Khanyan¹

Differential Scanning Calorimetry (DSC) is a technique which measures heat flow to study phase transitions, thermodynamic properties, and oxidation reactions. One particular use of the technique is to observe glass transition temperatures of polymers by measuring the energy changes upon heating. The experiment entails the measurement of glass transition temperatures and enthalpies of transition for monodispersed polystyrene (PS) samples, as well as the analysis of binary mixtures ranging from 0% to 100% in 20% intervals of monodispersed polystyrene of various molecular weights. The results corroborate the molecular weight dependent of glass transition temperature curve for monodispersed polystyrene as predicted by the Flory-Fox equation, T_g = T_g,∞ - K / M_n. The second goal of the experiment is to determine the weight percent proportion in each of the mixtures studied. The experimental results for the polystyrene mixtures show a strong, linear correlation between the theoretical and experimental glass transition temperatures found using DSC. The experiment is designed to demonstrate the applicability of the Flory-Fox equation and to increase awareness of the applications of DSC that could be integrated into undergraduate analytical and instrumental polymer chemistry laboratory course curriculums.

Differential Scanning Calorimetry, polystyrene, binary polystyrene mixtures, Flory-Fox equation, Glass transition temperature T_g , undergraduate laboratory experiment