Evaluation of the Flory-Fox Equation for the Relationship of Glass Transition Temperature (Tg) vs Molar Mass of Poly (tert-Butyl Methacrylate (PtBMA) Using Differential Scanning Calorimetry (DSC)

Glass transition temperature (Tg), termed the “softening point of amorphous materials” is the temperature at which an amorphous material changes from a hard, glassy state to a soft, rubbery one. As the number-average molecular weight (Mn) of the amorphous material increases, its glass transition temperature also increases, but ultimately levels off asymptotically at a maximum value labeled Tg∞. Differential scanning calorimetry (DSC) was utilized to evaluate Tg for eight samples of poly t-butyl methacrylate (PtBMA) whose Mn values ranged from approximately 1K to 500K. These values were then plotted against reciprocal Mn, producing a Flory-Fox equation of Tg = 114.7°C – .55 x 10 5 C.g.mol-1/Mn, with a correlation coefficient of 0.98. These experiments demonstrate the quantitative applications of DSC in evaluating the Flory-Fox equation for Poly (t-Butyl Methacrylate (PtBMA) as well as its suitability within the undergraduate chemistry laboratory.