Ronald P. D’Amelia^1,, Julia Nastasi¹

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.

Poly tert-Butyl Methacrylate (PtBMA), Poly Methyl Methacrylate (PMMA), Flory-Fox equation, glass transition temperature (Tg), Differential Scanning Calorimetry (DSC)