Ronald P. D’Amelia^1,, Evan H. Kreth¹

Differential scanning calorimetry (DSC) is a thermoanalytical technique in which the electrical power needed to maintain an equivalent temperature between the sample and reference is recorded as a function of temperature. One particular use of DSC is to measure glass transition temperatures (Tg), or the temperature at which an amorphous polymer changes from a hard, glassy state to a soft, rubbery one. As the molecular weight (MW) of an amorphous polymer increases, its glass transition temperature also increases, but ultimately levels off at a maximum value labeled Tg_∞. Poly (2-vinyl pyridine) (P2VP) is a versatile polymer, often copolymerized with styrene and butadiene to provide adhesion between the fabric and rubber of vehicle tires. DSC was used to evaluate the Tg of several samples of P2VP spanning a wide range of MW. These Tg were plotted as a function of reciprocal number average molecular weight (Mn), producing a Flory-Fox equation of Tg = 112°C – 1.5e+5°C·g·mol^-1Mn^-1 (r² > 0.99). The Tg resulting from prepared binary mixtures of different molecular weight P2VP were also studied in this experiment. Predicted values of the resulting glass transition temperatures were calculated utilizing the Fox equation: Tg^-1 = w₁Tg₁^-1 + w₂Tg₂^-1 where w represents the weight percent of each molecular weight P2VP component. Resulting Tg were fitted with exponential trendlines (r² > 0.97) and aligned closely to the Tg predicted by the Fox equation.

Poly(2-vinylpyridine) (P2VP), Flory-Fox equation, Fox equation, glass transition temperature (Tg), differential scanning calorimetry (DSC), polydispersity index (PDI)