Glass transition temperatures in binary polymer blends

Knowledge of the glass transition temperatures ( T g s) as function of composition reflects miscibility (or lack of it) and is decisive for virtually all properties of polymer‐based materials. In this article, we analyze single blend‐average and effective T g s of miscible polymer blends in full concentration ranges. Shortcomings of the extant equations are discussed to support the need for an alternative. Focusing on the deviation from a linear relationship, defined as Δ T g = T g − φ 1 T g,1 − φ 2 T g,2 (where φ i and T g, i are, respectively, the weight fraction and the T g of the i ‐th component), a recently proposed equation for the blend T g as a function of composition is tested extensively. This equation is simple; a quadratic polynomial centered around 2φ 1 − 1 = 0 is defined to represent deviations from linearity, and up to three parameters are used. The number of parameters needed to describe the experimental data, along with their magnitude and sign, provide a measure of the system complexity. For most binary polymer systems tested, the results obtained with the new equation are better than those attained from existing T g equations. The key parameter of the equation a 0 is related to parameters commonly used to represent intersegmental interactions and miscibility in binary polymer blends.