Using TS2 Model to Describe the Dynamics of Amorphous Random Copolymers or Miscible Polymer Blends near the Glass Transition

The glass transition in miscible polymer blends or random copolymers has been an important area of research since at least the 1950-s. While Fox, Gordon-Taylor, Kwei, and other equations are able to successfully describe the dependence of Tg on the blend or copolymer composition, they are usually less definitive about the prediction of the fragility and the dependence of the relaxation time on temperature. Here, we extend our recent lattice model of glass-forming systems (two-state, two-(time)scale or TS2¹) to the cases of miscible blends and random copolymers. In particular, we apply the model to the case of PS-PMMA random copolymers, and successfully describe the dielectric spectroscopy results for the α- and β-relaxation times. These results establish mixing rules to enable the generalization of the TS2 approach to heterogeneous systems (phase-separated polymer blends, thin films, and nanocomposites).
¹V. Ginzburg, Soft Matter 16, 810 (2020).