Spinodal Decomposition of Filled Polymer Blends: The Role of the Osmotic Effect of Fillers

Abstract

The reported work addresses the effect of fillers on the thermodynamic stability and miscibility of compressible polymer blends. We calculate the spinodal transition temperature of a filled polymer blend as a function of the interaction energies between the blend species, as well as the blend composition, filler size, and filler volume fraction. The calculation method relies on the developed thermodynamic theory of filled compressible polymer blends. This theory makes it possible to obtain the excess pressure and chemical potential caused by the presence of fillers. As a main result of the reported work, we demonstrate that the presence of neutral (non-adsorbing) fillers can be used to enhance the stability of a polymer blend that shows low critical solution temperature (LCST) behavior. The obtained results highlight the importance of the osmotic effect of fillers on the miscibility of polymer blends. The demonstrated good agreement with the experiment proves that this effect alone can explain the observed filler-induced change in the LCST.

Keywords: filler; polymer blend; spinodal.

Figure 1

The characteristic temperature $T_{12}$ of the cross-species interactions, obtained by the fitting procedure described in the text. The experimental transition temperatures $T_S$ were obtained in [3], and their polynomial interpolation is shown for reference.

Figure 2

Spinodal of the $SAN/PMMA$ blend filled with silica fillers: theory vs. experiment. See explanation in the text. The experimental rheological transition temperatures $T_S$ obtained in [3] and their polynomial interpolation for the unfilled $SAN/PMMA$ blend are shown for reference.