Molecular simulations of the miscibility in binary mixtures of PVDF and POSS compounds

Abstract

The miscibility behavior of binary mixtures of poly(vinylidene difluoride) (PVDF) and six different kinds of polyhedral oligomeric silsesquioxanes (POSS) compounds ((ethylic)8Si8O12 (E-POSS), (phenyl)8Si8O12 (P-POSS), (3, 3, 3-trifluoropropyl)8Si8O12(FP-POSS), (1H, 1H, 2H, 2H-nonafluorohexyl)8Si8O12 (FH-POSS), (1H, 1H, 2H, 2H-tridecafluorooctyl)8Si8O12 (FO-POSS) and (1H, 1H, 2H, 2H-heptadecafluorodecyl)8Si8O12 (FD-POSS)) was studied using molecular simulations and the extended Flory–Huggins model. First, the pairwise binding energies Eij and coordination numbers Zij were computed by means of a Monte Carlo approach. Then the mixing energies Emix, the Flory–Huggins interaction parameters χ and the free energies ΔGmix in the temperature range 100–600 K and phase diagrams of the six different mixtures were obtained. All these results indicate that PVDF/FP-POSS, PVDF/FH-POSS, PVDF/FO-POSS and PVDF/FD-POSS are fully miscible at any temperature. PVDF/E-POSS and PVDF/P-POSS are immiscible except at very high temperatures. The lowest energy frames and the frame energies show that the miscibility of PVDF and the four kinds of fluorinated POSS compounds is derived from the polar C–F bonds and the electrostatic interactions in their molecules.