Thermophysical Analysis of Smectic A Domains Confined into a Thermoplastic Polymer Matrix

Abstract

Cloud point measurements and calorimetric properties were considered for binary systems of polystyrene=4cyano-4 0 -n-octylbiphenyl (8CB), and deuterated polystyrene=8CB. The experimental phase diagrams were established using polarizing optical microscopy and differential scanning calorimetry. The experiments were realized in the range of temperatures from 25 to 75 C, in which the 8CB presents a smectic A structure, a nematic and an isotropic phase. The phase behavior of both systems were analyzed using a combination of the Flory-Huggins lattice model for isotropic mixing and the Maier-Saupe-McMillan theories for anisotropic ordering. A good agreement was obtained between theoretical considerations and experimental data.

Phase Diagrams of Polymer-Dispersed Liquid Crystal Systems of Itraconazole/Component Immiscibility Induced by Molecular Anisotropy

“…However, the F–H theory alone cannot be used to describe the phase behavior of a binary composition made of an LC compound with a polymer due to the inherent anisotropy of LC phases. Thus an extended approach to the F–H theory needs to be employed with the total Gibbs free energy of such a system ( f ) represented as the combination of two constituents, the free energy ( f (i) ) of mixing of isotropic liquids, as described by the F–H lattice theory, and the free energy ( f (a) ) due to the anisotropic ordering of molecules. ,− …”

“…The F–H free energy ( f (i) ) of mixing of isotropic liquids can be described by eq , where T is the temperature (in K), R is the gas constant (in J·mol –1 ·K –1 ), ϕ is the volume fraction of the API (ITZ), m is the volume ratio of the polymer to drug volume, and χ is the F–H interaction parameter. The interaction parameter χ characterizes the difference in interaction energies in the mixture; therefore, two situations are possible.…”

“…Thus an extended approach to the F-H theory needs to be employed with the total Gibbs free energy of such a system (f) represented as the combination of two constituents, the free energy (f (i) ) of mixing of isotropic liquids, as described by the F-H lattice theory, and the free energy (f (a) ) due to anisotropic ordering of molecules. 44,[51][52][53] The F-H free energy (f (i) ) of mixing of isotropic liquids can be described by Eqn. 2 51,54 :…”

“…44,[51][52][53] The F-H free energy (f (i) ) of mixing of isotropic liquids can be described by Eqn. 2 51,54 :…”