Phase diagrams and morphology of polymer dispersed liquid crystals based on nematic-liquid-crystal–monofunctional-acrylate mixtures

Abstract

Phase diagrams of unpolymerized and UV-polymerized 2-ethyl hexyl acrylate (EHA) mixtures with the liquid crystal E7 are established using optical microscopy and differential scanning calorimetry. Both diagrams show upper critical solution temperature behavior. From 50 to 90 wt % liquid crystal (LC), the (I+I) phase located between the (N+I) and (I) phases was clearly shown. The nematic phase inside the droplets exhibits a twisted radial structure indicating that homeotropic anchoring occurs at the polymer interface. The experimental phase diagrams were successfully analyzed using a model based on the Flory-Huggins theory of isotropic mixing supplemented with the Maier-Saupe theory of nematic order. The LC solubility limit in the polymer matrix and the fractional amount of LC contained in the droplets were deduced from the calorimetric measurements. For the specific composition EHA/E7 (50:50), the scattering and morphological properties of the films were studied as a function of time elapsed after UV exposure. Drastic changes in the size, shape, spatial distribution, and number density of nematic droplets were observed and analyzed in terms of coalescence/diffusion phenomena.

Preferential solvation of the eutectic mixture of liquid crystals E7 in a polysiloxane

“…Indeed, E7 exhibits a single nematic to isotropic (NI) transition at nearly T NI Z61 8C and no other transitions between C61 and K62 8C, where it shows a glass transition T g . In the majority of cases reported in the literature by us [7,8] and other groups [9,10], these transition temperatures are hardly modified in the presence of a polymer. There are, however, some exceptions which remain to be elucidated involving a phase separation of the constituents of the multicomponent mixture E7 in the presence of certain polymers [1,[11][12][13].…”

Heat transport in polymer-dispersed liquid crystals under electric field

“…of these materials have been extensively investigated. [3][4][5] The aim of this paper is to investigate the thermal properties of PDLC films. These composites offer the opportunity to modify the thermal characteristics of the inclusions without changing physical properties of the system (same num-ber, size and dispersion of inclusions).…”

Maxwell-Wagner-Sillars effects on the thermal-transport properties of polymer-dispersed liquid crystals

“…The undissolved portion of the LC forms droplets. Knowing β and the amount of LC added to the polymer (x), we can calculate the phase-separated LC fraction (φ LC ) using [18][19][20] …”