INVESTIGADORES
SOULE Ezequiel Rodolfo
congresos y reuniones científicas
Título:
Phase Equilibrium and Morphology Study of Direct Isotropic/Smectic-A polymer-Dispersed Liquid Crystals
Autor/es:
EZEQUIEL R. SOULÉ; NASSER M. ABUKHDEIR; ALEJANDRO D. REY
Lugar:
Montreal
Reunión:
Simposio; 6th Interdisciplinary Graduate Student Research Symposium; 2009
Institución organizadora:
McGill University
Resumen:
Experimental and modeling/simulation studies of phase equilibrium and
growth morphologies of novel polymer-dispersed liquid crystal (PDLC)
mixtures of PS (polystyrene) and liquid crystals that exhibit a direct
isotropic/smectic-A (lamellar) mesophase transition were performed for
PS/10CB (decylcyanobiphenyl) and PS/12CB (dodecyl-cyanobiphenyl).
Partial phase diagrams were determined using polarized optical
microscopy (POM) and differential scanning calorimetry (DSC) for
different compositions of both materials, determining both phase
separation (liquid/liquid demixing) and phase ordering (isotropic/
smectic-A transition) temperatures. The Flory-Huggins theory of
isotropic mixing and Maier-Saupe-McMillan theory for smectic-A liquid
crystalline ordering were used to computationally determine phase
diagrams for both systems, showing good agreement with the experimental
results. In addition to thermodynamic observations, growth morphology
relations were found depending on phase transition sequence, quench
rate, and material composition. Three stages of liquid-crystal-rich
domain growth morphology were observed: spherical macroscale domain
growth (stage I), highly anisotropic domain growth (stage II), and
submicrometer spheroid domain growth (stage III). Nanoscale structure
of spheroidal and spherocylindrical morphologies were then determined
via two-dimensional simulation of a high-order Landau-de Gennes model.
Morphologies observed during stage II growth are typical of direct
isotropic/smectic-A phase transitions, such as highly anisotropic
batonnets and filaments. These morphologies, which are found to be
persistent in direct isotropic/smectic-A PDLCs, could provide new
functionality and applications for these functional materials.