Thermal Characterization of Polymer-Dispersed Liquid Crystals by Differential Scanning Calorimetry

Graham M. Russell, Brian J.A. Paterson, Corrie T. Imrie*, S. Karl Heeks

*Corresponding author for this work

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

The thermal behavior of polymer-dispersed liquid crystals prepared by polymerizationinduced phase separation has been characterized using differential scanning calorimetry and polarized light microscopy. The thermally cured system studied, PolyBed 812/4-n-pentyl- 4'-cyanobiphenyl (5CB), exhibited molecular mixing up to at least 30 wt % 5CB. The liquidcrystal solubility limit, A, in the polymer matrix was calculated to be 41.8. Above 60 wt % 5CB the mixtures exhibited macroscopic as well as microscopic phase separation, and this was detected as a splitting of the nematic-isotropic peak in the DSC thermograms. The nematic-isotropic transition temperature and associated enthalpy suggested that the phaseseparated liquid crystal contained very small amounts of either prepolymer or partially cured polymer. A UV-cured system was investigated also, namely, Norland Optical Adhesive 65 (NOA65)/5CB. A very similar value of A, 42.1, was calculated for this system. For the NOA65/5CB mixtures macroscopic phase separation was not observed. The nematic droplets exhibited clearing temperatures equal to that of pure 5CB within experimental error, implying that essentially pure 5CB separates from the polymer matrix.

Original languageEnglish
Pages (from-to)2185-2189
Number of pages5
JournalChemistry of Materials
Volume7
Issue number11
DOIs
Publication statusPublished - 1 Jan 1995

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