Morphology and orientational order of nematic liquid crystal droplets confined in a polymer matrix.
The orientational order of nematic liquid crystal (LC) droplets confined in a polymer matrix is investigated by 13C-NMR. Different morphologies exhibiting various cavity sizes were obtained by changing the LC fraction. The phase diagram has been established by polarized optical microscopy exhibiting a typical upper critical solution temperature shape. The nematic order increases with decreasing droplet size which may result from increased polymer/LC surface contacts in smaller cavities. The nematic fraction of 4-n-pentyl-4'-cyanobiphenyl (5CB) contained in the droplets was calculated by integrating the NMR peaks, then fitted using a simple theoretical model and compared with differential scanning calorimetry results. NMR investigations in the aliphatic region of the spectra have shown that the 2-ethyl hexyl fragment of the polymer chain is partially ordered at the polymer/LC interface due to interdigitation with 5CB molecules. Above the nematic-isotropic transition temperature, a weak pretransitional behavior is shown by the polymer.
Roussel
Frédérick
F
Laboratoire de Thermophysique de la Matière Condensée, Equipe de l'UPRESA CNRS 8024, Université du Littoral-Côte d'Opale, MREID, 59140 Dunkerque, France. Frederick.Roussel@purple.univ-littoral.fr
Canlet
Cécile
C
Fung
Bing M
BM