Orientation behavior and in-situ photopolymerization of two mesogenic acrylates

ABSTRACT IR spectroscopy was used to analyze the orientation behavior and in-situ photopolymerization of two mesogenicacrylates in the chiral smectic I (S, ) phase and in the SA phase, respectively. The orientation parameter, 5, wasdetermined using unpolarized radiation and by comparing the spectra of the mesophase with those of the isotropicphase. The type of alignment was deduced from the observation that the absorption is higher in the mesophase thanin the isotropic phase for vibrations perpendicular to the mesogenic core. The change in the relative intensity of thebands with opposite direction of transition moments showed that the long axis of the mesogenic cores is tilted fromthe direction of the incident beam. The S value was found to be 0.65 over a wide temperature range of the 5; phase,while that in the SA phase gradually growths as the temperature falls achieving 0.72 before crystallization. In the absence of a photoinitiator, UV irradiation of the monomeric films resulted in fast and efficient polymerization. Theconversion of the monomers was shown to be practically complete upon UV irradiation. The S value of the polymeric