ANISOTROPIC NETWORKS WITH TUNABLE OPTICAL AND MECHANICAL-PROPERTIES

Binary mixtures of liquid crystal diacrylates with a stilbene moiety w ere produced. The mixtures were uniaxially oriented and subsequently p hotopolymerized, resulting in anisotropic networks with a uniaxial mol ecular orientation containing stilbene groups in the E (trans) form. I n order to avoid E-Z (trans-cis) isomerization of the stilbene groups during polymerization, the wavelength used to initiate polymerization was chosen to be beyond the absorption band of the stilbene molecules. Transformation of the stilbene groups within the uniaxially oriented networks from the E to the Z form was carried out using UV radiation. As a result of the transformation, the conformation and the polarizabi lity of the stilbene molecules were altered,leading to a decrease in t he birefringence of the anisotropic networks. The magnitude of the dec rease could be varied by the UV exposure time and the fraction of stil bene moieties within the networks. The E-Z isomerization also caused a nisotropic dimensional changes and altered the anisotropic thermal exp ansion behavior of the networks.