Patterned retarders prepared by photoisomerization and photopolymerization of liquid crystalline films

Abstract

Isomerizable diacrylates derived from cinnamic acid are designed, synthesized and mixed with liquid crystalline diacrylates with the aim of making films with alternating birefringent and isotropic domains by applying the E-Z isomerization process at room temperature. The effects of the structure of the isomerizable-mesogenic group on the isotropization efficacy, the efficiency of the E-Z isomerization reaction, and film formation are discussed. Compounds derived from cyclohexyl cinnamate are proved to be good candidates that meet a whole set of parameters related to processing and application. These compounds exhibit a low nematic-toisotropic transition temperature. In addition, they show no yellowing upon irradiation, unlike similar compounds derived from phenyl cinnamate. To elucidate the origin of isotropization of the film by irradiation, the pure Z-isomer is prepared by photolysis of the E-isomer and subsequent chromatographic separation of both isomers. Analysis of reference samples containing the pure isomers reveals that the decrease in transition temperature can be attributed exclusively to the E-Z photoisomerization process. Finally, thin films with alternating birefringent and isotropic parts of 1006100 mm 2 are obtained by using a combination of photoisomerization in air and photopolymerization in a nitrogen atmosphere, which is referred to as photo-patterning.

Fluorophobic Effect Promoting Lamellar Self‐Assembly of Donor Acceptor Dyes

“…In addition, due to the fact that E/Z mixtures of the merocyanines were employed in the current study, we surmised that an increasing amount of bent Z isomer should decrease the mesophase stability in a similar fashion as was reported previously by Meier, Lakehal, Sworakowski, Bobrovsky, and Saïdi‐Besbes albeit to a smaller extent because the respective double bond is not located in the centre of the merocyanine in contrast to the previously reported stilbenes, azobenzenes and the like. The results in Figure suggest that the amount of E ‐isomer indeed contributes to the mesophase range and stability.…”

Field in Focus with a Maximum Longitudinal Electric Component

“…The optimum pupil field is found to be radially polarized; however, the amplitude is not of doughnut type but increases monotonically with distance to the optical axis in a way that depends on the numerical aperture. This pupil field is easy to realize using, for example, liquid crystal-based devices [13][14][15][16]. The full-width-athalf-maximum of the squared amplitude of the maximum longitudinal component is, depending on the numerical aperture, 15% to 30% less than that of the classical Airy spot.…”

Focused fields of given power with maximum electric field components

“…The focused wavefront can be tailored by setting a proper amplitude, phase and polarization distributions in the pupil of the focusing lens. Nowadays it is possible to realize almost any complex transmission function in the pupil plane, using for example liquid crystal-based devices [10], [11], [12], [13], [14].…”