Axis-selective photoreaction, photoinduced orientation, and formation of surface relief (SR) gratings of liquid crystalline polymethacrylates comprised of N-benzylideneaniline (NBA) derivative side groups are explored. Irradiating with linearly polarized (LP) 313 nm light generates molecular reorientation of the NBA side groups based on the axis-selective trans−cis−trans photoisomerization and photocleavage of the NBA groups. The inplane order parameter (S) and birefringence (Δn) are ∼0.53 and ∼0.16, respectively. Furthermore, thermally stimulated amplification of the photoinduced optical anisotropy occurs upon exposing films to LP 313 nm light and subsequently annealing in the liquid crystalline temperature range of the material. The amplified S and Δn values are ∼0.71 and ∼0.21, respectively. Finally, polarization holography using 325 nm He−Cd laser beams with various interferometric polarization conditions demonstrates the formation of SR gratings with a molecularly oriented structure based on the periodic photoinduced reorientation and molecular motion.
The
influence of the annealing conditions on the thermally stimulated
photoinduced molecular reorientation of a photoinactive liquid crystalline
polymethacrylate with phenyl aldehyde and benzoic acid side groups
(P1) doped with 4-methoxyaniline, which forms photoalignable
4-methoxy-N-benzylideneaniline (MNBA) side groups in situ, was investigated. Light exposure and subsequent
thermal stimulation under a N2 atmosphere realized sufficient
cooperative molecular reorientation (D > 0.7),
but
the simultaneous thermal hydrolysis of the MNBA groups under humid
air lowered the molecular reorientation performance. By contrast,
subsequent thermal hydrolysis of MNBA after molecular reorientation
introduced different aromatic amines into the reoriented P1 film, which regulated the birefringence and photofunctionality of
the oriented film.
The photoinduced reorientation and surface relief (SR) formation behaviors of a novel photosensitive polymer, which was transparent in visible region, were investigated using linearly polarized-313-nm light and holographic exposure with a 325-nm He-Cd laser. The polymer was comprised of photosensitive 4-methoxy-N-benzylideneaniline side groups, and exhibited a sufficient photoinduced molecular reorientation with a birefringence of 0.11. Holographic exposure generated a SR structure, which had a periodical molecular reorientation that depended on the polarization of the interference beams. The generated SR height was ∼212 nm, and the inscription of a double holographic exposure yielded a two-dimensional SR structure
In this letter, we describe the fabrication of a durable photoalignment layer for liquid crystals (LC) with high azimuthal anchoring and controllability of the tilt angle. A film is irradiated using linearly polarized ultraviolet (LPUV) light followed by annealing which induces the molecular orientation of the photoalignment layer. The nematic LC was aligned parallel to the electric vector of the LPUV light, and the alignment layer showed high thermal stability of the orientational characteristics up to 250 °C.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.