Synthesis, Dielectric, and Photochemical Study of Liquid Crystalline Main Chain Poly(ester imide)s Containing Cinnamoyl Moieties

Abstract

Photochromic liquid crystalline main chain poly(ester imide)s with cinnamoyl moieties and chiral groups as part of the backbone were characterized concerning their liquid crystalline, molecular dynamical, and photochemical properties. Homo-and copolymers were synthesized by polycondensation of mixtures containing isosorbide, tert-butylhydroquinone, or catechol. The copolyesters were cholesteric, but exclusively the polymers containing the tert-butylhydroquinone moiety form Grandjean textures on annealing. These polymer films show blue iridescent color. UV irradiation causes photo-cross-linking of the polymers via the (2 + 2) photocycloaddition of the cinnamoyl moieties, resulting in insoluble films in which the iridescent supramolecular structure is frozen in without any changes compared to the initial films. Dichroism of about 0.07 is induced upon irradiation with linearly polarized UV light. In contact with liquid crystals, the photoinduced anisotropic interface of the films causes an efficient alignment of liquid crystals.

Liquid crystal photoalignment by soluble photosensitive polyimide with methylene cinnamate side units

“…It has stable alignment ability, good adhesive strength, high moisture resistance, and dimensional stability. 16,17 The LC alignment on a soluble PI film with cinnamate side units was reported to be thermally stable up to 200 o C, as described by Ree et al 13,14 On the other hand, the photosensitivity of these polymers was usually compromised by their rigid main chain. A high exposure dose of 0.5 J/cm 2 was required for the saturated alignment of LCs in these systems.…”

“…The deterioration of aligning performance was observed when the LC cells were annealed at high temperature. 5 Recently, there have been many attempts to improve the thermal stability by using various polymer backbones, such as polyesters, 11 poly(arylene ether), 12 and polyimides, [13][14][15] with crosslinkable chromophores in the structure. Polyimide is the most attractive one owing to its verified properties as an alignment material in the LC industry.…”

Synthesis and Properties of Photo-Cross-Linkable Polymer Liquid Crystal Containing Fluorene Unit

“…Irradiation with linearly polarized ultraviolet (LPUV) light in thin polymer films containing photoreactive moieties induces optical anisotropy and has attracted intensive interest from an practical viewpoint due to the alignment of LCs. A large number of photoreactive polymers have been extensively investigated including azobenzene containing polymers and photo-cross-linkable polymers such as coumarin and cinnamate for the application to LC alignment materials [2][3][4][5][6]. Additionally, various types of copolymer have been also synthesized to obtain higher molecular orientation by the cooperative effect [7][8][9].…”

Effect of photoreactivity of polyimide on the molecular orientation of liquid crystals on photoreactive polymer/polyimide blends

“…LC alignment using ultraviolet (UV) exposure is a promising candidate as a non-rubbing method [1][2][3][4]. Photoalignment layers made from photoreactive polymers with vinylcinnamate and coumarin have shown good LC alignment [3][4][5][6][7], but their thermal stability was poor. In order to enhance the thermal stability of the LC alignment layer, we have previously reported a method using polyimide to enhance the thermal stability of LC alignment layers of polyvinylcinnamate [8,9].…”