Syntheses and alignment behavior of liquid crystalline polymethacrylates having 2‐ and 4‐styrylpyridine moieties

Abstract

Two kinds of polymethacrylates, 1 and 2, with 2-styrylpyridine and 4styrylpyridine moiety as a photoreactive group, which have a benzoate group as a mesogenic unit, and hexylene group as a flexible spacer in the same side chain, were synthesized to characterize their alignment behaviors. The UV absorption and fluorescence studies on the two polymers revealed that the latter polymer with the 4-stylrylpyridine moiety is more aggregative than the former polymer with the 2-styrylpyridine moiety. The polymer 1 showed a nematic phase structure at 170 8C, while 2 appeared in a partially bilayered smectic A phase structure in the homeotropic direction at 175 8C. The polymer 1 film generated an in-plane alignment by a linearly polarized UV light irradiation and subsequent annealing, and its direction was parallel with respect to the irradiation. On the other hand, the polymer 2 film with the same treatments gave a high out-of-plane order parameter of 0.73 in a wide temperature range of 120-240 8C. The significant differences in the aggregation behavior, the liquid-crystalline structure, and the alignment between the two polymers were discussed by the structural differences between the 2-and 4-styrylpyridine moieties in the two polymers. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5371-5380, 2008

High out-of-plane alignment of liquid crystalline methacrylate copolymer bearing photoreactive 4-styrylpyridine moiety

“…Therefore, this result indicates that the copolymer forms a smectic structure with a partial bilayer spacing. 16 In addition, the POM photograph of the copolymer revealed a characteristic birefringent texture at 165 o C. Figure 4 displays the UV spectra of the copolymer film exposed to UV light with various exposure doses. The absorbances of the film around both 300 and 260 nm decreased with an increase in the exposure dose.…”

“…This value was almost similar to that of a homopolymer from 1. 16 However, the solubility of this copolymer for organic solvents was better than that of the homopolymer. 16 Moreover, the copolymer has less amount of the photoreactive group compared to the homopolymer.…”

“…16 However, the solubility of this copolymer for organic solvents was better than that of the homopolymer. 16 Moreover, the copolymer has less amount of the photoreactive group compared to the homopolymer. In these viewpoints, the former polymer is more convenient for applications than the latter polymer.…”

“…16 Another comonomer with a mesogenic 4-methoxyphenyl benzoate unit, 6-[4-(4-methoxyphenyloxycarbonyl)-phenoxy]hexylmethacrylate (2) was prepared from 4-methoxyphenol, 6-bromo-1-hexanol, 4-hydroxybenzoic acid, and *Corresponding Author. E-mail: wskim@knu.ac.kr methacrylic acid according to the literature.…”

“…The role of 4-styrylpyridine structure for outof-plane alignment of the polymer was discussed in detail. 16 Considering alignment behaviors with these structural factors, other photosensitive LC polymers with high out-of-plane alignment ability could be LC copolymers of 4-styrylpyridine group-containing monomers and mesogenic groupcontaining monomers. The copolymers are more convenient for storage compared to the LC homopolymer with 4-styrylpyridine moiety described above because of less amount of the photosensitive group in the former polymer.…”