Photoinduced Alignment of Polymer Liquid Crystals Containing Azobenzene Moieties in the Side Chain. 5. Effect of the Azo Contents on Alignment Behavior and Enhanced Response

Abstract

A series of side-chain polymer liquid crystals (PLCs) of 6-[4-(4-ethylphenyl)diazenylphenyloxy]hexyl methacrylate and 4′-[6-(methacryloyloxy)hexyloxy]-4-cyanobiphenyl were synthesized and characterized. The effects of contents of the azo units and the wavelength of irradiation light on photoinduced alignment behavior were investigated. On irradiation of linearly polarized light (LPL) at 366 nm directly, alignment change was induced only in the PLC with 6 mol % azo units (P6), while phase transition took place in the other PLCs with higher contents of the azo units. On irradiation of LPL at 436 nm directly, alignment was induced with a fair efficiency in P15 and P35, low efficient alignment was observed in P6 and P100, and no alignment change was induced in P55 and P75, which exhibited a homeotropic state. A high alignment efficiency was achieved in all PLCs by using another method: irradiation with 366 nm unpolarized light at first and then with 436 nm LPL. The alignment change induced by this method was explored at various temperatures. All-optic switching might be realized by irradiation of 336 nm unpolarized light and 436 nm LPL alternatively based on the photochemical phase transition and the photoinduced alignment processes of the PLCs, respectively.

Microscopy and optical manipulation of dendrimer-built vesicles

“…It has been reported that visible light in the range of 436 to 514 nm can induce photoisomerizations in azobenzene. It has to be noted, however, that the amount of cis-azobenzene produced by visible light is much lower than that produced by UV light (e.g., 360 nm) [17]. In our case, irradiation at 420-nm laser light induces trans-to-cis and cis-to-trans photoisomerization cycles, followed by reorientation of azobenzene moieties.…”

Synthesis of New Epoxy Liquid-Crystalline Monomers with Azo Groups in the Central Mesogenic Core. Crosslinking with Amines

“…[3][4][5][6] Such materials have a large induced birefringence, optical anisotropy and high writing-erasing rate.…”

Photoinduced orientation and cooperative motion of three epoxy-based azo polymers

“…The molecular orientation in the polymer films can be quantitatively characterized by the birefringence measurement, polarized UV-Vis spectroscopy, and polarized IR spectroscopy [14,15,24,25]. In past decades, the correlation between the photoinduced orientation and molecular structures has been extensively studied for both liquid crystal azo polymers [12,13,[29][30][31][32][33], and amorphous azo polymers [16][17][18][19][20][21][22][23][24]. Understanding of the structure-property relationships has been used to elucidate the mechanism and develop materials with better performance.…”