Photoinduced Alignment of Polymer Liquid Crystals Containing Azobenzene Moieties in the Side Chain. 3. Effect of Structure of Photochromic Moieties on Alignment Behavior

Abstract

Photoinduced alignment behavior in a series of polymer liquid crystals containing different azobenzene moieties in the side chain was investigated. With increase of the strength of donor and acceptor at 4 and 4‘ positions of the azobenzene groups, the possibility of an alignment change in the polymer liquid crystals having the same methacrylic backbone decreased due to the slightly increased enthalpic stability of the mesophase and the significantly decreased concentration of cis-azobenzene, although the cis−trans isomerization rate increased. However, a high alignment efficiency was observed in polymer liquid crystal ACB-ABA6, which contained strong donor−acceptor pairs in the azobenzene moiety and exhibited low stability of mesophase, since both the rate of cis−trans isomerization and the mobility of mesogens are favorable for alignment change. Three different relaxation processes were observed in the aligned polymer liquid crystals.

The enhancement effect of hydrogen bond on the third-order nonlinear optical properties

“…With the number of C 2 H 4 OH group increasing, the absorption maximum further shifts toward longer wavelengths: 458, 385, 310 nm for 3b to 464, 387, 313 for 3c. This may be explained by J-type aggregation and regular arrangement of azobenzene molecules due to strong interactions of hydroxyl group in the substituents through hydrogen bond formation [23]. The similar phenomena were observed in the system of Wu et al [23].…”

Control of Thermally Enhanced Photoinduced Reorientation of Polymethacrylate Films with 4-Methoxyazobenzene Side Groups by Irradiating with 365 and 633 nm Light and Annealing

“…[17][18][19] The influence of the irradiating temperature on the photoinduced reorientation in 4-substituted azobenzene containing polymers was also investigated. 19,[24][25][26] These findings imply that the annealing conditions are important for the reorientation behavior of azobenzene-containing polymers. However, based on the axis-selective E-to-Z photoisomerization, the azobenzene groups do not induce an in-plane reorientation parallel to E.…”

Thermotropic side chain polyacrylates with azobenzene mesogenic groups: Synthesis and thermal behaviour

“…[1][2][3][4][5] While the rigidity and the planarity of an azobenzene group provide anisotropy of shape required for LC properties, it has structural features that can be modified to incorporate such property profiles for photo responsive behaviour. [6,7] Recently, we have shown that a main chain polymer containing azobenzene mesogens to which a long alkyl substituent is laterally attached is potentially a NLO material.…”