Design of new photoactive materials exhibiting nano-organization aiming for smart practical applications remains an actual and highlighted task. The synthesis and comparative study of chiral liquid crystalline polymethacrylates with azobenzene groups having lateral methyl substituents were carried out to contribute to a better understanding of their structure−property relationship. The synthesized polymers possess the same photochromic fragment and differ in the length of the spacer (m) and the terminal chiral group (n, 6 and 10 methylene units). Racemic analogues of the chiral polymethacrylates were also synthesized and studied. The effects of chirality and length of the spacer of the terminal alkyl groups on the mesomorphic behavior and photo-optical properties were established. Depending on the chemical structure of the variable fragments and chirality, the polymers exhibit the nematic, the cholesteric, the orthogonal smectic A, and other smectic phases. The presence of the lateral methyl substituent in the photochrome/mesogen fragment leads to a significant decrease in isotropization temperature compared with the same azobenzene-containing polymers without lateral substitution. The photoorientation processes under illumination with polarized visible light (457 nm) are studied for the amorphousized films of the investigated liquid crystalline polymethacrylates. It was found that an increase in the spacer length leads to an increase in the value of photoinduced dichroism (ΔD = 0.28). The maximal photoinduced dichroism is independent of the length of the terminal chiral group. The maximal dichroism (D = 0.78) under polarized visible light irradiation is found for the polymers with m = 10 and n = 6. Upon annealing the irradiated polymer films at room temperature, a reversible change in the dichroism value was observed. Chirality plays a significant role in the relaxation behavior of the irradiated enantiopure and racemic films of polymers with a long spacer and alkyl tail (10 methylene units).

Stimuli responsive liquid crystalline polymers are a unique class of so‐called “smart” materials demonstrating various types of mesomorphic structures easily controlled by external fields, including light. In the present work we synthesized and studied a comb‐shaped hydrazone‐containing copolyacrylate exhibited cholesteric liquid crystalline properties with the pitch length of the helix being tuned under irradiation with light. In the cholesteric phase selective light reflection in the near IR spectral range (1650 nm) was measured and a large blue shift of the reflection peak from 1650 nm to 500 nm was found under blue light (428 or 457 nm) irradiation. This shift is related to the Z‐E isomerization of photochromic hydrazone‐containing groups and it is photochemically reversible. The improved and faster photo‐optical response was found after copolymer doping with 10 wt % of low‐molar‐mass liquid crystal. It is noteworthy that both, the E and Z isomers of hydrazone photochromic group are thermally stable that enable to achieve a pure photoinduced switch without any dark relaxation at any temperatures. The large photoinduced shift of the selective light reflection, together with thermal bistability, makes such systems promising for applications in photonics.

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