Functionally integrated liquid crystalline photochromic triple block copolymer with locally light‐ and thermal‐controllable sub‐blocks

Abstract

Photoorientation and reorientation processes induced by illumination of the samples with oppositely directed polarized light and by the thermal treatment were studied for the films of triblock copolymer pAzo 10 -b-pPhM 80 -b-pAzo 10 consisting of a nematic phenyl benzoate central subblock (PhM, DP 5 80) with two terminal smectic azobenzene sub-blocks (Azo, DP 5 10). For amorphized films of triblock copolymer, illumination with polarized light (k 5 546 nm) is shown to be by orientation of only Azo-containing groups, but upon following annealing of the film, PhM groups are adjusted to the orientation of Azo fragments. It was found, that the subsequent illumination of the block copolymer sample with oppositely directed polarized light changes the orientation of azobenzene groups, while the orientation of phenyl benzoate groups is remained unchanged. Thus, the cyclic illumination of the triblock copolymer samples by the linear polarized light and subsequent thermal treatment make it possible to control and fix orientation of azobenzene and phenyl benzoate groups located in different sub-blocks in the desired and independent manner. The comparison of these results with the data on random p(Azo 7 -ran-PhM 30 ) copolymer of the similar composition revealed, that in the random copolymer, both Azo and PhM mesogenic groups are involved in the orientational cooperative process regardless of films process treatment.

Polarization Gratings in Azobenzene‐Based Fully Liquid Crystalline Triblock Copolymer

“…In our previous work, we have synthesized LC photosensitive ABA triblock copolymers comprised of azobenzene (Azo) and non‐photosensitive phenyl benzoate (PhM) units . We have also demonstrated that the irradiation of these materials with linearly polarized light and subsequent annealing offer an efficient tool for the selective control over the orientation of Azo and PhM groups …”

Azobenzene‐containing liquid crystalline poly(methacrylates) with different spacer length as media for holographic grating recording

“…Irradiation of Azo polymer films with linearly polarized light is known to induce the orientation of azobenzene groups perpendicularly to the polarization plane leading to dichroism and birefringence 32–34 . As can be seen from Figure 4A, the saturation value of birefringence photoinduсed in the pM2AzoBu film is almost three times higher in comparison with that of the pM10AzoBu film.…”

Photopatterning of Azobenzene‐Containing Liquid Crystalline Triblock Copolymers: Light‐Induced Anisotropy and Photostabilization

“…[17][18][19][20][21] However, according to our knowledge, there are only a few papers (including our publications) dealing with side-chain photochromic di-and triblock copolymers containing mesogenic groups in each block. [22][23][24][25][26][27] As photochromic fragments in such polymers, azobenzenecontaining groups are most often used. It is well-known, that these groups in azobenzene-containing random comb-shaped copolymers easily undergo the repeated and reversible cyclic processes of trans-cis-trans isomerization under the action of polarized light and this leads to orientation of side groups perpendicular to the electric vector of polarized beam.…”

“…to note that LC (mesogenic groups) and photochromic groups can be linked together in each macromolecule of block copolymers by covalent bonds or by using hydrogen bonding. [24][25][26]33] Due to the advancement of polymer synthetic strategies and techniques including controlled living polymerization with facile post-polymerization -functionalization, a variety of block copolymers with precisely controlled molecular weight and welldefined macromolecular architectures can be prepared. [32][33][34] The covalently linked triple block copolymers are now well recognized and used as an innovation strategy of molecular-based functional materials with a new molecular architecture.…”