Liquid‐Crystalline Polymer with a Block Mesogenic Side Group: Photoinduced Manipulation of Nanophase‐Separated Structures

Abstract

In this report, a novel type of photoresponsive liquid crystalline polymer with a block mesogenic side‐group is demonstrated. The block mesogene is an amphipathic molecule containing a hydrophobic mesogene (azotolane moiety) and hydrophilic oligooxyethylene moieties in the same unit. The block mesogene in the polymer plays a role in liquid crystalline, amphiphilic and photoresponsive properties. As expected, a film prepared from the polymer exhibits phase separation of a lamellar structure due to cooperative motion between liquid crystal assembly and nanophase separation. The morphology of the lamellae can be aligned upon irradiation of linearly polarized light. Moreover, a photochemical phase transition induced by unpolarized UV irradiation erases the surface morphology. The erased nanostructure can be recovered by annealing or irradiation of linearly polarized light, meaning that the surface morphology is rewritable via a photochemical process.

Light‐Directed Anisotropic Reorientation of Mesopatterns in Block Copolymer Monolayers

“…The Az polymer block in the cis‐ form probably provides the similar situation. Okano et al18 recently reported the erasure of nano‐morphology by UV light irradiation in a film of a homopolymer possessing Az and oligo(ethylene oxide) block in the side chain. Our observation involves the erasure of the MPS morphology originated from the main chain of the polymer.…”

“…b b Okano et al18 recently reported the photoalignment of a stripe morphology for a thin film directing preferentially ‘parallel’ to LPL. The difference arises from the polymer architecture.…”

Photoinduced Microphase Separation in Block Copolymers: Exploring Shape Incompatibility of Mesogenic Side Groups

“…In all these studies, BCPs were microphase-separated before illumination and light was used either to change the morphology, or to induce ordering or pattern different alignments of nanocylinders. [2][3][4][5][6] To the best of our knowledge, no photoinduced microphase separation in a BCP has been achieved thus far. Herein we report the first example.…”

“…Kadota et al [5] showed that the photoisomerization could change the morphology of a Langmuir-Blodgett monolayer film. Okano et al [6] synthesized a liquid crystalline polymer with an azo block mesogenic side group and showed that the photoisomerization could erase the lamellar morphology formed due to microphase-separated block side groups. In all these studies, BCPs were microphase-separated before illumination and light was used either to change the morphology, or to induce ordering or pattern different alignments of nanocylinders.…”

Meso‐ and Microscopic Motions in Photoresponsive Liquid Crystalline Polymer Films

“…Another type of polymer architecture was reported by Okano et al They synthesized a series of LC homopolymers in which a “nanophase separation” occurs within the side chain (Table , 20 ). The side chains were composed of a hydrophobic azobenzene part and a hydrophilic oligo(ethylene oxide) part in the tail.…”