Light-Directed Anisotropic Reorientation of Mesopatterns in Block Copolymer Monolayers

Photoreorientation of a stripe pattern consisting of an MPS structure in a Langmuir‐Blodgett monolayer by irradiation with linearly polarized light is achieved for the first time using a PDMS/poly(methacrylate) diblock copolymer with a liquid crystalline azobenzene‐containing side chain. The stripe MPS pattern in the trans azobenzene state is diminished by photoisomerization to the cis form upon UV light irradiation. By the erasure of the MPS structure, the anisotropic photo‐oriented stripe pattern is generated upon irradiation with linearly polarized visible light, the orientation of the stripe pattern being orthogonal to the electric vector of the light. Photo‐reorientation of a stripe‐pattern of microphase separation (MPS) structure in a Langmuir‐Blodgett monolayer by irradiation with linearly polarized light is achieved for the first time using a diblock copolymer consisting of poly(dimethylsiloxane) (PDMS) and poly(methacrylate) with a liquid‐crystalline azobenzene‐containing side chain. The key to the anisotropic morphology control is the involvement of the erasure step in the photoprocess.