Drastic Change in Orientation of Cylindrical Microdomains Upon Thermal Annealing in Thin Film of Block Copolymer Having Liquid Crystalline Moiety

We found a drastic change in orientation of cylindrical microdomains from perpendicular to parallel with respect to the film surface by thermal annealing for a liquid crystalline diblock copolymer, PEO122-PMA(Az)(50), consisting of poly(ethylene oxide) (PEO) and poly(methacrylate) with the side chain of a liquid crystalline azobenzene moiety. Non-contact mode AFM (atomic force microscopy) is used to observe the orientation of cylinders on the surface of the film specimen. Perpendicular orientation of the PEO cylinders for the as-spin-coat specimen is found to change drastically to the parallel orientation as a function of the thermal annealing time at 140 degrees C. It is interesting to find inclined cylinders in the course of the transition. Grazing-incidence small-angle X-ray scattering is also conducted to analyze the cylinder orientation in the interior of the specimen. As a result, the parallel orientation of the PEO cylinders is found even for the case when the inclined cylinders are detected by AFM on the surface of the film specimen.