College Park, Maryland June 6 - 10 , 2004
MP8: Electric field alignment of asymmetric diblock copolymer thin films
Ting Xu, Thomas P. Russell (Department of Polymer Science and Engineering, University of Massachusetts, Amherst)
Electric fields alignment of asymmetric diblock copolymer thin films, polystyrene-block-poly(methyl methacrylate), was studied using small angle neutron scattering (SANS) and transmission electron microscopy (TEM). Starting from a poorly ordered state (as cast), surface fields and opposed electric fields biased the cylindrical microdomain orientation. With time upon annealing, the cylinders are locally disrupted to form ellipsoidal shape microdomains that connected into cylindrical microdomains in the applied field direction. Starting from an ordered state with cylinders parallel to the surface, the applied electric field enhanced fluctuations at the interfaces of the microdomains and disrupted cylindrical microdomains into spherical microdomains. This transition is similar to thermoreversible cylinder-to-sphere order-order transition. With time, the spheres deformed into ellipsoids and reconnected forming cylindrical microdomains oriented at ~45o with respect to the applied field. The tilted cylinders subsequently aligned along the applied field direction. This reorientation process is much slower than that from poorly ordered state.
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