Reversible sphere-to-lamellar wetting transition at the interface of a diblock copolymer system
We use ellipsometry to investigate a transition in the morphology of a sphere-forming diblock copolymer thin-film system. At an interface the diblock morphology may differ from the bulk when the interfacial tension favours wetting of the minority domain, thereby inducing a sphere-to-lamella transition. In a small, favourable window in energetics, one may observe this transition simply by adjusting the temperature. Ellipsometry is ideally suited to the study of the transition because the additional interface created by the wetting layer affects the polarisation of light reflected from the sample. Here we study thin films of poly(butadiene-ethylene oxide) (PB-PEO), which order to form PEO minority spheres in a PB matrix. As temperature is varied, the reversible transition from a partially wetting layer of PEO spheres to a full wetting layer at the substrate is investigated.
- 26.In order to obtain the sphere radius, we used the strong-stretching theory expression for domain size as described by Matsen and Bates bates1997 with experimental parameters for the sphere radius and volume fractions given for an equivalent system by similar system by Huang and co-workers .Google Scholar
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