Wedge-shaped molecules with a sulfonic group at the tip have been incorporated into a poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) diblock copolymer via proton transfer at different degrees of neutralization. The protonation of P2VP was monitored by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The thin film morphology of the complexed block copolymers has been studied by scanning force microscopy and X-ray reflectivity. The complexes exhibit strongly microphase-segregated patterns comprising smectic layers of the complexed P2VP blocks, oriented parallel to the substrate throughout the whole film with the embedded PEO domains. For the complex with a degree of neutralization of 0.50 ordered amorphous PEO cylinders are observed oriented perpendicular to the substrate. For a degree of neutralization equal to 0.25 initially also perpendicular PEO cylinders are formed, but upon solvent-vapor annealing they partially merge, resulting in a mixed lamellar-cylindrical morphology. In all cases an extra surface layer is formed at the substrate. Thus, for the first time we have demonstrated that a block copolymer thin film structure can easily be controlled by the degree of neutralization of one of the blocks.

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Journal Macromolecules
Albrecht, K, Mourran, A, Zhu, X, Markkula, T, Groll, J, Beginn, U, … Möller, M. (2008). Thin film morphologies of block copolymers complexed with wedge-shaped liquid crystalline amphiphilic molecules. Macromolecules, 41, 1728–1738. doi:10.1021/ma071317n