Tunable morphologies in charged multiblock polymers in thin film geometry

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The research project addresses the morphologies formed by multiblock polymers of the type ABCBA in thin film geometry. At this, a pentablock terpolymer featuring hydrophobic poly(methyl methacrylate) (PMMA) end blocks A together with poly(2-(dimethylamino)ethyl methacrylat) (PDMAEMA) and poly(2-vinylpyridine) (P2VP) middle blocks B and C will be investigated. The charge state of the PDMAEMA and P2VP blocks can be controlled by the pH value of the solution used for preparation of the films and has a strong influence on the structures in the film. Aim of the project is to use cyclic vapor treatment with selective solvents (water, methanol) to install a multitude of morphologies, which are a result of the interplay between the interactions between the blocks and the bridging of the nanodomains. The films are prepared by spin-coating from aqueous solution having different pH values. By taking up solvent, the mobility of the end blocks as well as the flexibility of the middle blocks will be altered, which possibly results in equilibrium states and enables the mixing of different blocks. The film morphologies will be investigated, also in situ, using optical microscopy, atomic force microscopy and grazing-incidence small-angle X-ray scattering (GISAXS). Modeling of the GISAXS data will be carried out using not only structures inside the film, but also contributions from the surface topography. Selected sample will be investigated using grazing-incidence resonant soft X-ray scattering, also during solvent vapor treatment, to discriminate the chemically different nanodomains. To elucidate the role of the sequential distribution of charges in the pentablock terpolymer, single measurements will be carried out on a reference sample PMMA-b-PDMAEMA-b-PMMA. The unique combination of a complex polymer, advanced in-situ methods for structural investigations and quantitative modeling will provide comprehensive insight into the behavior of multiblock polymers with charged blocks and the possibilities for structuring thin films.