Mixtures of solvents and mixtures of block copolymers as tools for tunable structures in block copolymer thin films

点击翻译按钮获取中文摘要

The continuation project aims at (i) understanding the processes in diblock copolymer thin films during vapor treatment with solvent mixtures and (ii) at using micro- and macrophase separation in thin films of mixtures of diblock copolymers to prepare complex structures. In project part (i), thin films from cylinder-forming diblock copolymers will be vapor treated with mixtures of selective and non-selective solvents. This will lead to an understanding of the restructuring processes; thus, optimum protocols to anneal defects and to induce the desired cylinder orientations by solvent vapor annealing will be identified. In project part (ii), thin films from binary mixtures of symmetric diblock copolymers will be investigated which form complex structures due to the interplay of micro- and macrophase separation. In mixtures of symmetric and asymmetric diblock copolymers, we will investigate the transition from the lamellar to the cylindrical morphology including possible interphases and epitaxial growth as well as the role of the film interfaces. Solvent vapor treatment will bring the samples into equilibrium. The poly(styrene-b-dimethylsiloxane) system will be chosen for all investigations because it is stable, has a high interaction parameter and because a number of solvents having different selectivity exist. In-situ, real-time grazing-incidence small-angle X-ray scattering will be combined with in-situ white-light interferometry and ex-situ atomic force microscopy and X-ray reflectometry. Selected samples will be investigated using time-of-flight neutron reflectivity to highlight the solvent distribution in the swollen films. The experimental studies will be supported by theoretical calculations and computer simulations by the Russian project partner. This way, we aim at furthering our understanding of structure formation in these multicomponent systems. The project is realized in the framework of the Memorandum of Understanding of the RFBR and DFG.