Local Composition of Nanophase-Separated Mixed Polymer Brushes

Santer, Svetlana; Kopyshev, Alexey; Yang, Hee-dong; Rühe, Jürgen

doi:10.1021/ma060092y

Cited by 57 publications

(86 citation statements)

References 42 publications

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“…The morphology of the patterns depends strongly on both the molecular characteristics of the brush as well as external conditions such as quality of solvents to which the brush is exposed to. The same area on the polystyrene-poly(methyl methacrylate) (PS-PMMA) mixed brush can adopt different topographies ranging from flat (4) to patterned (1-3) (c) [28,29,30]. The chemical structure (d) of a PS-PMMA mixed brush is discussed in the text.…”

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“…It has been predicted theoretically and recently shown experimentally that the different topographies of a certain brush (with given molecular weight, grafting density, and the Flory-Huggins parameter of the polymers) depend on the quality of the solvent that the polymer system is exposed to. [22][23][24][25][26]29,30] It is furthermore possible to switch between two distinct morphologies over many cycles of solvent exchange. This phenomenon is being employed at present to create surfaces of adjustable hydrophobicity.…”

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“…2c and d). [29][30][31] We have carefully checked that the redistribution is not induced by other relevant processes, such as thermal diffusion or capillary forces, the impact of which have been addressed by additional experiments. Diffusion could be excluded by repeating the experiment on homopolymer brushes that do not show changes in topography when being exposed to different solvents: the particles stick to their initial positions.…”

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confidence: 99%

“…[31] The topographical changes result in redistribution of the polymers PS and PMMA on the top of the brushes. [29,30] It was shown that after treatment with acetone the surface of the brush consists of only PMMA chains, that is, the patterns have a "dimple"-like structure www.advmat.de Figure 2. Scheme of a mixed brush carrying a nanosphere (a).…”

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Dynamically Reconfigurable Polymer Films: Impact on Nanomotion

et al. 2006

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The idea of building motors or engines at nanometer dimensions that eventually could themselves manipulate structures of comparable size has grown along with the major breakthroughs in nanotechnology over the last 20 years. This mainly concerns manipulating nanometer-sized objects such as adsorbed macromolecules or nanometer-sized colloids directly using scanning force microscopy (SFM) techniques that first helped to give a closer look at the nanometer-scale world. Such simple mechanical methods still represent the most fruitful approaches for manipulation on the nanometer scale. [1][2][3][4][5][6][7][8] In a second line of research, attempts are made to construct nanometer-sized motors that are mostly based on natural complexes, mimicking and utilizing the peculiar properties of protein motors. [9][10][11][12][13] Both approaches are already optimized with respect to their specific field of application: for example, in the case of SFM, precise positioning of single colloids, molecules, and even atoms is possible, but manipulating ensembles of particles in parallel is a nearly intractable task. Protein motors such as kinesin microtubuli are highly efficient by their very nature, but only work in aqueous solutions and within a narrow temperature range where they can operate efficiently. Naturally, both approaches cannot cover all conceivable tasks that might emerge with the ongoing development of nanometer-scale science, such as parallel manipulation of nanometer-sized objects over large areas under a broad range of environmental conditions.Polymer systems in their diversity may offer a range of alternatives, especially in the form of suitably designed thin films. Recently, we have proposed to use the unique conformational properties of so-called polymer brushes to move nanometersized objects that are adsorbed on their top.[14] The brushes consist of polymer chains typically several hundreds of nanometers in length, with one end covalently attached to a solid substrate. [15][16][17] The distance between neighboring chains ranges from 0.5 to 5 nm. Such a high grafting density forces the flexible polymer chains to stretch away from the surface. [18,19] Particularly interesting are multicomponent brushes that consist of two or more different polymers, among which phase separation can occur (Fig. 1a). Such systems can be of two different types: i) brushes consisting of diblock or triblock copolymers covalently attached by one block type to a substrate and thus resulting in a variation in the composition along the chains, and ii) brushes made of a mixture of two homopolymers, each of which is attached to the surface, resulting in a lateral variation in composition. [20][21][22][23][24][25][26][27][28] Together with the restriction of the mobility due to grafting, the phase separation results in a topographical nanometer-scale pattern on the brush surface (Fig. 1b). The size, shape, and composition of these patterns depend on many parameters, such as molecular parameters of the attached chains, the surface free energy o...

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Dynamically Reconfigurable Polymer Films: Impact on Nanomotion

et al. 2006

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“…Covalently attached polymer layers, so called polymer brushes, offer enhanced stability over physisorption. [1][2][3][4][5][6] Moreover, grafting two incompatible polymers randomly on a surface prevents macroscopic phase separation but still allows nano-phase segregation into nanostructures. By controlling the chain architecture, grafting density, molecular lengths of polymer brush and individual components, and interaction energy between individual polymers, well-defined patterns with characteristic sizes and shapes can form, such as spherical inclusions, wormlike or flowerlike domains.…”

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Local chemical composition of nanophase-separated polymer brushes

Filimon

Kopf

Schmidt

et al. 2011

Phys. Chem. Chem. Phys.

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Using scattering scanning nearfield infrared microscopy (s-SNIM), we have imaged the nanoscale phase separation of mixed polystyrene-poly(methyl methacrylate) (PS-PMMA) brushes and investigated changes in the top layer as a function of solvent exposure. We deduce that the top-layer of the mixed brushes is composed primarily of PMMA after exposure to acetone, while after exposure to toluene this changes to PS. Access to simultaneously measured topographic and chemical information allows direct correlation of the chemical morphology of the sample with topographic information. Our results demonstrate the potential of s-SNIM for chemical mapping based on distinct infrared absorption properties of polymers with a high spatial resolution of 80 nm Â 80 nm.

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