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Authors
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Ionov, L. ; Sidorenko, A. ; Stamm, M.
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Title
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Gradient Mixed Brushes: "Grafting To" approach
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Date
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31.12.2004
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Number
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12315
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Abstract
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External stimuli, such as light, solvent, pH, or an electric field, allow for a fine-tuning of the surface properties of specially designed responsive polymer materials.1-6 This behavior can be used for regulation and switching of wetting behavior, adhesion, adsorption, etc.7-9 An important example of the stimuli responsive surfaces is represented by mixed polymer brushes consisting of two or more incompatible polymers grafted to the same substrate. Successful synthetic methods for mixed polymer brushes via “grafting to” and “grafting from” approaches were recently reported.10-13 Theoretical and experimental studies gave evidence that the mixed brushes undergo phase transition upon external stimuli. The properties of the thin brushlike film depend on the balance between layered and lateral phase segregation mechanisms.14-19 Selective solvents (good solvent for one of two grafted polymers) stabilize a dimplelike morphology:· an unfavorable polymer forms clusters that are segregated to the grafting surface while the favorite polymer forms a discontinuous phase preferentially segregated to the brush surface (a top layer). In nonselective solvents, lateral segregation dominates and the mixed brushes form a ripplelike morphology:· lamellar-like stripes are formed by alternating microphases of both polymers. In the latter case, both polymers are present on the surface in an equimolar ratio if the mixed brush is symmetrical (1:1 of both polymers). An increase in the compositional asymmetry of the mixed brushes, or an increase in incompatibility, results in dimple phases.17 Thus, the morphology of the brush is a function of the composition and interactions with solvent.
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Publisher
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Macromolecules
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Wikidata
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Citation
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Macromolecules 37 (2004) 7421-7423
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DOI
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https://doi.org/10.1021/MA049147R
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Tags
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polymer brushes gradual variation anchoring layer surfaces
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