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Simultaneous Tuning of Chemical Composition and Topography of Copolymer Surfaces: Micelles as Building Blocks
Author(s) -
Zhao Ning,
Zhang Xiaoyan,
Zhang Xiaoli,
Xu Jian
Publication year - 2007
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200700032
Subject(s) - copolymer , micelle , chemical composition , chemical engineering , materials science , chemistry , composition (language) , nanotechnology , polymer , organic chemistry , aqueous solution , linguistics , philosophy , engineering
A simple method is described for controlling the surface chemical composition and topography of the diblock copolymer poly(styrene)‐ b ‐poly(dimethylsiloxane)(PS‐ b ‐PDMS) by casting the copolymer solutions from solvents with different selectivities. The surface morphology and chemical composition were characterized by scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS), respectively, and the wetting behavior was studied by water contact angle (CA) and sliding angle (SA) and by CA hysteresis. Chemical composition and morphology of the surface depend on solvent properties, humidity of the air, solution concentration, and block lengths. If the copolymer is cast from a common solvent, the resultant surface is hydrophobic, with a flat morphology, and dominated by PDMS on the air side. From a PDMS‐selective solvent, the surface topography depends on the morphology of the micelles. Starlike micelles give rise to a featureless surface nearly completely covered by PDMS, while crew‐cut‐like micelles lead to a rough surface with a hierarchical structure that consists partly of PDMS. From a PS‐selective solvent, however, surface segregation of PDMS was restricted, and the surface morphology can be controlled by vapor‐induced phase separation. On the basis of the tunable surface roughness and PDMS concentration on the air side, water repellency of the copolymer surface could be tailored from hydrophobic to superhydrophobic. In addition, reversible switching behavior between hydrophobic and superhydrophobic can be achieved by exposing the surface to solvents with different selectivities.