Three sets of a new class of low surface tension block copolymers were synthesized consisting of a poly(dimethylsiloxane) (PDMS) block and a poly(perfluorooctylethyl acrylate) (AF8) block. The polymers were prepared using a bromo-terminated PDMS macroinitiator, to which was attached an AF8 block grown using atom transfer radical polymerization (ATRP) in such a designed way that the molecular weight and composition of the two polymer blocks were regularly varied. The interplay of both the phase separated microstructure and the mesomorphic character of the fluorinated domains with their effect on surface structure was evaluated using a suite of analytical tools. Surfaces of spin-coated and thermally annealed films were assessed using a combination of X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) studies. Both atomic force microscopy (AFM) measurements and grazing incidence small angle X-ray scattering (GISAXS) studies were carried out to evaluate the microstructure of the thin films. Even in block copolymers in which the PDMS block was the majority component, a significant presence of the lower surface energy AF8 block was detected at the film surface. Moreover, the perfluorooctyl helices of the AF8 repeat units were highly oriented at the surface in an ordered, tilted smectic structure, which was compared with those of the bulk powder samples using wide-angle X-ray powder diffraction (WAXD) studies. © 2011 The Royal Society of Chemistry.
|Original language||English (US)|
|Journal||Journal of Materials Chemistry|
|State||Published - 2011|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We are grateful to Dr B. Gallot (CNRS-Vernaison, France) for assistance with WAXD measurements, Dr D.-M. Smilgies (Cornell High Energy Synchrotron Source) for assistance with GISAXS studies, and Dr J. Shu (Cornell Center for Materials Research) for acquiring the XPS spectra. The authors thank the Italian MiUR (fondi PRIN 2008) for financial support of the work (GG). Support was also provided by the U.S. Department of Defense's Strategic Environmental Research and Development Program (SERDP), grant WP #1454 with additional support from the Office of Naval Research (ONR) through award N00014-02-1-0170 (CKO). Partial support from the Cornell KAUST Center and the Army Research Office Grant W911NF-05-1-0339 is also acknowledged (SK). Use of the National Synchrotron Light Source (Brookhaven National Laboratory) was supported by the U.S. Department of Energy, Office of Basic Energy Sciences. CHESS is supported by the National Science Foundation.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.