Orientations of Liquid Crystals in Contact with Surfaces that Present Continuous Gradients of Chemical Functionality
| Autor: | Kirill Efimenko, Daniel A. Fischer, Nicholas L. Abbott, Jan Genzer, Brian H. Clare |
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| Rok vydání: | 2006 |
| Předmět: | |
| Zdroj: | Chemistry of Materials. 18:2357-2363 |
| ISSN: | 1520-5002 0897-4756 |
| DOI: | 10.1021/cm052537n |
| Popis: | We report the formation of continuous spatial gradients in the density of grafted semifluorinated chains on silicon oxide surfaces by vapor-phase diffusion of semifluorinated silanes. We quantify the orientations of the nematic liquid crystal (LC) 4-cyano-4‘-pentylbiphenyl on these surfaces as a function of local surface composition obtained by using NEXAFS. These measurements demonstrate that it is possible to obtain the full range of tilt angles of a LC on these surfaces. We also use the data provided by these gradient surfaces to test hypotheses regarding the nature of the interaction between the LC and surfaces that give rise to the range of tilted orientations of the LC. We conclude that the orientations of the LC are not determined solely by the density of grafted semifluorinated chains or by the density of residual hydroxyl groups presented at these surfaces following reactions with the silanes. Instead, our results raise the possibility that the tilt angles of the semifluorinated chains on these s... |
| Databáze: | OpenAIRE |
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