Rearrangements of Metastable Micelles to Different Molecular Bilayers on Planar Graphite, Mica, Silicon, and Hydrocarbon Surfaces

Abstract

Bis(2,2‘-bipyridyl)(dihexadecyl-2-[2,2‘-dipyridylmethylene] malonate) ruthenium(II) dihexafluorophosphate, 1, formed multilayered micelles (denoted C16-micelles) upon sonication of aqueous suspensions. The C16-micelles collapsed upon transfer to gold, mica, and silicon surfaces and rearranged to planar bilayers. These bilayers appeared in different arrangements under the atomic force microscope. On graphite, the ruthenium headgroups and the alkyl chains lay flat and were both in direct contact with the substrate. On mica and silicon wafers, upright-standing interdigitated bilayers were found exclusively. Self-assembly of a dodecylsilane layer containing cracks on the silicon surface induced the formation of irregular double and triple layers of 1. Bulk polyethylene or octadecylthiol layers on gold with smooth surfaces did not disrupt the micelles. C18- and C22-micelles made of the corresponding homologues of 1 were much more stable on most surfaces, C14-micelles were destroyed on all surfaces. The variability of micelle−substrate interactions is discussed qualitatively.