Abrupt interfacial transitions of hydrophobic polysilanes as probed via liquid crystal-assisted stepwise deposition

The Langmuir-Blodgett deposition was applied for the first time for fully hydrophobic polysilanes, poly(di-n-hexylsilane) (PDHS) and poly(methyl-n-octylsilane) (PMOS). The monolayer formation of such hydrophobic polysilanes was achieved by cospreading with a liquid crystal molecule, 4'-pentyl-4-cyanobiphenyl (5CB). The UV-visible absorption spectra showed that the backbone conformations of the polysilanes are completely different from that in the bulk. The layer-by-layer deposition allowed for the nanometer level evaluation of the thickness profile on the conformational changes. It is found that the conformational change of these hydrophobic polysilanes abruptly occurs at a monolayer level thickness boundary.