STABILITY OF DIMETHYLDIOCTADECYLAMMONIUM BROMIDE MONOLAYERS ON CLEAVED MICA IN WATER AND AT THE AIR WATER INTERFACE/

The wettability and structure of Langmuir-Blodgett monolayers of dimet hyldioctadecylammonium bromide (DMDOA) on mica are affected by partial dip in water. After Gh of clipping, high hydrophilicity was observed at the boundary between the dipped and undipped regions. Atomic force microscopic images of this sample have shown a bare mica surface in th e boundary region. The hydrophilicity is due to this exposure of the m ica surface. From the fact that the three-phase (air/water/sample surf ace) contact line (TPL) moved slowly (much less than 20 mu m/s) in the boundary region during the dipping, it was concluded that the slow mo vement of TPL stimulates the release of DMDOA molecules. The structure of the monolayer in the boundary region is also dependent on the velo city of TPL movement. In water, we found rearrangement of the DMDOA mo lecules via migration on mica and/or re-adsorption.