ELLIPSOMETRIC AND FLUORESCENCE MICROSCOPIC INVESTIGATIONS OF A CYCLAM DERIVATIVE AT THE AIR-WATER-INTERFACE

In this study, a cyclam derivative bearing four aliphatic chain substituents shows, as many amphiphiles, liquid-expanded as well as solid phases. In contrast to the classical amphiphiles, the pi-A isotherm shows a bumplike shape at the beginning of the phase transition for which the amplitude is a function of the compression speed. Ellipsometry, which is very sensitive to the monolayer physical state changes, and fluorescence microscopy, which has contributed significantly to the understanding of the phenomena occurring in the phase transition region, have been used to investigate the monolayer behavior of N,N',N'',N'''-tetramyristoyl-1,4,8,11-tetraazacyclotetradecane at the air/water interface. This study shows that in the liquid-expanded state, independent of the compression speed, the film is homogeneous and remains as such until either the maximum amplitude of the bump is reached or the beginning of the plateau sets in. Thereafter, the phase transition and solid state show domains for which the sizes, shapes, and orientation are dependent upon the compression speed. Homogeneous diamondlike shape domains with preferred orientation appear at low compression speeds (1.0 and 3.5 angstrom2/(molecule.min)) whereas random orientation of heterogeneous domains prevails at higher compression rates (greater-than-or-equal-to 7 angstrom2/(molecule.min)). Ellipsometric measurements are also characterized by their dependence upon the compression rates that change the optical properties of the surface. Increased light intensity at compensation is explained with surface anisotropy.