MORPHOLOGICAL-CHANGES OF MONOLAYERS OF 2 POLYMERIZABLE PYRIDINE AMPHIPHILES UPON COMPLEXATION WITH CU(II) IONS AT THE AIR-WATER-INTERFACE

The monolayer behavior of two amphiphilic, diacetylenic units containi ng pyridine Ligands at the air-water interface is studied by measuring the surface pressure-area isotherms and by Brewster angle microscopy( BAM). Both amphiphiles form stable monolayers at the air-water interfa ce. The amphiphile containing an ester group shows a well-defined liqu id-expanded (LE) to liquid-condensed (LC) phase transition, while the amphiphile with the amide group forms only a condensed monolayer film at 9.4 degrees C. For both amphiphiles, addition of CuCl2 to the subph ase causes an increase of the surface pressure (IIc) at which the phas e transition appears, suggesting the formation of a coordination compl ex at the air-water interface. Addition of Cu(ClO4)2 to the subphase i nstead of CuCl2 causes an even larger increase in IIc, indicating that more copper ions bind to the monolayer which results in a more charge d monolayer. On a pure water subphase, Brewster angle microscopy of th e monolayer of the ester-containing ligand shows the formation of spir al dendritic crystalline domains at the plateau in the isotherm near t he solid state region. The formation of spiral crystalline domains ind icates that the LC phase is L-1'. The amide-containing ligand, however , forms two-dimensional crystalline domains directly after spreading a t the air-water interface, which are pushed together upon compression. No chiral crystalline domains were observed for this amphiphile indic ating that the ester and amide amphiphile have a different LC phase. B oth amphiphiles spread uniformly when the subphase contains CuCl2, and upon compression crystalline domains are formed which grow when the a rea per molecule is reduced further, until a condensed monolayer film is formed. The shape of the crystalline domains on a Cu(II) ion contai ning subphase changes by replacing the Cl- counterion by a ClO4(-) ani on. The size of the crystalline nuclei decreases when the Cu(II) conce ntration increases.