| Abstract
| - The molecular organization of a cationic matrix (DOMA) as influenced by the presence of an anionic water-soluble porphyrin (TSPP), in the mixed monolayer, molar ratio TSPP/DOMA = 1:4, has been studied byπ−A isotherms, the reflection spectra, BAM images, and imaging ellipsometry at the air−water interface. Areversible collapse of the mixed film at high surface pressures is observed. The formation of an aggregate ofthe porphyrin molecules under compression is inferred from the reflection spectra. BAM images show thespontaneous formation of domains at 35 mN/m that become bigger during the spontaneous dense process atconstant surface pressure. The reversible character of that process was also observed by BAM. The evaluationof the reflection spectra as well as the area fraction of the domains and the surrounding dark regions have ledus to consider a trilayer structure for the TSPP/DOMA domains emerging during the collapse process. Byusing imaging ellipsometry on selected regions of interest (few microns), the thicknesses of domains (ddom =5.045 nm) and surrounding areas (ddark = 1.764 nm) were estimated. These thickness values are in goodagreement with the trilayer architecture where the DOMA molecules have retained the TSPP molecules byelectrostatic interactions.
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