Linear dichroism investigations of the surface-pressure-induced phase transitions in surface-active dimethylaminobenzylidene 1,3-indandione Langmuir and Langmuir-Blodgett films

Molecular structure and optical properties of the novel amphiphilic derivative of dimethylaminobenzylidene 1,3- indandione (C17DMABI), have been studied as the monolayer on a water surface (Langmuir films) and Langmuir-Blodgett (LB) multilayers of Y-type structure using optical absorption techniques. The compression (pi) - A isotherms of the C17DMABI monolayer show two different phases. Phase transition takes place at surface pressures 1 less than (pi) less than 20 mN/m. The compression-induced changes of the monolayer spectra in the region 330 - 600 nm have been analyzed using deconvolution of spectra of Gaussian shaped bands. At least three different transitions takes place at approximately 395, approximately 445 and approximately 505 nm. Analysis of deconvoluted band spectral shifts, intensities and dichroism confirms a molecular packing rearrangement and change of the tilting angle at the phase transition pressure interval.