LATERAL DIFFUSION STUDY OF AMPHIPHILES IN AIR-WATER MONOLAYER FILMS OF POLYMERIZABLE SURFACTANTS

The behavior of the chromophore nyl)dipalmitoyl]-L-alpha-phosphatidyle th-anolamine (pyrene-DPPE) embedded in unpolymerized and polymerized a ir-water monolayers of 10,12-nonacosadiynoic acid (diacetylene 16-8), octadecyl methacrylate (ODMA) and (octadecyldimethylammonio)ethyl meth acrylate bromide (ODAEMA), has been investigated by using surface pres sure-area isotherm measurements, and steady-state and time-resolved fl uorescence spectroscopy. Steady-state fluorescence measurements reveal ed pyrene-DPPE to be homogeneously distributed in the diacetylene 16-8 monolayer only in the liquid-expanded (LE) phase on an alkaline subph ase. The lateral diffusion coefficients determined for the unpolymeriz ed diacetylene 16-8 monolayer from steady-state measurements are in go od agreement with literature values. Polymerization of the diacetylene 16-8 monolayer resulted in the formation of a liquid-condensed phase film and aggregation of pyrene-DPPE in the monolayer film, thus preven ting a fluorescence quenching study. Pyrene-DPPE was found to be aggre gated in both the monomer and polymer monolayers of ODMA. A derivative of ODMA incorporating a quaternary ammonium group (ODAEMA) was synthe sized. ODAEMA showed LE isothermal behavior and gave a homogeneous dis tribution of pyrene-DPPE in the monomer monolayer film. The lateral di ffusion coefficients obtained in the unpolymerized ODAEMA monolayer fi lm were found to decrease with increasing surface pressure, reflecting a decrease in monolayer fluidity with compression. In the polymerized film of ODAEMA, nonexponential fluorescence decay behavior of pyrene- DPPE was observed. The fluidity of the polymerized ODAEMA monolayer is estimated to be at least 1 order of magnitude less than that for the corresponding monomer monolayer.