Spreading behavior of polymerizable monolayers of acrylamides with double alkyl chains and polymerization of the LB films

Abstract

The spreading behavior of N, N'-dialkylacrylamide (dAAs) monomers on a water surface is investigated by measurement of surface pressure-area isotherms as a function of alkyl chain length and temperature. The monolayers of dAAs can be classified into three types. (I) N, N'-dioctadecylacrylamide (dODA) shows a rapid increase in surface pressure indicating formation of a rigid condensed monolayer; (II) the isotherm of N, N'-dihexadecylacrylamide (dHDA) has a plateau region in surface pressure corresponding to a phase transition from a expanded form to a condensed form, which corresponds to gel-liquid crystal phase transition often observed in biomembranes; and (III) the dialkylacrylamides with alkyl chain length shorter than the hexadecyl group form expanded monolayers with no condensed monolayer at any temperature. The similar three kinds of monolayers are also observed in the isotherms for dHDA monolayer as a function of temperature. It is found that two carbon elongation in double alkyl chains causes the same effect on the monolayer induced by about 10 °C cooling. Under various conditions, only liquid condensed monolayers are transferred on to a solid support, yielding the monomer LB films, practically, of dODA at any temperature and dHDA at low temperature. The polymerization of those LB films by UV irradiation was ascertained by the electronic absorption spectra.