ИСТИНА

The interaction of polyelectrolytes with surfaces of various substrates is of considerable interest due to numerous important industrial applications of such polymers (e.g., for waste water treatment, paper processing, production of functional polymeric coatings, etc.). The use of model substrates whose surface properties can be rather easily varied in a relatively large scale opens a possibility to study this process in a systematic manner. In this contribution, the interaction between the cationic polyelectrolytes, poly(N-ethyl-4-vinylpyridinium bromide - co - 4-vinylpyridine)s with different contents of N-ethyl-4-vinylpyridinium units, and the model substrates, the multilayer films built up from amphiphilic derivatives of the alternating copolymers of maleic acid and olefines (ethylene, propylene) by means of Langmuir-blodgett (LB) technique is considered. The transformations of absorbance spectra of the LB films and quenching of fluorescence of pyrenyl labels covalently attached to one of the amphiphilic polymers forming such macromolecular assemblies were detected after their contact with dilute aqueous solution of the cationic polyelectrolytes. The observed changes were attributed to the adsorption of the positively charged macromolecules onto the LB films. The efficiency of this process was found to be rather sensitive to variations in pH of the surrounding medium as well as to the content of chraged units in macromolecules of the cationic polyelectrolytes. The amount of the adsorbed positively charged macromolecules was highest at pH > 8 where the LB films demonstrate high negative zeta-potential whereas the adsorption of the cationic polyelectrolytes become weaker upon decreasing pH, the efficiency of this process being observed to fairly correlate with zeta-potential of the LB films. For the cationic polyelectrolytes with higher contents of the charged units, the amounts of the adsorbed positively charged macromolecules were measured to be smaller than those obtained for the cationic polyelectrolytes with lower contents of the charged units. A comparative analysis of the data obtained by means of absorbance and fluorescence techniques suggests tha conformation of positively charged macromolecules adsorbed onto the LB films is not flat but rather coiled.