MACROMOLECULES IN ORDERED MEDIA .1. INTERFACIAL INTERACTIONS BETWEEN A CATIONIC POLYMER AND OPPOSITELY CHARGED LIPOSOMES

The incorporation of a cationic polymer, such as poly(4-vinylpyridine) , to the outer leaflet of negatively charged phospholipid vesicles of dimyristoylphosphatidic acid has been investigated by viscometry and i ntrinsic fluorescence. Viscosity changes of dilute solutions follow th e size of the polymer and the polymer-liposome complex. Variations in the emission spectrum of poly(4-vinylpyridine) upon the addition of li pid vesicles under different conditions give the amount of polymer bou nd per mole of accessible lipid. These experimental results have been interpreted by means of the Gouy-Chapman formalism, which calculates t he effective number of charges per polymer chain at the interface. The size of the adsorbed polyion has been computed from a discrete charge virial expansion that takes into account the mobility of charged grou ps at the interface.