The interaction between sulfate polystyrene latex and bilayer vesicles is d
escribed from the point of view of membrane-induced latex deflocculation an
d theoretical colloid stability for bilayer-covered particles from a DLVO m
odel without free parameters. Unilamellar cationic or anionic vesicles were
prepared from dioctadecyldimethylammonium bromide (DODAB) or asolecithin (
ASO), respectively, and allowed to interact with sulfate polystyrene micros
pheres of several sizes. Mean zeta-average diameters for latex particles in
the interacting mixtures decreases as a function of interaction time betwe
en sulfate polystyrene particles and asolecithin vesicles attaining a final
size compatible with a negatively charged asolecithin monolayer deposited
onto the anionic latex surface. In contrast to the ASO behaviour, the catio
nic DODAB was previously reported to deposit as a bilayer onto the sulfate
latex. The occurrence of an ordered amphiphile assembly deposited onto the
latex is highly dependent on the proportion of total surface areas for vesi
cles and particles. From zeta-potential measurements and a DLVO model, theo
retical colloid stabilities are calculated as a function of monovalent salt
concentration or particle size and found to be much higher than experiment
ally measured stabilities. DLVO expectations are not fulfilled in spite of
the presumably ideal nature of the bilayer-covered polystyrene microsphere
as a colloid. (C) 1999 Elsevier Science B.V. All rights reserved.