For cationic amphiphiles with long alkyl double chains, The results of contact angle measurements on polystyrene (PS) a pronounced counterion specificity has been observed for or poly(styrene/methacrylate) (PSMA) surfaces with aqueous diintra-and interlayer interactions ( 5 -9 ) . The smaller the octadecyldimethylammonium bromide (DODAB), chloride (DOhydrated anion, the more contracted the monolayer com-DAC), or acetate (DODAc) dispersions in the range 10 06 -10 04 pression isotherm becomes ( 6 ) . In accordance with this M are reported. At each concentration two separate angles were strong repulsive intralayer force that causes expansion in measured: initial advancing (A) and initial receding (R). For the the dihexadecyldimethylammonium acetate ( DHDAA ) polystyrene surface without charge, A and R decreased as a funcair / water monolayer and interdigitation in the bilayer, a tion of amphiphile concentration (C) for all surfactants. For the short-ranged hydration repulsion between layers develops charged copolymers, A and R first increased and then attained a plateau value as a function of C. In the presence of DODAB, as depicted from measurements using the osmotic stress DODAC, and DODAc dispersions, constant contact angles attechnique ( 9, 10 ) . Cationic vesicles composed of dioctadetained on the PSMA surface with the highest charge density were cyldimethylammonium chloride or bromide interact with 85, 72, and 67 degrees, respectively. In this case, hysteresis, which oppositely charged polystyrene microspheres. First, one is generally very large for soluble surfactants, was absent. Counterbilayer is deposited onto the latex ( 11 ) . Thereafter, as ions effect on the nature of the deposited surfactant layer is to surfactant concentration increases, vesicles adhere to the increase hydrophilicity according to acetate ΓΊ chloride ΓΊ bromide. covered latex with or without disruption, depending on the For pure polystyrene, amphiphile molecules lie on the hydrophobic surfactant counterion ( 11 ) .
homopolymer. In contrast, increasing the surface charge on the
In this work, the interaction between cationic vesicles and polymer surface promotes a high degree of vertical orientation of polymers is further investigated from the contact angle point the hydrocarbon chains.