HYDRODYNAMIC THICKNESS OF INTERFACIAL LAYERS OBTAINED BY ADSORPTION OF A CHARGED DIBLOCK COPOLYMER ON A SELECTIVE SURFACE FROM AQUEOUS-SOLUTIONS

The solution properties of the asymmetric diblock copolymer poly(styre nesulfonate)-poly(vinylpyridine) were investigated using light scatter ing, viscometry, and fluorescence probing. Adsorption on neutral and e lectrically charged (selective sorbent) materials was determined using radiolabeled polymer, and the hydrodynamic thickness of adsorbed laye rs was measured by quasi-elastic light scattering measurements. In wat er, the copolymer displayed dual hydrophobic properties. Its strongest hydrophobic character, responsible for adsorption on the neutral mate rial poly(tetrafluoroethylene) (Teflon), was abolished by addition of very small amounts of electrolyte, while the volume of the less hydrop hobic moieties was pH dependent. The solubility domain of the copolyme r was limited to the pH range between 2.5 and 3.8 and an ionic strengt h of less than 0.01. Micelles formed in water or 0.001 M NaCl solution showed a maximum value of the radius of gyration close to 220 nm. Par tially reversible adsorption on positively charged polystyrene latex p articles bearing amidine surface groups could involve both hydrophobic and ionic interactions, while the hydrodynamic thickness of the resid ual interfacial layer after rinsing with solvent was dependent on the initial copolymer concentration in the supernatant phase and on the pH and electrolyte concentration of the final suspending phase. The adso rbed copolymer layer appeared to be well suited to the stabilization o f colloids in electrolyte media due to its electrosteric protective ef fect, which increased with electrolyte concentration.