Modification of polymers by adsorption phenomena

Abstract

The adsorption of ions and amphiphilic molecules on solid polymers is investigated by direct force measurements using an atomic force microscope (AFM). It is shown that electrolyte ions are changing the surface potentials of the solid polymers as well as their adhesive properties. The experiments show that the interaction with a negatively charged probe is dramatically decreased by the adsorption of anions. The adsorption isotherms are determined by zeta potential measurements (streaming potential of flat plates). In presence of adsorbing anions, the attractive interaction and the adhesion are reduced and can be eliminated completely. So, even solutions of simple electrolyte ions can be applied intentionally in order to modify the interaction of polymer surfaces. A wide variety of technological applications becomes accessible.

Laterally Resolved Measurement of Interaction Forces between Surfaces That Are Partly Covered with Polyelectrolytes

“…At small distances it should always exceed the double layer force. However, it is important to note here that the adsorption of electrolyte ions reduces the attractive interaction and the adhesion might be completely eliminated (63). Comparing the measured force vs distance functions with calculated curves according to the DLVO theory allows us to determine important parameters such as Debye length, interfacial potentials, or the Hamaker constant.…”

Influence of Aqueous Electrolytes on the Wetting Behavior of Hydrophobic Solid Polymers—Low-Rate Dynamic Liquid/Fluid Contact Angle Measurements Using Axisymmetric Drop Shape Analysis

“…As found by Weidenhammer et al (5) ion adsorption may change the adhesive properties of polymers. Up to now, less attention has been paid to the effect of electrolyte ions (ion concentration, pH) on interfacial tension and wetting behavior (contact angle).…”

“…A recent publication by Ninham and Yaminsky (4) has pointed out that ion adsorption due to dispersion forces must not be neglected because it influences many phenomena in colloid and surface science. Electrolyte ions are e.g., the origin of the zeta potentials at solid polymers (5,6). Even if the polymer surface does not contain a native surface charge, it may however be charged in an aqueous electrolyte solution by the preferential adsorption of anions or cations, respectively.…”

Adsorption Processes at Solid Surfaces-Studied by Electrokinetic Investigations

“…Further raise of ion concentration causes the contraction of the double layer and with it the zeta potential decreases. In different papers this point of ζ max was verified by direct force measurements [12,13]. Fig.…”