Charge Formation on Polymer Surfaces
The zeta potential is one of the most sensitive indicators to monitor effects of activation and contamination of polymer surfaces.
Polymers play a dominant role in various fields of present-day technologies. Their applications range from plastic bottles and bags, packaging and containers, automotive, man-made fibers to membranes, biomaterials and electronics.
Common to any untreated polymer surface is its water repulsion known as the degree of “hydrophobicity”. This surface property affects the mechanism of charge formation on the polymer surface.
In the presence of an aqueous solution, an “inert” polymer surface becomes negatively charged due to the preferential adsorption of hydroxyl ions (OH-) as compared to hydronium ions (H3O+) at similar concentration.
This characteristic “polymer-like” behavior can be followed by the change in zeta potential, based on streaming current or streaming potential measurement.
The negative zeta potential of inert polymer surfaces like poly(methyl methacrylate), PMMA, and poly(ethylene terephthalate), PET decreases towards lower pH and passes through the isoelectric point (IEP) at pH 4.
The very sensitive streaming potential / streaming current measuring technique is unique to monitor polymer activation by surface treatment and to determine surface contamination of polymers.
R. Zimmermann, S. Dukhin, C. Werner, J. Phys. Chem. B 105 (2001) 8544-8549