Polyelectrolyte adsorption layers studied by streaming potential and particle deposition.

Area of Science:

• Surface Science
• Colloid and Interface Science
• Polymer Science

Background:

• Understanding polyelectrolyte adsorption is crucial for surface modification and material design.
• Characterizing adsorbed polymer layers, especially their electrokinetic properties, presents challenges.

Purpose of the Study:

• To characterize the adsorption of polyallylamine hydrochloride (PAH) on mica surfaces.
• To correlate polymer coverage with surface electrokinetic properties and particle deposition behavior.
• To evaluate the utility of combined electrokinetic and particle deposition methods for detecting adsorbed polyelectrolytes.

Main Methods:

• Streaming potential measurements to determine apparent zeta potential.
• Deposition of negative polystyrene latex particles to assess surface coverage and deposition rates.
• Application of convective diffusion theory for data analysis.

Main Results:

• The apparent zeta potential of mica surfaces decreased with increasing polyallylamine hydrochloride (PAH) coverage.
• A direct correlation was found between PAH coverage and particle deposition rate and jamming coverage.
• Negative latex particle deposition was observed on surfaces with a negative apparent zeta potential, explaining previous anomalous findings.

Conclusions:

• The combined electrokinetic and particle deposition methods effectively detect adsorbed polyelectrolytes on surfaces.
• These methods allow for the measurement of bulk polyelectrolyte concentrations down to 0.05 ppm.
• The study provides a robust approach for characterizing polymer-surface interactions and detecting low-level polymer contamination.