Large apparent interfacial slippage at polyelectrolyte-perfluorocarbon interfaces on a quartz crystal resonator

Area of Science:

• Materials Science
• Physical Chemistry
• Surface Science

Background:

• Quartz crystal resonators are sensitive to mass loading.
• Polyelectrolyte multilayers exhibit complex interactions with liquids.
• Apparent negative areal mass densities suggest phenomena beyond simple mass addition.

Purpose of the Study:

• To explain the observed negative areal mass densities in polyelectrolyte multilayer systems.
• To investigate the role of interfacial slippage in resonator measurements.
• To compare different physical models of interfacial slippage.

Main Methods:

• Utilized quartz crystal resonator measurements in contact with perfluorocarbon liquids.
• Modeled the interfacial slippage zone as a distinct layer with physical parameters.
• Analyzed three slippage models: de Gennes (gas cavity), water layer, and true slipping (velocity discontinuity).
• Calculated slippage admittances, slippage lengths, and corrected areal mass densities.

Main Results:

• Interfacial slippage was identified as the cause of apparent negative areal mass densities.
• All three models provided calculated parameters, but with varying degrees of fit.
• The de Gennes model showed slightly less variation in calculated parameters, suggesting greater credibility.

Conclusions:

• Interfacial slippage is a critical factor in interpreting quartz crystal resonator data for multilayers in liquids.
• The de Gennes model offers a plausible explanation for the observed phenomenon.
• Further experimental validation is needed to definitively favor one slippage model.