Investigating Adsorbing Viscoelastic Fluids Using the Quartz Crystal Microbalance

Area of Science:

• Materials Science
• Physical Chemistry
• Chemical Engineering

Background:

• Quartz crystal microbalance (QCM) is underutilized for studying adsorbing viscoelastic fluids.
• Viscoelastic fluids are common but challenging to analyze due to opacity and high viscosity.
• QCM offers a non-scattering, non-reflective method suitable for complex fluid analysis.

Purpose of the Study:

• To investigate the application of QCM for analyzing viscoelastic fluids and surface adsorption.
• To compare QCM responses for Newtonian and viscoelastic fluids.
• To develop and validate a modified QCM model for viscoelastic fluid characterization.

Main Methods:

• Comparison of QCM responses for Newtonian (sucrose) and viscoelastic (sodium polystyrene sulfonate - NaPSS) fluids.
• Application of a viscoelastic model to determine high-frequency viscosity and shear modulus.
• Modification of the Kanazawa and Gordon (KG) model using the QCM shear wave decay length ratio (X).
• Investigation of NaPSS adsorption on silica and alumina substrates.

Main Results:

• QCM responses for Newtonian fluids aligned with the KG model.
• Viscoelastic NaPSS solutions showed responses below the KG model predictions.
• Significant increase in shear modulus (several orders of magnitude) observed for NaPSS at QCM frequencies.
• Modified KG model successfully matched experimental QCM frequency and dissipation values for NaPSS.
• NaPSS adsorption on alumina was quantified using a Langmuir isotherm, even with small frequency shifts.

Conclusions:

• QCM is a viable technique for characterizing viscoelastic fluids and their adsorption behavior.
• A modified KG model effectively accounts for viscoelasticity in QCM analysis.
• QCM can determine bulk fluid properties and surface adsorption simultaneously.
• The study demonstrates QCM's potential for analyzing complex fluid systems relevant in various industrial applications.