Multicomponent diffusion of interacting, nonionic micelles with hydrophobic solutes.

Area of Science:

• Physical Chemistry
• Colloid Science
• Transport Phenomena

Background:

• Understanding diffusion in complex fluids like micellar solutions is crucial for various applications.
• Crowded solutions exhibit non-ideal behavior due to inter-particle interactions and structural organization.
• Ternary diffusion coefficients describe mass transport in multi-component systems.

Purpose of the Study:

• To experimentally measure ternary diffusion coefficient matrices [D] in crowded aqueous solutions of decaethylene glycol monododecyl ether (C12E10) with decane or limonene.
• To evaluate a simplified theoretical model based on Batchelor's theory for predicting these diffusion coefficients.
• To assess the model's accuracy in concentrated mixtures.

Main Methods:

• Taylor dispersion method for measuring ternary diffusion coefficient matrices.
• Preparation of crowded aqueous solutions of C12E10 with decane or limonene solutes.
• Application of a simplified theoretical model derived from Batchelor's theory.

Main Results:

• Ternary diffusion coefficient matrices [D] were found to be non-diagonal and concentration-dependent.
• The simplified theoretical model accurately predicted [D] for concentrated mixtures (up to φ≈ 0.47) without adjustable parameters.
• Predicted eigenvalues D- and D+ showed reasonable agreement with experimental data for self and gradient diffusion coefficients.

Conclusions:

• A simplified theoretical model effectively predicts ternary diffusion coefficients in concentrated micellar solutions.
• The model's success highlights its applicability beyond dilute systems.
• Experimental and theoretical findings advance the understanding of transport phenomena in complex fluids.