Interfacial Tension of Phase-Separated Polydisperse Mixed Polymer Solutions

Area of Science:

• Polymer science
• Physical chemistry
• Colloid and surface science

Background:

• Aqueous two-phase systems (ATPS) offer oil-free alternatives for emulsion formulation.
• High polymer polydispersity complicates theoretical interpretation of ATPS measurements.
• Understanding interfacial behavior is crucial for optimizing ATPS applications.

Purpose of the Study:

• To investigate the effect of small polymer addition on phase behavior and interfacial tension in ATPS.
• To elucidate the role of polymer size and composition in interfacial phenomena.
• To provide a theoretical framework for describing polydispersity effects in ATPS.

Main Methods:

• Experimental determination of phase diagrams and interfacial tensions for dextran-gelatin systems.
• Theoretical calculations using Scheutjens-Fleer self-consistent field lattice theory.
• Analysis of partial contributions of components to interfacial tension.

Main Results:

• Small dextran molecules (20 kDa) were found to decrease interfacial tension in ATPS containing large dextran (70 kDa) and gelatin (100 kDa).
• At equal tie-line length, smaller polymers reduced interfacial tension compared to systems without them.
• Analysis revealed that small polymers displace excess water at the interface.

Conclusions:

• The addition of small polymers effectively modulates interfacial tension in ATPS.
• The Gibbs adsorption equation provides a useful model for understanding polydispersity effects on interfacial tension.
• Findings contribute to the rational design of ATPS for various applications, including food and biotechnology.