Self-Consistent Field Analysis of Segregative Aqueous Dextran─Poly(ethylene glycol) Solutions: (3) Polymer-Induced...

Area of Science:

• Colloid and Surface Science
• Soft Matter Physics
• Polymer Science

Background:

• Aqueous two-phase systems (ATPS) are crucial in bioseparation and biomaterials.
• Colloidal particles can induce gelation in ATPS by forming capillary bridges.
• Understanding particle interactions is key to controlling ATPS properties.

Purpose of the Study:

• Investigate gel formation in a silica-particle-stabilized dextran-PEG ATPS.
• Analyze interparticle forces, including polymer-induced and capillary contributions.
• Evaluate the validity of common simulation approximations.

Main Methods:

• Utilized Scheutjens-Fleer self-consistent field (SF-SCF) theory.
• Employed a molecularly detailed model for silica particles in ATPS.
• Calculated equilibrium force-distance relations, considering particle size, interfacial tension, Laplace pressure, and contact angle.

Main Results:

• Strong gelation observed above the percolation threshold.
• Interparticle interactions are dominated by polymer loop-to-bridge attractions.
• Capillary contributions are significant at larger distances but weaker than polymer forces.
• Three-gradient SF results suggest pairwise additivity may fail due to merging capillary bridges.

Conclusions:

• Polymer-induced forces are primary drivers of gelation in this ATPS.
• Capillary bridge merging can invalidate standard simulation assumptions.
• SF-SCF theory provides detailed insights into complex colloidal suspensions.