Near-Surface Concentration Profile of Sheared Semidilute Polymer Solutions.

Area of Science:

• Polymer physics
• Surface science
• Materials science

Background:

• Controlling polymer solution structure at solid interfaces is vital for industrial processes, affecting flow and slip.
• Experimental investigation of solid/liquid interfaces at the nanoscale is challenging due to limited techniques.

Purpose of the Study:

• To experimentally probe the polymer solution interface structure at the nanoscale.
• To investigate the behavior of polymer chains near a solid surface under both static and flow conditions.

Main Methods:

• Utilized neutron reflectivity to study a semidilute polystyrene solution interface with a smooth sapphire surface.
• Developed and optimized a specialized setup for in-situ flow measurements under shear.

Main Results:

• At rest, polymer chains were globally depleted from the solid surface, with some chains adsorbing onto the wall.
• Under shear flow, the depletion layer was experimentally confirmed to remain stable, contrary to vague literature confirmations.

Conclusions:

• The study provides experimental evidence of polymer chain adsorption and depletion layer stability at solid/liquid interfaces.
• Findings offer critical insights into polymer solution behavior under flow, relevant for industrial applications.