Ionic strength dependent forces between end-grafted Poly(sulfobetaine) films and mica

Area of Science:

• Surface Science
• Polymer Chemistry
• Colloid Science

Background:

• Zwitterionic polymer coatings are known for ultra-low fouling and steric stabilization.
• Their effectiveness is linked to molecular surface properties, especially in high salt conditions.

Purpose of the Study:

• To quantify molecular forces of end-grafted poly(sulfobetaine) methacrylate films using Surface Force Apparatus.
• To investigate the influence of chain grafting density and ionic strength on these forces.

Main Methods:

• Utilized Surface Force Apparatus (SFA) to measure forces between poly(sulfobetaine) films and mica.
• Applied polymer physics models (Milner-Witten-Cates, Dolan and Edwards) to analyze force data.

Main Results:

• Poly(sulfobetaine) films behaved as polymers in a good solvent across tested ionic strengths.
• Analysis revealed changes in poly(sulfobetaine) swelling and excluded volume with varying ionic strength.
• Force measurements provided insights into the interplay of polymer coverage and salt concentration.

Conclusions:

• Polymer coverage and salt concentration cooperatively regulate repulsive steric barriers in poly(sulfobetaine) coatings.
• Findings inform the design of poly(sulfobetaine) for colloidal stabilization and nonfouling applications.