Direct Measurements of Overlooked Long-Range Interactions near Zwitterionic and Nonionic Polymer Brushes

Area of Science:

• Materials Science
• Surface Chemistry
• Biomedical Engineering

Background:

• Current antifouling research on polymer brushes primarily focuses on short-range repulsive forces.
• The role of long-range interactions, particularly electrostatic forces, has been largely overlooked for seemingly neutral polymer brushes.

Purpose of the Study:

• To investigate the significance of long-range interactions in the antifouling mechanisms of polymer brushes.
• To challenge the assumption of charge neutrality on surfaces modified with antifouling polymer brushes.
• To explore the influence of external stimuli on these interactions.

Main Methods:

• Utilized zwitterionic poly(carboxybetaine methacrylate) (PCBMA) and nonionic poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) brushes as model systems.
• Employed total internal reflection microscopy (TIRM) for direct measurement of interactions between polymer brushes and contaminants.
• Investigated the effects of ionic strength and polymer conformation on interaction forces.

Main Results:

• Demonstrated that even ostensibly neutral polymer brushes exhibit substantial long-range electrostatic interactions with contaminants.
• Revealed that these electrostatic interactions are critical and have been previously underestimated in antifouling strategies.
• Showcased the tunability of these long-range interactions by altering environmental conditions.

Conclusions:

• Challenges the prevailing understanding of antifouling mechanisms, highlighting the importance of long-range electrostatic forces.
• Provides a novel methodology for studying interactions at polymer-grafted surfaces.
• Offers critical insights for designing next-generation antifouling materials for diverse applications, including biomedical devices.