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

Current research on the antifouling mechanisms of "electrically neutral" polymer brushes predominantly emphasizes thermodynamically unfavorable short-range interactions. However, our study reveals the critical importance of long-range interactions. By utilizing zwitterionic poly(carboxybetaine methacrylate) (PCBMA) and nonionic poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) brushes as model systems, we employed total internal reflection microscopy (TIRM) to directly measure interactions with contaminants. Surprisingly, even seemingly neutral polymers exhibit significant electrostatic interactions with nearby contaminants─a fact that has been largely overlooked in this field. Our findings challenge the prevailing assumption of charge absence on surfaces grafted with antifouling polymer brushes and investigate how external stimuli (such as ionic strength and polymer conformation) affect these long-range interactions. In conclusion, this study presents a novel approach to exploring long-range interactions near polymer-grafted surfaces, offering valuable insights for the development of antifouling materials and biomedical applications in the future.