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

TL;DR

This study shows that neutral polymer brushes can have long-range electrostatic interactions with contaminants, challenging previous assumptions about their antifouling properties.

Contribution

The paper introduces a novel method using TIRM to directly measure overlooked long-range interactions near antifouling polymer brushes.

Findings

Seemingly neutral polymers exhibit significant electrostatic interactions with nearby contaminants.

Long-range interactions are influenced by ionic strength and polymer conformation.

Current assumptions about charge absence on antifouling surfaces are challenged.

Abstract

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.

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