# Molecular Origins of Nonfrozen Water in Polyelectrolyte Brushes

## TL;DR

This study explores how polyelectrolyte brushes retain water at very low temperatures, offering insights for creating better anti-icing and lubricating coatings.

## Contribution

The paper provides direct measurements of nonfrozen water in polyelectrolyte brushes at subzero temperatures using infrared spectroscopy.

## Key findings

- PMETA brushes retain 25–35 vol. % water even at −60 °C.
- The study quantifies changes in polymer volume fraction with temperature.
- Spectroscopic analysis reveals substantial water confinement in charged polymer networks.

## Abstract

Polyelectrolyte brushes (PEBs) are promising coatings
for reducing
ice adhesion and regulating water freezing at interfaces, yet direct
measurements of nonfrozen water retention at subzero temperatures
remain scarce. Here, we investigate the freezing behavior of water
confined in poly­([2-(methacryloyloxy)­ethyl]­trimethylammonium) (PMETA)
brushes with chloride, iodide, and sulfate counterions using a custom-built
low-temperature attenuated total reflectance infrared spectroscopy
system. Furthermore, we quantify the fraction of water that was present
within the brush that does not freeze as well as the changes in polymer
volume fraction within the brush as a function of temperature. Spectroscopic
analysis of water vibrational modes reveals that PMETA brushes retain
25–35 vol. % water even at −60 °C, providing direct
evidence of substantial water confinement in charged polymer networks.
These findings advance the fundamental understanding of interfacial
water behavior in PEBs and suggest molecular design strategies for
engineering anti-icing and cryo-lubricating surface coatings.