# Ammonium-Containing Methacrylic Polymer Brushes with Adjustable Hydrophilicity: Synthesis and Properties in Aqueous Solutions

## TL;DR

Scientists created a new type of polymer brush that can change its water-loving or water-repelling properties, making it useful for drug delivery.

## Contribution

The study introduces thermoresponsive cationic molecular brushes with tunable hydrophilicity and antibacterial potential.

## Key findings

- The polymers exhibit tunable lower critical solution temperature (LCST) behavior between 17–68 °C.
- Brush micelles effectively solubilize hydrophobic compounds in water.
- The polymers significantly reduce water–oil interfacial tension and have low critical micelle concentrations.

## Abstract

Reversible addition–fragmentation chain-transfer (RAFT) polymerization was used to synthesize novel thermoresponsive cationic molecular brushes with high yields—namely of copolymers of methoxyoligo(ethylene glycol) methacrylate, alkoxyoligo(ethylene glycol) methacrylate, and N-methacryloylaminopropyl-N,N-dimethyl-N-propylammonium bromide. Controlled polymerization yielded polymers with a molecular weight dispersity of ≤1.3 and conversions exceeding 80%. The influence of the cationic molecular brushes’ composition on their solubility in water and organic solvents, interfacial tension at the water–oil interface, and aggregation behavior in aqueous solutions was investigated. For the first time, we report the design of thermoresponsive cationic molecular brushes combining an antibacterial potential and tunable hydrophilic–hydrophobic properties, enabling highly precise control over their LCST behavior (17–68 °C) through composition tuning. The solubilization capacity of the hydrophobic compounds of brush micelles in water increased with the hydrophobic comonomer content. These polymers exhibited interfacial activity, significantly reducing the water–oil interfacial tension, with critical micelle concentrations (CMCs) of 3–10 mg/L. It was shown that the amphiphilic properties of the copolymers in aqueous solutions can be easily tuned in a desired direction by varying the content of the comonomer units. The obtained data indicate the potential of the polymers as micellar nanocarriers for controlled drug delivery.