Polymer-Iron Oxide Hybrid Films for Controlling Electrokinetic Properties

TL;DR

This paper presents a simple liquid-phase infiltration method to create polymer-iron oxide hybrid films with tunable electrokinetic properties, advancing control over interfacial charge for various technological applications.

Contribution

The study introduces a scalable, low-cost infiltration technique to modify polymer surfaces with metal oxides, enabling precise control of electrokinetic behavior.

Findings

Hybrid films exhibit electrokinetic properties similar to pure iron oxide.

Infiltration method preserves polymer integrity during oxide incorporation.

Surface charge and conductivity are tunable via oxide concentration.

Abstract

Electrokinetic phenomena at polymer-water interfaces are central to technologies for water purification, ion separations, and energy conversion, yet the ability to systematically control polymer surface charge and associated electrokinetic processes remains limited. Here, we demonstrate a simple liquid-phase infiltration (LPI) method to synthesize polymer-metal oxide hybrid films with controllable interfacial properties. Hydroxy-terminated poly(2-vinylpyridine) (P2VP-OH) brushes grafted to silicon substrates were infiltrated with iron nitrate from ethanolic solution, followed by low-temperature thermal treatment to convert the infiltrated precursor into iron oxide. Spectroscopic ellipsometry, X-ray photoelectron spectroscopy, and thermogravimetric analysis confirmed oxide incorporation and hybrid film formation without polymer degradation. Electrokinetic flow characterization reveals that the hybrid films acquire the electrokinetic properties of the infiltrated oxide, with concentration-dependent streaming potentials and surface conductivities closely matching those of pure iron oxide films. These results establish metal oxide infiltration as a scalable and low-cost strategy for controlling interfacial charge in polymer surfaces. The approach introduces new materials and design parameters for tailoring ion selectivity, transport, and energy conversion, with broad implications for the development of advanced membranes, electrokinetic harvesting devices, and polymer-supported oxide electrodes.