How Cross-Linking Influences the Electrochemical Properties for Brush-Functionalized Electrodes

Area of Science:

• Electrochemistry
• Materials Science
• Polymer Science

Background:

• Hydrogel brushes offer electrochemical stability due to their cross-linked polymer network.
• Their electrochemical properties remain largely unexplored.
• Poly(3-sulfopropyl methacrylate) (PSPMA) hydrogel brushes are negatively charged and suitable for electrochemical applications.

Purpose of the Study:

• Investigate the impact of cross-linker content on the electrochemical behavior of PSPMA hydrogel brushes.
• Understand the role of layer resistance in a poor solvent and charge transfer in a good solvent.
• Determine how cross-linking affects ion diffusion and charge transfer properties.

Main Methods:

• Electrochemical impedance spectroscopy (EIS) was employed.
• Studies were conducted in a poor solvent (0.1 M KOH) and a good solvent (0.1 M KCl).
• The effect of varying cross-linker content on hydrogel brush properties was analyzed.

Main Results:

• In 0.1 M KOH, the polymer layer's resistance to ion diffusion is dependent on cross-linker content, with an optimal content minimizing resistance.
• This optimum is linked to the balance between flexible and rigid polymer phases.
• In 0.1 M KCl, solvated brush thickness dictates charge transfer resistance; higher cross-linking reduces swelling and lowers resistance.

Conclusions:

• Cross-linker content is a tunable parameter for managing layer resistance and charge transfer in hydrogel brushes.
• Findings are applicable to optimizing materials for corrosion protection, electrochemical sensing, and ion gating.
• Understanding cross-linker effects enables tailored electrochemical performance of hydrogel brushes.