Ion channels in sulfonated copolymer-grafted nanoparticles in ionic liquids

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Ionic liquids offer unique solvent properties for polymer electrolytes.
• Polymer-grafted nanoparticles can modify electrolyte behavior.
• Understanding electrolyte-polymer interactions is crucial for advanced materials.

Purpose of the Study:

• To investigate the effect of ionic liquids on the ionic conductivity of polymer-grafted nanoparticles.
• To explore the relationship between nanoparticle concentration and conductivity in different solvent systems.
• To elucidate the mechanisms governing ionic transport in these complex electrolytes.

Main Methods:

• Synthesis of poly(methyl methacrylate)-b-poly(styrene sulfonate) (PMMA-b-PSS) copolymer-grafted Fe₃O₄ nanoparticles with varying sulfonation levels.
• Measurement of ionic conductivities in acetonitrile and mixtures of 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIm-TFSI) and acetonitrile at different particle concentrations.
• Analysis of conductivity dependence on particle loading and solvent composition.

Main Results:

• In acetonitrile, particle aggregation enhanced conductivity due to connected sulfonic domains.
• Ionic conductivity correlated with effective hopping transfer within ionic channels.
• In HMIm-TFSI/acetonitrile mixtures, conductivity decreased or remained constant with increasing particle concentration.
• This decrease was attributed to ion coupling between the ionic liquid and copolymer domains.

Conclusions:

• The solvent environment significantly impacts the ionic conductivity of polymer-grafted nanoparticles.
• Ion coupling between ionic liquids and polymer chains can hinder ion transport.
• These findings provide insights into designing advanced polymer electrolytes for energy storage applications.