Domain Alignment and Solvent Swelling Impact Ion Transport in a Multiblock Copolymer Ionomer

Area of Science:

• Materials Science
• Polymer Chemistry
• Electrochemistry

Background:

• Ionic conductivity in polymers is crucial for applications like batteries and fuel cells.
• Nanostructured ionomers offer potential for improved ion transport.
• Solvent swelling and nanostructure alignment are key strategies to enhance ionic conductivity.

Purpose of the Study:

• To investigate the combined effects of solvent swelling and nanostructure alignment on the ionic conductivity of a precise amphiphilic multiblock copolymer ionomer.
• To understand the role of solvent interactions with polymer morphology on ion transport pathways.

Main Methods:

• Thin films of an amphiphilic multiblock copolymer ionomer were prepared.
• Samples were characterized using grazing incidence X-ray scattering and broadband dielectric spectroscopy under saturated solvent vapor.
• Ionic conductivity was measured in-plane using interdigitated electrodes.

Main Results:

• Swelling with polar solvents (propylene carbonate, γ-butyrolactone, dimethyl carbonate, diglyme) and alignment of ionic assemblies parallel to the substrate significantly increased in-plane ionic conductivity.
• An isotropic bulk sample showed higher conductivity than an aligned thin film when swollen with propylene carbonate, suggesting preferential solvent uptake at defects.

Conclusions:

• Both nanostructure alignment and solvent swelling are effective in enhancing ionic conductivity in ionomers.
• Preferential swelling of grain boundaries and defects in bulk samples can create efficient ion transport pathways.
• Further improvements in ionic conductivity can be achieved by optimizing solvent interactions with nanostructured ionomers.