Solvent effect on the aggregation behavior of rod-coil diblock copolymers

Area of Science:

• Polymer Science
• Materials Science
• Supramolecular Chemistry

Background:

• Rod-coil diblock copolymers self-assemble into diverse nanostructures.
• Poly(ethylene oxide) (PEO) and poly{(+)-2,5-bis[4'-((S)-2-methylbutoxy)phenyl]styrene} (PMBPS) are key components in block copolymer research.
• Understanding solvent effects on copolymer aggregation is crucial for materials design.

Purpose of the Study:

• Investigate the water-induced aggregation of PEO104-b-PMBPS53.
• Determine the influence of common (THF) and selective (dioxane) solvents on aggregate characteristics.
• Elucidate the packing and orientation of PMBPS blocks within aggregates.

Main Methods:

• Solution preparation using tetrahydrofuran (THF) and dioxane.
• Controlled addition of water to induce copolymer aggregation.
• Dynamic light scattering (DLS) for aggregate size and distribution analysis.
• 2D wide-angle X-ray diffraction (2D-WAXD) and polarized optical microscopy (POM) for structural characterization.

Main Results:

• Copolymer remained as single chains in pure THF or dioxane.
• Aggregation initiated at approximately 6 wt% water, dominated by the PMBPS block.
• Dioxane/water yielded uniform spheres (~20 nm), while THF/water produced bimodal distributions (~3 nm and ~300 nm).
• 2D-WAXD and POM revealed parallel PMBPS packing in dioxane/water and anisotropic, disklike structures in THF/water.

Conclusions:

• The solvent medium critically dictates the morphology and structure of PEO-b-PMBPS aggregates.
• PMBPS block orientation varies with solvent, influencing aggregate formation.
• These findings offer insights into controlling self-assembly for advanced materials applications.