Structure Regulation of Block Copolymer Assemblies in Emulsion Droplets by Adding a Selective Solvent

Area of Science:

• Polymer Science
• Materials Science
• Nanotechnology

Background:

• Block copolymers (BCPs) self-assemble into nanostructures like particles or micelles.
• Traditional methods include 3D confined self-assembly (3D-CSA) for particles and solution self-assembly for micelles.

Purpose of the Study:

• To develop a facile strategy to control the assembled structures of poly(styrene-block-4-vinylpyridine) (PS-b-P4VP).
• To transition BCP assemblies from nanostructured particles to micelles.

Main Methods:

• Emulsion-solvent diffusion-induced self-assembly via dialysis.
• Addition of a P4VP-selective solvent (ethanol) to the dialysate to tune interfacial properties.
• Investigating structural transitions based on ethanol concentration.

Main Results:

• Ethanol addition alters interfacial selectivity and packing parameters, causing structural transitions in PS-b-P4VP nanostructures.
• High ethanol concentrations (≥50 vol%) induce interfacial instability, leading to micelle formation.
• Decreased interfacial tension due to increased ethanol and P4VP solubility drives micelle formation.

Conclusions:

• The developed strategy effectively bridges 3D-CSA and solution self-assembly.
• This method provides a promising route for engineering polymer assembly morphologies and nanostructures.
• The approach offers precise control over BCP assembly by tuning interfacial behavior.