Structural changes in block copolymer micelles induced by cosolvent mixtures.

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Polymeric micelles are self-assembled nanostructures with potential applications in drug delivery.
• Controlling micelle structure, such as size and interfacial properties, is key to optimizing their performance.
• Poly(1,2-butadiene-b-ethylene oxide) [PB-PEO] is a block copolymer used to form starlike micelles in aqueous solutions.

Purpose of the Study:

• To investigate the effect of tetrahydrofuran (THF) addition on the structural properties of PB-PEO micelles.
• To understand how changes in interfacial tension influence micelle morphology and chain accessibility.
• To explore the potential of THF as a tool for tuning micelle characteristics for delivery applications.

Main Methods:

• Small angle neutron scattering (SANS) with contrast variation was employed to study micelle structure.
• Scattering data were analyzed using form factors accounting for radial density distribution and Gaussian coils.
• Micelle size, core-corona interfacial tension, and chain accessibility were quantified.

Main Results:

• THF addition decreased micelle size and core-corona interfacial tension while maintaining a starlike structure.
• Low THF concentrations (high interfacial tension) required a radial density distribution model.
• High THF concentrations (low interfacial tension) necessitated a combination of micelle and Gaussian coil form factors due to free chains.
• Reduced interfacial tension led to a broader core-corona interface and increased poly(1,2-butadiene) [PB] chain solvent accessibility.
• Micelle cores swelled with increasing THF content, challenging previous assumptions about solvent content.

Conclusions:

• Tetrahydrofuran addition effectively modulates the structure of PB-PEO micelles, reducing size and interfacial tension.
• The observed changes in interfacial tension and core swelling provide insights into micelle behavior in cosolvent mixtures.
• Tuning micelle size, corona thickness, and PB chain accessibility offers a pathway for developing advanced drug delivery vehicles.