The evolution of bicontinuous polymeric nanospheres in aqueous solution

Area of Science:

• Polymer Science and Engineering
• Materials Science
• Nanotechnology

Background:

• Complex polymeric nanospheres are valuable for encapsulation and templating.
• Understanding their formation in solution is key to controlling final structures.
• Block copolymers with temperature-responsive properties offer tunable self-assembly.

Purpose of the Study:

• To elucidate the formation mechanism of bicontinuous polymeric nanospheres (BPNs).
• To investigate the role of temperature-responsive block copolymers in aqueous solution.
• To correlate solution conditions with the evolution of nanosphere morphology.

Main Methods:

• Utilized cryo-transmission electron microscopy (cryoTEM) for structural visualization.
• Employed small-angle X-ray scattering (SAXS) to analyze nanoscale structures.
• Studied copolymer behavior in tetrahydrofuran (THF)-water mixtures and during dialysis.

Main Results:

• Observed a transition from vesicles to irregular aggregates with increasing water content.
• Identified a cononsolvency regime for the copolymer in THF-water mixtures (22-36%).
• Demonstrated that BPNs form upon cooling aqueous dispersions from 35 °C to 5 °C, indicating a reversible temperature-induced morphological transition.

Conclusions:

• The formation of bicontinuous polymeric nanospheres is a reversible, temperature-driven process.
• Precise control over temperature is crucial for achieving the desired BPN morphology.
• This study provides a mechanism for designing complex nanostructures from responsive polymers.