A microgel-Pickering emulsion route to colloidal molecules with temperature-tunable interaction sites

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Polymer Science

Background:

• Polymer microgels are versatile building blocks for advanced materials.
• Controlling the assembly and interactions of microgels is crucial for designing functional colloidal systems.
• Temperature-responsive polymers offer dynamic control over material properties.

Purpose of the Study:

• To develop a simple Pickering emulsion route for assembling temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) microgel particles into colloidal molecules.
• To create microgel-based colloidal molecules with tunable, temperature-dependent interaction sites.
• To extend the method for creating patchy colloidal molecules using microgels with different volume phase transition temperatures (VPTTs).

Main Methods:

• Utilizing a Pickering emulsion strategy for microgel assembly around oil droplets.
• Employing in situ synthesis of monodisperse polydimethylsiloxane (PDMS) emulsion droplets.
• Using a dialysis step to control droplet size and limit further growth.
• Incorporating temperature-responsive PNIPAM and poly(N-isopropylmethacrylamide) (PNIPMAM) microgels.

Main Results:

• Successfully assembled PNIPAM microgels into colloidal molecules with discrete interaction sites on PDMS emulsion droplets.
• Achieved narrowly size-distributed colloidal molecules with well-defined microgel arrangements.
• Demonstrated that the temperature-responsiveness of PNIPAM allows tuning of interactions from repulsive to attractive by crossing the VPTT.
• Extended the approach to create patchy colloidal molecules using a mixture of PNIPAM and PNIPMAM microgels with distinct VPTTs.

Conclusions:

• The Pickering emulsion route provides a facile method for constructing temperature-responsive microgel colloidal molecules.
• The developed colloidal molecules offer tunable directional interactions, enabling precise control over assembly.
• The ability to create patchy colloidal molecules with differential VPTTs opens avenues for complex, stimuli-responsive material design.