Dynamically Cross-Linked Self-Assembled Thermoresponsive Microgels with Homogeneous Internal Structures

Area of Science:

• Polymer Science
• Materials Science
• Soft Matter Physics

Background:

• Poly(N-isopropylacrylamide) (PNIPAM) microgels are temperature-responsive materials with tunable properties.
• Conventional microgel synthesis often leads to heterogeneous internal structures (dense core, diffuse shell).
• Understanding microgel internal morphology is crucial for optimizing their performance in various applications.

Purpose of the Study:

• To investigate the internal morphology of PNIPAM microgels synthesized via aqueous self-assembly.
• To compare the structure of these self-assembled microgels with conventionally synthesized ones.
• To explore the implications of the internal structure on potential applications.

Main Methods:

• Aqueous self-assembly of hydrazide and aldehyde-functionalized PNIPAM oligomers.
• Surface force measurements.
• Small angle neutron scattering (SANS) and ultrasmall angle neutron scattering (USANS).

Main Results:

• Demonstrated a homogeneously cross-linked internal structure in the self-assembled PNIPAM microgels.
• This homogeneous structure contrasts with the expected core-shell morphology and conventional microgels.
• The structure is attributed to dynamic hydrazone chemistry and conditions promoting polymer interdiffusion.

Conclusions:

• The self-assembly process yields PNIPAM microgels with a unique homogeneous internal structure.
• This uniform cross-linking is distinct from conventional microgels and offers potential advantages.
• The findings suggest improved drug release consistency, enhanced optical properties, and broader application potential for these microgels.