Microstructure-driven self-assembly and rheological properties of multi-responsive soft microgel suspensions

Area of Science:

• Polymer Science
• Materials Science
• Rheology

Background:

• Microgel properties like deformation and swelling are dictated by crosslinking distribution.
• Tailoring microgel microstructure can yield suspensions with distinct rheological behaviors.

Purpose of the Study:

• To investigate how varying crosslinker types (MBA and OEGDA) and amounts affect microgel microstructure.
• To correlate microgel microstructure with the rheological properties of concentrated suspensions.

Main Methods:

• Synthesis of multi-responsive microgels using MBA and OEGDA crosslinkers.
• Rheological analysis via zero-shear viscosity and creep measurements.
• Microstructure characterization using 1H nuclear magnetic resonance (NMR) transverse relaxation (T2).

Main Results:

• OEGDA-crosslinked microgels exhibited higher viscosity divergence than MBA ones, indicating a looser shell.
• Viscosity curves scaled with effective volume fraction, aligning with hard-sphere models.
• MBA microgels displayed significantly higher yield stress and a less crosslinked shell, confirmed by NMR.

Conclusions:

• Microgel shell crosslinking density is a critical factor influencing rheological properties.
• The study provides a method to tune microgel suspension flow behavior by controlling crosslinking.
• NMR and rheology confirm that MBA crosslinking leads to looser microgel shells compared to OEGDA.