3D Printable Poly(N-isopropylacrylamide) Microgel Suspensions with Temperature-Dependent Rheological Responses
Zhecun Guan1, Sai Krishna Katla2, Vidumin Dahanayake2
1Department of NanoEngineering, University of California San Diego, La Jolla, California 92093, United States.
ACS Applied Polymer Materials
|December 19, 2024
Summary
Stimuli-responsive poly(N-isopropylacrylamide) (PNIPAm) microgels show tunable liquid-to-paste transitions. Their temperature-dependent rheology is sensitive to heating/cooling rates, impacting applications in drug delivery and tissue engineering.
Area of Science:
- Materials Science
- Polymer Science
- Soft Matter Physics
Background:
- Microgel suspensions exhibit tunable phase transitions from liquid-like to paste-like states.
- Stimuli-responsive microgels offer faster volume changes than bulk materials while retaining structural integrity.
Purpose of the Study:
- To characterize the temperature-responsive rheological behavior of poly(N-isopropylacrylamide) (PNIPAm) microgel suspensions.
- To investigate the influence of temperature ramp rate and microgel mass fraction on rheological properties.
Main Methods:
- Preparation of concentrated and diluted PNIPAm microgel suspensions in water at various packing fractions.
- Rheological characterization under controlled temperature changes (ramping).
- Investigation of microgel size changes and interactions during the volume phase transition (VPT).
Main Results:
- PNIPAm microgels undergo a volume phase transition (VPT) where polymer chains collapse, leading to microgel shrinkage.
- VPT alters intermicrogel and microgel-solvent interactions, forming clusters that affect suspension shear moduli.
- Rheological responses are dependent on the heating and cooling ramp rates.
- Microgel mass fraction significantly influences the relative viscosity of dilute suspensions.
Conclusions:
- The study elucidates the heating and cooling rate-dependent temperature responsiveness of PNIPAm microgel suspensions.
- Findings provide pathways to regulate rheological characteristics for advanced microgel-based platforms.
- Potential applications include drug delivery, tissue engineering, and diagnostic tools.
