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Swelling Behavior of PNIPAM Toroidal Hydrogels

Ya-Wen Chang

Temperature responsive PNIPAM hydrogel undergo swelling/deswelling transition at its volume phase transition temperature, above which the polymer becomes hydrophobic and the hydrogel enters a completely deswollen state in equillibrium. Spherical hydrogel deswells by changing its diameter, i.e., reducing its total volume, to satisfy the osmotic pressure balance between the polymer network and the surrounding solvent. Using a toroidal-shaped hydrogel, where the reduction in volume could correspond to the change in both tube radius and radius of the inner circle, we study how these two quantities are coupled or decoupled in the shrinking process. Additionally, we control the rate at which the hydrogel experience temparature change across the transition temperature. For bulk hydrogel, rapid heating result in the formation of a thin, impermeable shell of collapsed polymer at the surface while the interior is still in the swollen state, resulting in morphology destabilization in the case of a torus. We're currently developing theoretical mechansim to describe the shape change. We have also started looking at different modes of buckling in relation to the aspect ratio.

Video: Deswelling of toroidal hydrogel with (left) slow and (right) fast temperature ramp.

Biofilm project: Alexandros Fragkopoulos, Harold Kim (Gatech), Thomas Angelini (University of Florida)
Tissue cell project: Ricardo Cruz (Garcia group), Andres Garcia (Gatech)
Hydrogel project: Michael Dimitriyev (Goldbart group), Anton Souslov (Goldbart group), Paul Goldbart (Gatech)

Soft Condensed Matter Laboratory, School of Physics, Georgia Institute of Technology
770 State Street NW, Atlanta, GA, 30332-0430, USA
Phone: 404-385-3667 Fax: 404-894-9958
alberto.fernandez [at] physics.gatech.edu