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Updated: May 3, 2026

Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions
Published on: April 19, 2018
Dynamics of a thermo-responsive microgel colloid near to the glass transition
Xiaojun Di1, Xiaoguang Peng1, Gregory B McKenna1
1Department of Chemical Engineering, Texas Tech University, Lubbock, Texas 79409, USA.
Abstract:
In a previous study, we used diffusing wave spectroscopy (DWS) to investigate the aging signatures of a thermo-sensitive colloidal glass and compared them with those of molecular glasses from the perspective of the Kovacs temperature-jump, volume recovery experiments [X. Di, K. Z. Win, G. B. McKenna, T. Narita, F. Lequeux, S. R. Pullela, and Z. Cheng, Phys. Rev. Lett. 106, 095701 (2011)]. In order to further look into the glassy behavior of colloidal systems, we have synthesized a new core/shell particle with lower temperature sensitivity and studied the aging signatures of concentrated systems, again following Kovacs' protocol. Similar signatures of aging to those observed previously were seen in this new system. Moreover, a systematic study of the temperature dependence of the dynamics of the new system for different weight concentrations was performed and the dynamic fragility index m was determined. We have also explored the use of the properties determined from the DWS measurements to obtain macroscopic rheological parameters - storage modulus G(')(ω) and loss modulus G(″)(ω) - using a generalized Stokes-Einstein approach. The micro-rheological and macro-rheological values are in reasonable agreement.
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