Paper Number
IR14 

Session
Interfacial Rheology, Surfactants, Foams, and Emulsions

Title
CO2-activated rheological transitions: Reversible transitions between wormlike micelles and vesicles

Presentation Date and Time
October 14, 2024 (Monday) 4:25

Track / Room
Track 6 / Room 501

Authors (Click on name to view author profile)

  1. Srivastava, Mahima (University of Maryland College Park, Chemical and Biomolecular Engineering)
  2. Philip, Ireen Maria (University of Maryland College Park, Department of Chemistry and Biochemistry)
  3. Raghavan, Srinivasa R. (University of Maryland)

Author and Affiliation Lines (in printed abstract book)
Mahima Srivastava1, Ireen Maria Philip2 and Srinivasa R. Raghavan3
1Chemical and Biomolecular Engineering, University of Maryland College Park, College Park, MD 20740; 2Department of Chemistry and Biochemistry, University of Maryland College Park, College Park, MD; 3University of Maryland, College Park, MD 20740

Speaker / Presenter 
Philip, Ireen Maria

Keywords
experimental methods; non-Newtonian fluids; surfactants

Text of Abstract
The self-assembly of surfactants in water can be tuned by several stimuli, including temperature, pH, and light. In particular, self-assembly into wormlike micelles (WLMs) has been shown to be sensitive to the above stimuli. WLMs are long, polymer-like chains that entangle into transient networks. Thus, when WLMs are formed, the solution becomes highly viscoelastic. Conversely, if WLMs are converted into spherical structures (micelles or vesicles), the viscoelasticity is lost, and the viscosity of the solution will drop to that of water. Here, we focus on modulating the self-assembly of WLMs using carbon dioxide (CO2). CO2 is of concern due to its role in the atmosphere as a greenhouse gas (thus impacting global warming and climate change). Approaches for CO2 sequestration often introduce gaseous CO2 into a solution containing an amine such as diethanolamine (DEA), but such amines are rather toxic molecules. We are interested in absorbing CO2 in a fluid that is completely safe and biocompatible. Moreover, could CO2 absorption transform the viscosity of the fluid? In this regard, we have devised a fluid containing an anionic fatty acid and a nontoxic amine-bearing molecule. Both the constituents of our fluid are biocompatible and in fact, they are found in the body. We will show that the viscosity of the fluid can be switched from low to high (or high to low) by contact with CO2. The low-viscosity state corresponds to vesicles (or spherical micelles) whereas the high-viscosity state corresponds to WLMs. By bubbling CO2 into a fluid of given composition, we can rapidly (within seconds) drive a transition from one type of self-assembly to another. We are interested in exploiting such rapid transitions, not only for CO2 sequestration but also for certain biomedical applications.