CO2 responsive colloids are of interest for the delivery of active molecules in both pharmaceutical applications and for gas treatment technologies, among others. Primary and secondary organic amines react with CO2 gas in aqueous solution to form ionic carbamates in an exothermic "CO2 sequestration" reaction. Several amines important in this context are 2-aminoethanol, 2,2′-iminodiethanol, and piperazine. We have used small-angle X-ray scattering at a high intensity synchrotron source to demonstrate that triblock copolymer micelles containing carbamate-forming amines change shape upon exposure to CO2. Modeling of the scattering data is used to elucidate the effects of exposure on micelle size and morphology. Electron density distribution within the micelles, derived from the SAXS data, established that the amines interact with the polymer micelles. The products of CO2 exposure, namely, carbamate, bicarbonate anions, and protons, modify the packing of the polymer chains, and occupy the volume within the polymer aggregates. Our findings contribute to the detailed understanding and optimization of liquid based CO2-responsive systems.
Salentinig, S., Jackson, P., & Hawley, A. (2015). Amine-functionalized CO2 responsive triblock copolymer micelles-a small-angle X-ray scattering study. Macromolecules, 48(7), 2283 - 2289. https://doi.org/10.1021/ma502584p