Surfactants are employed in materials and biological science to generate self-assembly structures to stabilize interfaces, affect solubilisation, morphology, biological and physicochemical properties. Conventionally, surfactant properties are manipulated by varying pH, temperature, and ionic strength, often leading to irreversible changes in system composition and phase stability. However, a more sophisticated approach is to use external stimuli to activate changes in molecular architecture, manifesting itself in changes in the overall system. CO2-switchable surfactants based on the reaction of CO2 with built in functional groups such as amines and amidines to form amidinium bicarbonates, zwitterionic adducts or ammonium carbamates have recently received much interest as CO2 exhibits good biocompatibility and is non-toxic and abundant. However, on the molecular level all the mechanisms rely on switching “on” and “off” of the surfactant. Here, we show a new class of CO2-reactive ionic liquid surfactants where the counterion is the responsive species, allowing for fine tunability of surfactant properties. We report how alteration in the surfactant architecture and electrostatics after reaction with CO2 feeds through to significant changes in micellar structure as well as surface tension in a way not seen by any other surfactants. In turn, we demonstrate how this can be put into effect in various colloidal systems ranging from microemulsions to polymers suitable for applications in enhanced oil recovery, catalysis, CO2-capture and novel ionic liquid separations. In particular relevance to gene therapy and targeted drug delivery, we demonstrate surfactant binding to DNA (and other biomolecules) and reversible compaction on bubbling with CO2 and N2.

CO2-reactive surfactant ionic liquids for reversible control of colloidal morphology and DNA compaction

249th National Meeting (2015)

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CO2-reactive surfactant ionic liquids for reversible control of colloidal morphology and DNA compaction<br />

CO₂-reactive surfactant ionic liquids for reversible control of colloidal morphology and DNA compaction<br />