Sarah Gold

Tri‐Chain Hydrocarbon Surfactants as Designed Micellar Modifiers for Supercritical CO2

Getting their feet wet: Low-cost hydrocarbon surfactants act as fluid modifiers for supercritical carbon dioxide (scCO(2)). Increased terminal branching of the surfactant chains aids micelle formation (see middle picture: CO(2) green), and more chains allows water to be incorporated (right, blue).

Self-assembly in green solvents

Recent advances in design of surfactants and polymers for liquid and supercritical carbon dioxide, and partially fluorinated alkanes, are reviewed. The focus is on surfactant structure-performance relationships, development of non-fluorinated surfactants, and applications of CO2 continuous dispersions for nanoparticle and organic synthesis. Future prospects for these emerging technologies are discussed, including the need for economically viable and environmentally friendly stabilizers for CO2 dispersions.

Branched trichain sulfosuccinates as novel water in CO2 dispersants

A series of highly branched trichain sulfosuccinate surfactants have been synthesized and studied in condensed CO2 and aqueous environments. Aqueous critical micelle concentrations (CMCs) showed a general trend of increasing CMC with decreasing chain length, whereas increased branching appeared to increase solubility in CO2 and aid the dispersion of water. Near infrared spectra confirmed observed cloud with a large increase in solubility above the cloud pressures in this solvent.

Hydrocarbon Surfactants for CO2: An Impossible Dream?

It used to be thought that hydrocarbon ionic surfactants were incompatible with dense liquid or supercritical CO2, and fluorination of the chains was necessary to achieve any appreciable solubility. Here it is shown that branching of pendant hydrocarbon chains, especially methylation of the tips, can lead to substantial solubility enhancements in CO2 over normal linear chain hydrocarbon surfactants. In addition, increasing the number of these t-butyl-tipped groups from single-chained, through twin-tailed, to triple-chain surfactants has a profound effect on CO2 compatibility. High-pressure interfacial tension, small-angle neutron scattering, and near infrared spectroscopy have been applied to reveal the effects of surfactant structure on surface activity, aggregation, and solubility in CO2.

Fluorocarbon-hydrocarbon incompatibility in micellar polymerizations

A new approach to micellar polymerization is described. It is well known that hydrocarbons and fluorocarbons exhibit local phase segregation (demixing) owing to mutual antipathy; here this effect is employed in monomer swollen micelles with appropriate combinations of hydrocarbon and fluorocarbon monomers and surfactants. A matrix of these hydro- and fluorocarbon components has been investigated to delineate the effects of H-F antipathy on the outcomes of polymerization reactions to generate nanolatices of different size (and possibly morphology). Phase diagrams, (1)H NMR and small-angle neutron (SANS) data have been generated to characterize the systems, indicating new routes to influence nanolatex formation.