Synthesis and Solution Chemistry of Dimeric Surface Active Agents - Enhancement of Surface Activity, Solubilization, and Rheology.

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The use of surfactants (short for surface-active-agents) in chemical applications has gained significant and varied interest over the last few decades. In addition to their common use as detergents and emulsifiers, surfactants have been employed as a reaction medium for the synthesis of nanoparticles, improved drug delivery systems, and in new high-performance paints and coatings. Conventionally, surfactants consist of a single hydrophobic tail (generally a hydrocarbon) and a strongly polar or ionic headgroup. Over the past 6 years, our NSERC Discovery Grants (DG) program at StFX University has synthesized novel amphiphiles containing multiple headgroups (so-called gemini and other multi-headed surfactants), utilizing versatile building blocks (e.g., pentaerythritol and amino acids). Positive research outcomes from this program are the link that exists between the chemical modification of the surfactant structure and the change in the solution performance of the surfactant that results. This lab is currently synthesizing surfactants that have superior hard water tolerance (no soap scum and good foaming ability in hard water) and excellent detergency/emulsification properties as a result of this research. Projects undertaken in this lab fall into one or more of the following themes: 1. The synthesis of new surfactants; 2. A fundamental understanding of the molecular nature of the self-assembly process;3. Applications of multi-nuclear nmr spectroscopy in probing the molecular structure of micellar systems and polymer- surfactant complexes; and 4. Microscopic examination of unusual and large surfactant assemblies formed through altering the kosmotropic-chaotropic balance in the surfactant molecules. This NSERC DG funded research will continue to investigate fundamental chemical and commercially important aspects of surfactant aggregation. An area of focus will be the synthesis of asymmetric gemini surfactants (twin-headed, twin-tailed surfactants with an unequal tail length) and related compounds, and the measurement of their solution properties. We will also determine the fundamental solution properties of mixtures of zwitterionic surfactants and gemini surfactants with other surfactants and polymers. The objectives of the program are a better understanding of surfactant chemical structure/performance by understanding the how the variation in the surfactant structure changes the subtle balance of forces responsible for their aggregation into simple, spherical micelles, worm-like micelles, and giant vesicles. UG and Masters's students working on these projects will be trained in surfactant syntheses, have hands-on experience with a 400 MHz nmr, a light scattering instrument, surface tensiometers, rheometers, will build their own ion-specific electrodes, and will be trained in a highly structured, ISO-like research environment.