| Since the introduction of synthetic surfactants in the early 20th century, their use has continually increased and, as a result, surfactants have become one of the highest volume synthetic chemicals produced globally. Indeed, the current estimated volume of productions is over 12 Mt/a with an expected annual growth of 3-4%. The majority of surfactants are used in detergent formulations that have a use-phase on the order of minutes. Post-use, the surfactants are released directly into the water supply, making surfactants one of the largest and most mobile classes of synthetic molecules in the world. This enormous volume of production and release creates a vast interface with the environment and, as a result, surfactants have been implicated in a number of environmental and human health impacts, ranging from eutrophication to endocrine disruption.;Surfactants, which are here not meant to include soaps, have historically been produced using either petrochemical or oleochemical feedstocks. In recent years, however, oleochemicals and a variety of other renewable substrates, such as carbohydrates, amino acids, and organic acids, have been of increasing interest as feedstocks for surfactant production. This interest in renewable feedstocks is driven at least in part by the realization that fossil fuel reserves are finite and alternative resources must be identified, however several studies have also shown that the use of renewable feedstocks can significantly reduce the CO2 emissions associated with the production and use of surfactants.;While the full replacement of petrochemical surfactants may be desirable from a CO2 abatement standpoint, considerations such as cost and performance will ultimately determine the success of a surfactant technology, and the expansion in the use of renewable chemicals must be implemented with care in order to avoid adverse environmental impacts associated with land and water use. To this end, next generation renewable surfactant technologies must be derived from robust and sustainable feedstocks, must be produced efficiently, and must have physicochemical properties that are comparable or superior to petrochemical surfactants, all while maintaining a low production cost.;This research introduces a new class of surfactants that have the potential to address all of these criteria. The surfactants described herein are described generally as carbohydrate-based C-glycosides and fall into two series, linear and cyclic. The design of these series aims to overcome performance limitations associated with previous generation carbohydrate based surfactants -- specifically pH stability and synthetic selectivity -- through use of a C-C bond between the hydrophilic "head" group and the "lipophilic" tail. These molecules are prepared using a novel synthetic route that proceeds through a Knoevenagel-type condensation, followed by an enamine-catalyzed aldol condensation. The resulting process adheres closely to the principles of green chemistry, including considerations such as atom economy, step economy, and a reliance on renewable feedstocks. In addition to a more robust design, these surfactants have demonstrated desirable surface-active properties and show promising environmental performance metrics with regard to aquatic toxicity and biodegradability.;The dissertation will cover both the production and performance of these Cglycoside surfactants. Also presented is a review of the current status of renewable surfactant production, as well as a perspective on the future of renewable chemical production, in general, as it pertains to algae. Taken as a whole, the dissertation aims to explore how renewable surfactants have been produced historically, and how they can be produced into the future, using the examples of the linear and cyclic C-glycosides as an active study in the application of green design principles. |
