Presidential Green Chemistry Challenge: 1997 Academic Award
Professor Joseph M. DeSimone of the University of North Carolina at Chapel Hill (UNC) and North Carolina State University (NCSU)
Design and Application of Surfactants for Carbon Dioxide
Innovation and Benefits: Professor DeSimone developed new detergents that allow carbon dioxide (CO2), a nontoxic gas, to be used as a solvent in many industrial applications. Using CO2 as a solvent allows manufacturers to replace traditional, often hazardous chemical solvents and processes, conserve energy, and reduce worker exposure to hazardous substances.
Summary of Technology: It has been a dilemma of modern industrial technology that the solvents required to dissolve the environment's worst contaminants themselves have a contaminating effect. Now, new technologies for the design and application of surfactants for carbon dioxide (CO2), developed at UNC, promise to resolve this dilemma.
Over 30 billion pounds of organic and halogenated solvents are used worldwide each year as solvents, processing aids, cleaning agents, and dispersants. Solvent-intensive industries are considering alternatives that can reduce or eliminate the negative impact that solvent emissions can have in the workplace and in the environment. CO2 in a solution state has long been recognized as an ideal solvent, extractant, and separation aid. CO2 solutions are nontoxic, nonflammable, energy-efficient, cost-effective, waste-minimizing, reusable, and safe to work with. Historically, the prime factor inhibiting the use of this solvent replacement has been the low solubility of most materials in CO2, in both its liquid and supercritical states. With the discovery of CO2 surfactant systems, Professor Joseph M. DeSimone and his students have dramatically advanced the solubility performance characteristics of CO2 systems for several industries.
The design of broadly applicable surfactants for CO2 relies on the identification of "CO2-philic" materials from which to build amphiphiles. Although CO2 in both its liquid and supercritical states dissolves many small molecules readily, it is a very poor solvent for many substances at easily accessible conditions (T < 212 °F and P < 4,350 psi). As an offshoot of Professor DeSimone's research program on polymer synthesis in CO2, he and his researchers exploited the high solubility of a select few CO2-philic polymeric segments to develop nonionic surfactants capable of dispersing high-solids polymer latexes in both liquid and supercritical CO2 phases. The design criteria they developed for surfactants, which were capable of stabilizing heterogeneous polymerizations in CO2, have been expanded to include CO2-insoluble compounds in general.
This development lays the foundation by which surfactant-modified CO2 can be used to replace conventional (halogenated) organic solvent systems currently used in manufacturing and service industries such as precision cleaning, medical device fabrication, and garment care, as well as in the chemical manufacturing and coating industries.
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