Presidential Green Chemistry Challenge: 2005 Academic Award
Professor Robin D. Rogers of the University of Alabama
A Platform Strategy Using Ionic Liquids to Dissolve and Process Cellulose for Advanced New Materials
Innovation and Benefits: Professor Rogers developed methods that allow cellulose from wood, cloth, or even paper to be chemically modified to make new biorenewable or biocompatible materials. His methods also allow cellulose to be mixed with other substances, such as dyes, or simply to be processed directly from solution into a formed shape. Together, these methods can potentially save resources, time, and energy.
Summary of Technology: Major chemical companies are currently making tremendous strides towards using renewable resources in biorefineries. In a typical biorefinery, the complexity of natural polymers, such as cellulose, is first broken down into simple building blocks (e.g., ethanol, lactic acid), then built up into complex polymers. If one could use the biocomplexity of natural polymers to form new materials directly, however, one could eliminate many destructive and constructive synthetic steps. Professor Robin D. Rogers and his group have successfully demonstrated a platform strategy to efficiently exploit the biocomplexity afforded by one of Nature’s renewable polymers, cellulose, potentially reducing society's dependence on nonrenewable petroleum-based feedstocks for synthetic polymers. No one had exploited the full potential of cellulose previously, due in part to the shift towards petroleum-based polymers since the 1940s, difficulty in modifying the cellulose polymer properties, and the limited number of common solvents for cellulose.
Professor Rogers's technology combines two major principles of green chemistry: developing environmentally preferable solvents and using biorenewable feedstocks to form advanced materials. Professor Rogers has found that cellulose from virtually any source (fibrous, amorphous, pulp, cotton, bacterial, filter paper, etc.) can be dissolved readily and rapidly, without derivatization, in a low-melting ionic liquid (IL), 1-butyl-3-methylimidazolium chloride ([C4mim]Cl), by gentle heating (especially with microwaves). IL-dissolved cellulose can easily be reconstituted in water in controlled architectures (fibers, membranes, beads, flocs, etc.) using conventional extrusion spinning or forming techniques. By incorporating functional additives into the solution before reconstitution, Professor Rogers can prepare blended or composite materials. The incorporated functional additives can be either dissolved (e.g., dyes, complexants, other polymers) or dispersed (e.g., nanoparticles, clays, enzymes) in the IL before or after dissolution of the cellulose. With this simple, noncovalent approach, Professor Rogers can readily prepare encapsulated cellulose composites of tunable architecture, functionality, and rheology. The IL can be recycled by a novel salting-out step or by common cation exchange, both of which save energy compared to recycling by distillation. Professor Rogers's current work is aimed at improved, more efficient, and economical syntheses of [C4mim]Cl, studies of the IL toxicology, engineering process development, and commercialization.
Professor Rogers and his group are currently doing market research and business planning leading to the commercialization of targeted materials, either through joint development agreements with existing chemical companies or through the creation of small businesses. Green chemistry principles will guide the development work and product selection. For example, targeting polypropylene- and polyethylene-derived thermoplastic materials for the automotive industry could result in materials with lower cost, greater flexibility, lower weight, lower abrasion, lower toxicity, and improved biodegradability, as well as significant reductions in the use of petroleum-derived plastics.
Professor Rogers's work allows the novel use of ILs to dissolve and reconstitute cellulose and similar polymers. Using green chemistry principles to guide development and commercialization, he envisions that his platform strategy can lead to a variety of commercially viable advanced materials that will obviate or reduce the use of synthetic polymers.