MOLECULAR REDESIGN OF EXPANDED POLYSTYRENE TO ALLOW USE OF CARBON-DIOXIDE AS A FOAMING AGENT .1. REVERSIBLE BINDING OF CO2

Environmental concerns, associated with the production of expanded pla stics using hydrocarbon blowing agents, have spurred interest in envir onmentally-friendly technology by which cellular materials, particular ly expanded polystyrene, can be produced. Consequently, we have explor ed the possibility of using styrene-based, amino-functional copolymers to generate expandable systems, which would rely solely on CO2 as a b lowing agent. Carbon dioxide is an attractive foaming agent in that it can be readily extracted from the air, is nonflammable, and exhibits low toxicity. Using a styrenic copolymer, functionalized with ethylene diamine (EDA), the results of this study show that aminated polymers a re capable of reversibly binding weakly acidic gases, CO2 in particula r. While the reaction products (polymer-bound zwitterions) are stable under ambient conditions, decarboxylation can be thermally induced cle anly and easily. Work underway in our laboratory shows that microporou s, as well as nonporous EDA-functional copolymers, are effective, ther mally-reversible sorbents for acid gases. Furthermore, preliminary res ults show that these materials may also find potential applications in facilitated transport membrane technology. (C) 1993 John Wiley & Sons , Inc.