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  Home > JCE Print > Journal of Chemical Education > Issues > 2005  > July  >
In the Classroom
JCE DigiDemos: Tested Demonstrations
Demonstrating Encapsulation and Release: A New Take on Alginate Complexation and the Nylon Rope Trick
Andrienne C. Friedli and Inge R. Schlager
Department of Chemistry, Middle Tennessee State University, Murfreesboro, TN 37132

checked by Stephen W. Wright
Pfizer Global Research and Development, Groton, CT 06340

Cover
July 2005
Vol. 82 No. 7
p. 1017
Abstract
Three variations on a classroom demonstration of the encapsulation of droplets and evidence for release of the interior solution are described. The first two demonstrations mimic biocompatible applications of encapsulation. Reversible formation of capsules from aqueous solutions of sodium alginate, a negatively charged polysaccharide derived from kelp, is shown by cross-linking with Ca2+ ions and decomplexation with monovalent ions or a chelating agent. Rapid release of citric acid from a complex coacervate of alginate with chitosan, a positively charged polysaccharide derived from oyster shells, is compared with slow release from capsules strengthened with an outer membrane cross-linked with Ca2+. A third encapsulation exercise exploits the irreversible interfacial polymerization of diamine and diacid chloride to form membranes and illustrates the detection of diamine release from the capsule using an indicator.
Supplement
Notes for the instructor are available.
*  Contents JCE2005p1017W.doc (Microsoft Word)
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*  Citation
 Friedli, Andrienne C.; Schlager, Inge R. J. Chem. Educ. 2005 82 1017.
*  Keywords
 Acids / Bases; Applications of Chemistry; Biotechnology; Carbohydrates; Consumer Chemistry; Demonstrations; Interdisciplinary / Multidisciplinary; Membranes; Polymer Chemistry; Second-Year Undergraduate; Upper-Division Undergraduate
*  History
 Created:
Last Updated:		 May 31, 2005
June 8, 2005
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