Guest Selectivity in Complexation of β-Chitin

Abstract

Guest selectivity in complexation of β-chitin with small molecules was studied. Since amines are strong agents for β-chitin complexation, selectivity for various amines was studied first. Of three isomers of phenylenediamine, the para isomer formed a complex, while ortho and meta isomers did not. The selectivity for linear aliphatic amines was examined for equimolar mixtures of various combinations, i.e., primary−secondary−tertiary amines of C6 main chain; C5 diamine and C6 monoamine; and C6 monoamine and C8 monoamine. The results showed a clear selectivity for primary amine over secondary and tertiary, diamine over monoamine, and longer alkyl chain over a shorter one. On the basis of such selectivity, complexation by guest incorporation from solution was established. This procedure allowed β-chitin complexation with high melting point compounds, to which pure liquid treatment was not applicable. By the solution treatment, complexes with acrylamide, p-aminobenzoic acid, and d-glucose were successfully prepared. In this method, even low-solubility combinations such as acrylamide/benzene (0.3% (w/w)) were found effective, presumably because of high chemical potential of solutes in the solution. The wide variety of guest species thus attained is expected to be useful in applications such as drug delivery or composite material preparation.