REVERSIBLE GEL FORMATION INDUCED BY ION COMPLEXATION .1. BORAX GALACTOMANNAN INTERACTIONS

The cross-linking mechanism involved in the formation of reversible gels in galactomannan-borax systems has been investigated. We studied interactions between borate ion and guaran or (hydroxypropyl)guaran. Borate ions can form several types of complexes with the various hydroxyl groups of the sugar units. To elucidate the structure of the involved complexes, glycoside compounds were used as models. Evidence of the existence of five-membered and six-membered ring monodiol- and didiol-borate complexes has been obtained by **1**1B NMR studies. Complex formation constants were determined at four temperatures from **1**1B NMR spectra.