PHASE-BEHAVIOR OF THE SYSTEMS N-DECANEPHOSPHONIC ACID WATER AND N-DODECANEPHOSPHONIC ACID/WATER/

The n-decanephosphonic acid/water and n-dodecanephosphonic acid/water systems were studied by differential scanning calorimetry, hot stage p olarized light microscopy, and FT-IR spectropetry. There is a rich pol ymorphism: in both systems there are three liquid crystalline phases ( lamellar L(alpha) and L(beta) and an inverse cubic phase) plus the iso tropic Liquid and two solid phases. One of the solids is an ordinary c ristalline phase and the other is a waxy crystal in which the polar he adgroup network is rigid and ordered but in which the alkyl chains are partially fluid and disordered. The water in these systems exists in two distinct forms: water bound to the headgroups and water which is e ffectively free. The polymorphism of the heptyl and octyl analogues ha s been studied by Klose et al.