Micellar aggregates and hydrogels from phosphonobile salts.

The aggregation properties of novel bile acid analogs-phosphonobile salts (PBS)-have been studied. The critical micellar concentration of 23 and 24-phosphonobile salts were measured using fluorescence and 31P NMR methods. All the ten synthesized phosphonobile salts formed gels at different pH ranges in water. The pH range at which individual PBSs could gelate water was narrow and influenced by the number and conformation of hydroxyl groups. A reversible thermochromic system has been developed (with 23-phosphonodeoxycholate at pH 3.3), which changes color upon gelation. The investigation of the first hydrogels derived from trihydroxy bile acid analogs 1 and 6 was made using fluorescence, 31P NMR, X-ray crystallography, circular dichroism and SEM. The present studies reveal that the gel network consists of a chiral, fibrous structure possessing hydrophobic interiors.