AMPHIPHILIC DERIVATIVES OF ALGINATE - EVIDENCE FOR INTRAMOLECULAR AND INTERMOLECULAR HYDROPHOBIC ASSOCIATIONS IN AQUEOUS-SOLUTION

The covalent fixation of a long alkyl chain (C-12) onto a partially esterified derivative of sodium a (PGA) affords an amphiphilic compound which exhibits in aqueous solution the typical properties of hydrophobically associating water-soluble polyelectrolytes. Rheological measurements carried out in the semidilute regime evidence the occurrence of intermolecular hydrophobic interactions, resulting in strongly enhanced viscosity. At high dilution, viscometric data suggest the formation of compact conformations, resulting from intramolecular hydrophobic associations. Fluorescence experiments conducted with pyrene show that polymer concentrations as low as 0.05 % are sufficient to create a hydrophobic microenvironment for this probe. The phenomenon is enhanced upon increasing the ionic strength.