Influence of alkyl chains length on the conformation and solubilization properties of amphiphilic carboxymethylpullulans

Abstract : The existence of inter- and/or intramolecular interactions in aqueous solutions of hydrophobically modified polysaccharides induces specific macromolecular conformations at the air–solution interface and in the bulk, where hydrophobic microdomains may be formed. The present work focuses on the interfacial and solubilizing properties of amphiphilic pullulans (CMP12C8, CMP7C14, and CMP4C16) differing in the length and percentage of alkyl chains grafted to the anhydroglucose units. The surface tension studies of these polymers evidence a marked difference between the interfacial properties of CMP12C8 on one hand and those of CMP7C14 and CMP4C16 on the other hand. Pyrene fluorescence spectroscopy and benzophenone solubilization experiments demonstrate a similar partition. Increasing alkyl chains length from eight up to 14 or 16 carbons improves the solubilization properties of nonpolar molecules, even though at the same time, the average number of grafted chains per 100 anhydroglucose units is decreased from 12 down to seven and four for the three compounds, respectively.