3-Deoxy-s-alkyl-d-glucose derivative micelle formation, CMC and thermodynamics

Abstract

We have studied micelle formation of two series of D-glucose amphiphilic derivatives: 3-deoxy-S-alkyl-1,2-O-isopropylidene-α-D-glucofuranose, marked MAG-S_n and 3-deoxy-S-alkyl-D-glucopyranose, marked GLU-S_n, where n is the carbon atom number of the alkyl chain R in the alkyl group (R=n-C_nH_2n+1; n=8, 12, 16, 18). CMC in water and corresponding surface tension γ have been determined at 25°, 30°, 40° and 50°C by the Wilhelmy plate method. Results show that surface tension is not much altered, either by alkyl chain length or by free hydroxyl group number (2 for MAG-S_n series; 4 GLU-S_n series), whereas these parameters have a great influence on CMC values. Experimental determination of free energy, enthalpy and entropy of micellization shows that micelle formation is an entropic phenomenon (T ΔS _m>ΔH _m); the monomer association is easier for GLU-S_n type than for MAG-S_n one (ΔH _m(MAG-Sn)>ΔH _m(GLU-Sn)); the interactions between hydrophilic heads and water molecules are greater for GLU-S_n compounds than for MAG-S_n ones (ΔS _m(MAG-Sn) > ΔS _m(GLU-Sn)). Quantitative influences of both the alkyl chain length and the free hydroxyl group number, on CMC correlations and on thermodynamics data have been studied. The results are very close to those reported for the corresponding 3-O-alkyl D-glucose and 3-O-acyl-D-glucose derivatives.