Alkylglucosides with isoprenoid-type hydrophobic chains-effects of hydrophobic chain size on the aqueous phase behavior

Aqueous phase diagrams were constructed for two new alkylglucosides with isoprenoid-type hydrophobic chains, viz. 1-O-beta-(3,7-dimethyloctyl)-D-glucopyranoside, beta-Glc(Ger), and 1-O-beta-(3,7,11,15-tetramethylhexadecyl)-D-glucopyranoside, beta-Gle(Phyt). In a low concentration regime, from 0.17 to 34 wt.% beta-Glc(Ger), the beta-Glc(Ger)/water system exhibits two phase, a dilute (L-1(dil)) and a concentrated isotropic phase (L-1(conc)), coexistence region. Above about 62 wt.% beta-Gle(Ger), an Lalpha phase is formed. The extent of the L-1(dil) + L-1(conc) two-phase region decreases as temperature increases and totally disappears above 130degreesC, exhibiting an upper critical temperature. The beta-Glc(Phyt)/water system exhibits an Lot phase above 78 wt.% surfactant below which, an Lalpha + water two-phase region appears. One notable feature of these compounds is their low values of Krafft-eutectic temperature, T-K, e.g. the value of T-K for beta-Glc(Phyt) is below 0degreesC although the total number of carbon atoms in the hydrophobic chain is as large as 20. (C) 2003 Elsevier Ireland Ltd. All rights reserved.