Phase behavior of mixed polyoxyethylene-type nonionic surfactants in water

Citation
H. Kunieda et al., Phase behavior of mixed polyoxyethylene-type nonionic surfactants in water, J MOL LIQ, 90(1-3), 2001, pp. 157-166
Citations number
18
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF MOLECULAR LIQUIDS
ISSN journal
0167-7322 → ACNP
Volume
90
Issue
1-3
Year of publication
2001
Pages
157 - 166
Database
ISI
SICI code
0167-7322(200102)90:1-3<157:PBOMPN>2.0.ZU;2-W
Abstract
Cloud temperatures, phase behavior, and the structures of liquid crystals w ere investigated in the aqueous systems of homogenous hexaethylene glycol d odecyl ether(C12EO6) and mixed C12EO4-C12EO8,, C12EO2-C12EO8 and C12EO0-C12 EO8. In the mixed surfactant systems, the average polyoxyethylene- (EO-) ch ain lengths are kept constant, the same as C12EO6 The change in cloud tempe ratures is small in all the systems, whereas the phase behavior is successi vely changed with increasing the difference in EO-chain length in the mixtu re. Lamellar liquid crystal is developed in the phase diagrams and it intru des in the two-phase region above the cloud temperature. Hence, the phase p attern of the present mixed surfactant systems resembles that of C12EO5 sys tem, but both cloud point and W+L-alpha region appear at much higher temper ature. Hence, the Hydrophile-Lipophile Balance of the surfactant is not lar gely changed by mixing the surfactants but the SAXS results show that the s urfactant molecules are more tightly packed in the hexagonal and lamellar p hases by mixing. It is considered that when surfactants of different EO-cha in lengths are mixed, the considerable reduction in repulsion between the h ydrophilic moieties takes place and the surfactant molecules are more tight ly packed. (C) 2001 Elsevier Science B.V. All rights reserved.