COLLOIDAL PROPERTIES OF AQUEOUS BIVALENT-METAL DODECYLPOLY(OXYETHYLENE)SULFATES AND HEXADECYLPOLY(OXYETHYLENE)SULFATES(I)

Effects of alkyl chain length, oxyethylene chain length, and various gegenions on the colloidal properties of surfactant type CmH2m+1(OC2H4)nSO41/2M have been studied. The results are summarized as follows. (1) Krafft points of CmH2m+1(OC2H4)nSO41/2M (m = 12, 16) are depressed by an increase in oxyethylene chain length (n); therefore this surfactant type can be used in hard water as well as in the presence of heavy metal ions. (2) Foam drainage and creaming of O/W emulsion (benzene-0.5 wt% aqueous surfactant, 1:1 in volume) are remarkably retarded by an increase in alkyl chain length of the calcium salts from 12 to 16, while those properties of the aqueous sodium salts are not so affected. (3) A viscoelasticity develops in the dilute micellar solutions of bivalent metal alkylpoly(oxyethylene)sulfates the alkyl chain length of which is longer than 16, e.g., C16H33SO41/2M (M = Cu, Mn, Ca), C16H33(OC2H4)nSO41/2M, and C18H37SO41/2Cu. The viscosity of the micellar solutions of these surfactants is high and non-Newtonian. On the other hand, the viscoelasticity does not develop in the micellar solutions of bivalent metal salts of lower homologs and sodium salts [CmH2m+1(OC2H4)nSO4Na (m = 12, 16; n = 1, 2, 3) and CmH2m+1SO4Na (m = 12, 14, 16, 18)] over the concentration range up to 5-10 wt%. A possible mechanism of the characteristics of the aqueous C16H33(OC2H4)nSO41/2M solutions has been discussed. © 1979 Academic Press, Inc.