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Role of quaternary bromides in changing the solubilization site of n ‐heptylamine in cationic micellar solutions
Author(s) -
Kumar Sanjeev,
Sharma Daksha
Publication year - 2003
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-003-0279-9
Subject(s) - chemistry , bromide , cationic polymerization , salt (chemistry) , solvent , alkyl , viscosity , pulmonary surfactant , inorganic chemistry , micelle , medicinal chemistry , polymer chemistry , aqueous solution , organic chemistry , biochemistry , physics , quantum mechanics
Newtonian flow conditions were adopted to take viscosity measurements at 30°C of solutions of cationic surfactants (cetyltrimethylammonium bromide, C 16 TAB, and tetradecyltrimethylammonium bromide, C 14 TAB) with the addition of n ‐heptylamine (C 7 NH 2 ) and quaternary salts (tetra‐ n ‐propylammonium bromide, Pr 4 NBr; tetra‐ n ‐butylammonium bromide, Bu 4 NBr; tetraamylammonium bromide, Am 4 NBr; tetra‐ n ‐octylammonium bromide, Oc 4 NBr; tetra‐ n ‐butylphosphonium bromide, Bu 4 PBr; tetraphenylphosphonium bromide, Φ 4 PBr; n ‐propyltriphenylphosphonium bromide, PrΦ 3 PBr 3 ) by having either a fixed C 7 NH 2 or salt concentration and varying the other. Systems containing a comparatively higher Bu 4 NBr content showed a dramatic decrease in viscosity at higher C 7 NH 2 concentration. Further, the viscosity‐salt concentration profiles of 0.1 M C 16 TAB solutions containing fixed C 7 NH 2 concentrations showed a peaked behavior. The peak positions and salt contents at the peaks were dependent on the length of the alkyl part of the particular salt and the connecting atom (N or P) but independent of the nature of the surfactant and C 7 NH 2 concentration. The behavior is discussed in the light of a change in the solubilization site of C 7 NH 2 caused by the presence of quaternary salts. Cavities in the quaternary salts present in the bulk solvent are proposed to be the new sites of solubilization.