EFFECTS OF HEADGROUP STRUCTURE ON THE INCORPORATION OF ANIONS INTO SULFOBETAINE MICELLES - KINETIC AND PHYSICAL EVIDENCE

Zwitterionic micelles of (tetradecyldialkylammonio) propane-, butane- and pentanesulfonate increase the rate of reaction of Br- with methyl naphthalene-2-sulfonate, MeONs, but this reaction is largely suppresse d by addition of NaClO4. The NMR line width of Cl-35 in ClO4- increase s very sharply on incorporation into micelles of tetradecyldimethylamm onio propanesulfonate, SB3-14. The N-14 line width of SB3-14 also incr eases significantly under these conditions, but there is no evidence f or strong interactions with Na-23(+). Aggregation numbers, N-agg, of S B3-14 increase modestly with increasing [SB3-14], but not with the oth er surfactants. The increase is greater with added NaClO4, but NaOH, N aCl and NaNO3 have little effect on N-agg. Interactions of the anions with the micelles are treated with equations of the form of the Langmu ir isotherm, and binding parameters estimated kinetically and conducto metrically agree. Second-order rate constants of the reaction of Br- w ith MeONs at micellar surfaces are similar in sulfobetaine and cationi c micelles. The reaction of I- with MeONs is also accelerated by micel les of SB3-14.