Electrolyte-induced phase separation and charge reversal of cationic zwitterionic micelles.
The solution properties and anion recognition selectivity of the N-dodecyl-N,N,N',N',-tetramethyldiethylenediammonio-propane sulfonate bromide (DEPB) and N-dodecyl-N,N,N',N',-tetramethyl-1,3-propylenediammonio-propane sulfonate bromide (DPPB) micelles have been studied. These micelles have similar properties except for the phase behavior induced by coexistent anions. The addition of ClO4(-) or I(-) to aqueous DEPB causes phase separation, and further addition results in the dissolution of the separated phases. In contrast, no phase separation occurs for DPPB. Charge reversal of the micelles occurs during the addition of the anions. The difference in the phase behavior between DEPB and DPPB comes from the different sizes of the micelles; the addition of ClO4(-) allows the formation of large aggregates of DEP (~50 nm in diameter).
Aoki
Takeshi
T
Department of Chemistry, Tokyo Institute of Technology, Tokyo, Japan.
Harada
Makoto
M
Okada
Tetsuo
T