title: 1H NMR study on pre-micellization of quaternary ammonium gemini surfactants.
abstract: Two quaternary ammonium Gemini surfactant series, 12-s-12, ([C(12)H(25)N+ (CH(3))(2)](2)(CH(2))(s).(2)Br(-)) and 14-s-14 ([C(14)H(29)N(+)(CH(3))(2)](2)(CH(2))(s).(2)Br(-)), where s = 2, 3, and 4, have been studied by the use of (1)H NMR in aqueous solution at concentrations below their critical micelle concentrations (CMC) at 25 degrees C. The appearance of a second set of peaks for the 14-s-14 series and the changes in chemical shifts, line widths, and line shapes of the 12-s-12 series with increasing concentration below the CMC are interpreted as evidence for the formation of premicelle aggregates (oligomers) that appear at approximately one-half their CMC values. Self-diffusion coefficients (D) and transverse relaxation times (T(2)) have also been detected and support the results obtained by (1)H NMR.
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Jiang
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Cui
authors.forename: Shi-Zhen
authors.initials: SZ
authors.lastname: Mao
authors.forename: Mai-Li
authors.initials: ML
authors.lastname: Liu
authors.forename: Ping-Ya
authors.initials: PY
authors.lastname: Luo
authors.forename: You-Ru
authors.initials: YR
authors.lastname: Du