N. Mahieu et al., ANALYSIS OF C-13 NUCLEAR-SPIN RELAXATION PARAMETERS, INCLUDING ROTATING-FRAME RELAXATION-TIMES, IN A SERIES OF MICELLIZED SODIUM ALKANOATES, Journal of physical chemistry, 97(37), 1993, pp. 9513-9518
Sodium octanoate, nonanoate, decanoate, undecanoate, and dodecanoate,
dissolved in D2O, have been investigated in monomeric and micellar sta
tes by means of C-13 longitudinal relaxation times at the following me
asuring frequencies: 22.6, 50, 75, and 100.4 MHz. For the highest surf
actant concentrations available, C-13 relaxation times in the rotating
frame have also been measured according to an improved methodology. D
ata have been analyzed within the framework of the two-step model, tak
ing into account the lack of precise knowledge of monomer proportion.
Parameters pertaining to the two-step model, namely, correlation times
associated with slow and fast motions and order parameters, are discu
ssed with regard to the surfactant chain length. It is demonstrated th
at C-13 measurements performed at a single frequency are as well able
to yield these parameters, provided that they include the longitudinal
relaxation time (T1), the nuclear Overhauser effect factor (NOEF), an
d the relaxation time in the rotating frame (T1rho).