A quantitative electron-spin resonance line shape study of the local motion in the micellar and liquid crystalline lamellar phases of the oleoyllysolecithin water system

The experimental electron-spin resonance (ESR) line shapes of the micellar (L1) and lamellar (Lα) phases of the binary system 1-oleoyl-sn-glycero-3-phosphocholine (OlLPC)/water have been interpreted quantitatively using a two-dynamic (TD) model. This dynamic model comprises the local dynamics of Freed’s model [J. Chem. Phys. 55, 5270 (1971); 58, 3185 (1973); 77, 3915 (1982)] and a second Brownian motion referring to the combined effect of the micellar reorientation and the translational motion of the amphiphile molecule along the micellar surface. With this model, we focus our attention on a comparison of the local dynamics between the L1 and Lα phases. It is found from the TD model that the local ordering (λ) and dynamics (τ⊥) of the L1 phase change compared with those of the Lα phase according to λ(L1)≳λ(Lα) and τ⊥(L1)<τ⊥(Lα). The observed lower local ordering in the lamellar phase compared with that in the micellar phase may be interpreted in terms of the different packing constraints of the OlLPC molecule in the two phases.