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 mice llar (L1) and lamellar (L(alpha) phases of the binary system 1-oleoyl- sn-glycero-3-phosphocholine (O1LPC)/water have been interpreted quanti tatively using a two-dynamic (TD) model. This dynamic model comprises the local dynamics of Freed's model [J. Chem. Phys. 55, 5270 (1971); 5 8, 3185 (1973); 77, 3915 (1982)] and a second Brownian motion referrin g to the combined effect of the micellar reorientation and the transla tional motion of the amphiphile molecule along the micellar surface. W ith this model, we focus our attention on a comparison of the local dy namics between the L1 and L(alpha), phases. It is found from the TD mo del that the local ordering (lambda) and dynamics (tau(perpendicular-t o)) of the L1 phase change compared with those of the L(alpha) phase a ccording to lambda(L1) > lambda(L(alpha)) and tau(perpendicular-to) (L 1) < tau(perpendicular-to) (L(alpha)). The observed lower local orderi ng in the lamellar phase compared with that in the micellar phase may be interpreted in terms of the different packing constraints of the O1 LPC molecule in the two phases.