NMR of Liquid Crystals and Micellar Solutions

Tiddy, G. J. T., "NMR of Liquid Crystals and Micellar Solutions, Chem-... 

This chapter presents a summary of manuscripts published in the perissod of June 2011-June 2012 focusing on the use of NMR techniques to elucidate the microstructure and dynamics of self-assembling systems. In section 2 reviews and articles on general methods and models have been included. In section 3 the papers on thermotropic and lyotropic liquid crystals, phospholipids, vesicles and bicelles have been covered. Section 4 has been devoted to micellar solutions including ionic and non ionic surfactant systems, polymer amphiphiles and mixed amphiphiles systems. 

In a liquid crystalline system there is a rapid molecular motion which will to some extent average out the quadrupole interaction. The residual interaction gives rise to NMR spectra analoguous to the one shown in Figure 5. A theoretical treatment of the quadrupolar effects in micellar solutions and amphiphilic liquid crystals have been published by Wennerstrom et al. (57), showing that eqs. 16 and 17 will be very much the same for this case as for the rigid solids (eqs. 18 and 19). 

It is quite noticeable that these figures are very close to those known for melted paraffins of similar chain lengths. Then the development of NMR studies of deuterated moleoules and of NMR permitted to show that the amplitude of the deformations are about the same in all structures, ordered liquid crystals as well as in disordered micellar solutions. Thus there does not appear any definite correlation between one structure and the molecular behavior in it. The chains are about equally disordered in all structures, in spite of important changes of interfacial curvature and mean area per molecule at the interface. 

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