Determination of the complete order matrix of the alpha methylene segment of potassium palmitate

Abstract

The orientational order of the methylene segment adjacent to the head group in the lamellar liquid crystalline phase of potassium palmitate/D2O was investigated using multinuclear magnetic resonance. Dipolar and quadrupolar couplings were obtained from the 1H, 13C, and 2H N.M.R. spectra of potassium palmitate-d31 and 1-13C-2,2-H2- potassium palmitate-d29 dispersed in lamellar liquid crystalline phases as a function of temperature. In order to observe 1H-1H dipolar couplings, a spin echo (Π/2-t1/2-Π—t1/2-echo) was used to remove heteronuclear dipolar couplings to the chain deuterons. A refocusing pulse applied simultaneously to the 13C spins allowed observation of the heteronuclear 1H-13C dipolar couplings in the carbon-13 labelled compound. The complete orientational order matrix of the alpha methylene segment was determined from the dipolar and quadrupolar couplings. As the temperature is decreased from 110°C to a temperature just above the gel-liquid crystalline phase transition (45°C), the principal or...