Polymer studies quadrupole relaxation

Cl quadrupole relaxation studies of Cl binding to synthetic polycations and polyampholytes have recently been started [525] and, furthermore, observations of Cl NMR in polyanion (poly(phosphate) and poly(methacrylic acid)) solutions have been reported [526 527]. In Fig. 10.1 are shown the Cl transverse relaxation rates (from line widths of Fourier transform spectra) for solutions of poly(N,N-dimethyl-aminoethylmethacrylate) and poly(methacrylic acid) as a function of the degree of ionization, a, of the polyelectrolyte [525]. (a = 0 corresponds to equivalent concentrations of acid and polymer and a = 1 to equivalent concentrations of base and polymer.) The Cl interaction with the polycation can be seen to have a considerable effect on the relaxation rate the linear decrease for intermediate a-values reflects the gradual titration of the dimethylammonium groups. Quadrupole relaxation studies seem to be well suited for elucidating halide ion -... 

It is well known that nmr is a powerful means for the study of the dynamics of polymer chains both in solution and in the solid state. The relaxation of 13C nuclei has been extensively employed for this purpose in this and other laboratories. I illustrate here a dilferent and particularly intriguing approach which as yet has seen only very limited application to synthetic polymers. This is deuterium quadrupolar echo spectroscopy, as employed in our laboratory by Dr. Lynn Jelinski and her collaborators (20). The presence of the nuclear electric quadrupole lifts the degeneracy of the two deuterium Zeeman transitions, and in the solid state produces a very broad (ca 200 kHz) powder pattern of transitions which can be interpreted to yield very specific motional information for those carbons labelled with deuterium. In Figure 7 are shown spectra of poly (butylene terephthalate) deuterated on the central carbons of the aliphatic chains ... 

The studies to be reviewed below mainly refer to proton or deuteron magnetic resonance in melts or concentrated solutions of polymers of molecular masses close to or above the critical value M. Under such circumstances the predominant spin-lattice relaxation mechanism of protons (spin 1/2) is based on fluctuating dipole-dipole couplings of like spins, that is, we are dealing with the homonuclear case. Deuterons (spin 1), in contrast, possess a finite electric quadrupole moment which is subject to quadrupole coupling to local molecular electric field gradients which is much more efficient than dipolar interactions. 

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