Deuterium NMR of synthetic polymers

The unique capabilities of solid-state deuteron NMR (as well as experiments with N and result from the ability to assess ordering and mobility of individual bonds in a solid material. One can specifically examine the molecular mechanisms that determine bulk properties. This ability has motivated deuteron studies of such fundamental issues as the nature of the glass-transition [10-18] interactions in blends and mixtures [19-26], the molecular ordering and dynamics of crystalline materials [10,11,27-31] dynamics of elastomers [32-45], dielectric properties [46,47] and mechanical spectroscopy [48-51]. New experiments continue to be tied to methods development, particularly in the areas of multi-dimensional NMR [10,11,46, 52-61]. Recently, deuteron NMR has been employed in the characterization of new materials, for example for new liquid crystalline polymers [62-84], 

The objectives in this chapter are to describe, with examples, the group of experiments that is now available for study of a new material with deuteron NMR. The focus is upon methods for the characterization of order and mobility in the crystalline state or below Tg, which is our own interest. To be comprehensive, the literature of experiments associated with networks and liquid crystalline materials have been referenced. Examples are taken from the study of the conducting polymer poly(p-phenylene vinylene) carried out in the laboratory of F.E. Karasz at the University of Massachusetts [85-89]. Special attention is also given to several recent experiments from the laboratories of G. Zachmann [31], A. English [92-97] and H.W. Spiess [10, 11, 46, 53]. The focus is upon the means and criteria that motivate one to choose deuterium NMR for characterization. 

The quadrupole splitting depends upon the relative orientation of a principal axis system (PAS, unit vectors x, y and z) fixed in the C-D bond and the magnetic field vector, Bq. The values Qyy, Q z are quadrupole tensor frequency components H- Qyy H- Q z = 0) associated with each principal axis and they are the quadrupole splittings, Av, which result when is aligned 

When (x,y,z) are expressed in spherical coordinates, 0 and I , a more familiar equation (8.2) results [8]  

Data about chain alignment and reorientation must usually be obtained by modelling or simulation of the lineshape, and usually, data from several different experiments are required to yield an unambiguous conclusion. An exception involves the more recent multi-dimensional experiments, described in section 8.5 [53, 59], that are designed to yield the appropriate data graphically or with simple calculation. Even with 2-D spectroscopy, if multiple motions are present or if diffusion is also present, there remains a requirement to model the data. 

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