Long range ordered state complex

Figure 8.5 Schematic diagram of state and phase transitions ofstarch note the effect of moisture content and time on the various states. Tg1 Tg2 and Tg3 represent the glass transition at different moisture content levels. A-L and V-structures denote short- and long-range order of amylose-lipid complexes, whereas d.h. order corresponds to short-range B-type structures.

Compared to crystalline materials, the production and handling of amorphous substances are subject to serious complexities. Whereas the formation of crystalline materials can be described in terms of the phase rule, and solid-solid transformations (polymorphism) are well characterised in terms of pressure and temperature, this is not the case for glassy preparations that, in terms of phase behaviour, are classified as unstable . Their apparent stability derives from their very slow relaxations towards equilibrium states. Furthermore, where crystal structures are described by atomic or ionic coordinates in space, that which is not possible for amorphous materials, by definition, lack long-range order. Structurally, therefore, positions and orientations of molecules in a glass can only be described in terms of atomic or molecular distribution functions, which change over time the rates of such changes are defined by time correlation functions (relaxation times). 

NMR studies of metals in sohd state non-metallic materials such as zeolites, inorganic complexes, glasses, coals, polymers, metalloproteins, and RNA have been reviewed. The role of solid state NMR spectroscopy in investigating the structural and functional aspects of these materials with no long range order is evaluated. This overview presents several developments of solid state NMR to the study of a variety of metal containing materials. In particular, the use of the quadrupolar Carr-Purcell-Meiboom-Gill pulse sequence for the acquisition of solid state NMR spectra of quadrupolar nuclei with low natural abundances and low NMR frequencies, and applications of solid state Cd NMR are covered in detail. 

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