Solid-like domain

Figure 1 Schematic representation of the 13C (or 15N) spin-lattice relaxation times (7"i), spin-spin relaxation (T2), and H spin-lattice relaxation time in the rotating frame (Tlp) for the liquid-like and solid-like domains, as a function of the correlation times of local motions. 13C (or 15N) NMR signals from the solid-like domains undergoing incoherent fluctuation motions with the correlation times of 10 4-10 5 s (indicated by the grey colour) could be lost due to failure of attempted peak-narrowing due to interference of frequency with proton decoupling or magic angle spinning.

The major contribution to Rpp comes from the intermediate wavenumber— that is, from immediate neighbors. In this wavenumber regime, F(q, t) will have the characteristic of either the solid- or the liquid-like domain. Thus the calculated friction will have only two distinct values, that of the solid-like domain and that of the liquid-like domain. The expression of the self-diffusion is now given by... 

The network structure of gels is generally highly heterogeneous from the structural and dynamic points of view. The existence of solid-like domains from the cross-linked region is characteristic of the formation of the gel network. Such a domain in polysaccharide gels is ascribed to formation of cross-links due to the physical association of chains adopting an ordered conformation. It is now obvious that the secondary structure of such ordered polysaccharide chains is readily determined on the basis of the conformation-... 

Fig. 24.8. NMR spectra of agarose gel. Liquid-like domain (top) and solid-like domain (bottom) (Ref. [19]).

It is now obvious that NMR is a unique technique for the analysis of both the conformation and dynamics of polysaccharides in solutions, solids and gels. Especially, it is very useful to distinguish between the liquid- and solid-like domains by use of DD- and CP-MAS techniques. In addition, a systematic study of a converison diagram among polymorphs by a series of physical treatments is especially useful in order to clarify whether the polysaccharide chain under consideration takes a single or multiple chain both in the solid and in the gel. 

The REDOR 13C echo spectra of two different PMA/[l-13C]Leu/[15N]Leu samples are shown in Figure 10. Signals from the enriched carboxyl carbon of leucine are sharp at all concentrations. Apparently, even at the lowest concentration, the leucine molecules are not well dispersed throughout the polymer, but instead are clustered in small, ordered, crystalline-like domains. The doubling of the carboxyl signal is also seen for pure, crystalline leucine and is attributable to the detailed packing of the leucine molecules in the solid state. 

Dynamic parameters for heterogeneous systems have been explored in the liquid, liquid like, solid like, and solid states, based on analyses of the longitudinal or transverse relaxation times, chemical exchange based on line-shape analysis and separated local field (SLF), time domain 1H NMR, etc., as summarized in Figure 3. It is therefore possible to utilize these most appropriate dynamic parameters, to explore the dynamic features of our concern, depending upon the systems we study. 

Domain formation in binary mixtures of a polymerizable lipid and non-polymerizable lipid is well established for diacetylenic lipids. The rigid diacetylenic unit facilitates the formation of enriched domains in the condensed phase of monolayers or the solid-analogous phase of bilayers. Since diacetylenes polymerize most readily in solid-like states, most studies have focused on conditions that favor domain formation. Only in the case of a mixture of a charged diacetylenic lipid and a zwitterionic PC was phase separation not observed. Ringsdorf and coworkers first reported the polymerization of a phase-separated two-dimensional assembly in 1981 [33], Monolayer films were prepared from mixtures consisting of a diacetylenicPC (6) (Fig. 5) and a nonpolymerizable distearoyl PE (DSPE). 

The calculated self-consistent MCT values of the viscosity and the friction for the solid-like region are found to be about two orders of magnitude larger than those of the same for the liquid-like domain, and the expressions (252) and (253) reduce to... 

This packing effect is due solely to the geometry of the diemical decoration of the substrate and has not been observed for other geometries, which is for, say, alternating strip-like domains composed of different solid materials (see Figs. 5.8). 

Bercegol, et al. have recently discovered an anisotropic solid phase that coexists with the LE phase in pure 12-NBD stearic acid. (At room temperature, the labeled acid, unlike stearic acid, exhibits an LE-LC transition.) Fluorescence microscope studies show that the phase forms needle-like domains, which polarization studies demonstrate are optically anisotropic. The corresponding dipole moment is perpendicular to the long... 

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