Order and mobility

Komfield J.A., Spiess H.W., Nefzger H., Hayen H., and Eisenbach C.D. Deuteron NMR measurement of order and mobility in the hard segments of a model polyurethane, Macromolecules, 24, 4787, 1991. Meltzer A.D., Spiess H.W., Eisenbach C.D., and Hayen H. Motional behaviour within the hard domain of segmented polyurethane A NMR study of a triblock model system. Macromolecules, 25, 993, 1992. 

Solid state 2H NMR parameters are almost exclusively governed by the quadrupole interaction with the electric field gradient (EFG) tensor at the deuteron site.1 8 The EFG is entirely intramolecular in nature. Thus molecular order and mobility are monitored through the orientation of individual C-2H bond directions. Therefore, 2H NMR is a powerful technique for studying local molecular motions. It enables us to discriminate different types of motions and their correlation times over a wide frequency range. Dynamics of numerous polymers has been examined by solid state 2H NMR.1 3,7,9 Dynamic information on polypeptides by NMR is however limited,10 26 although the main-chain secondary structures of polypeptides in the solid have been extensively evaluated by 13C and 15N CP/MAS NMR.27,28... 

Srinivasan, G, Kyrlidis, A., McNeff, C., and Muller, K., Investigation on conformational order and mobility of diamondbond-C18 and Cl 8-alkyl modified silica gels by Fourier transform infrared and solid-state NMR spectroscopy, J. Chromatogr. A, 1081, 132, 2005. 

The order and mobility of a labeled flexible alkyl spacer in the linear thermotropic polymeric nematic liquid crystal poly(2,2 -dimethyl-4,4 -dioxyazoxybenzenedodecanedioyl-dj0) (poly[oxy(3-methyl-1,4-phenylene)azoxy 2-methyl-1,4-phenylene)oxy(1,12-dioxo-1,12-dodecanediyl-d2oll) is explored with deuterium NMR. The quadrupol splittings of the spacer methylene segments in the nematic melt of the polymer are reported as a function of the temperature and are contrasted with observations on model compounds solubilized in a nematic solvent. 

Liquid crystals (LC) represent truly fascinating materials in terms of their properties, their importance for the fundamental understanding of molecular self-assembly, and their tremendous success in commercial applications [1, 2], Liquid crystals can be considered as a state of matter which in a unique way combines order and mobility [3-8]. The constituent molecules of LC phases are sufficiently... 

It is obvious that this volume cannot be fully comprehensive, but at least it should provide a rough overview, covering some of the important subjects in the field of liquid crystal design and self-assembly. Nevertheless, I hope the present volume will be highly informative and inspiring for chemists and physicists who are interested in developing new materials based on the unique combination of order and mobility provided by the LC state. 

Order and Mobility are two basic principles of mother nature. The two extremes are realized in the perfect order of crystals with their lack of mobility and in the high mobility of liquids and their lack of order. Both properties are combined in liquid crystalline phases based on the selforganization of formanisotropic molecules. Their importance became more and more visible during the last years in Material science they are a basis of new materials, in Life science they are important for many structure associated functions of biological systems. The main contribution of Polymer science to thermotropic and lyotropic liquid crystals as well as to biomembrane models consists in the fact that macromolecules can stabilize organized systems and at the same time retain mobility. The synthesis, structure, properties and phototunctionalization of polymeric amphiphiles in monolayers and multilayers will be discussed. 

D. J. Gundlach, Y. Y. Lin, T. N. Jack-son, S. F. Nelson, and D. G. Schlom, Pentacene organic thin-film transistors - Molecular ordering and mobility, IEEE Electron Device Lett. 18(3), 87-89 (1997). 

Intrinsically, the presence of any solute alters the environment it seeks to probe. However, spectroscopic observations of neat cholesteric compounds allow undisturbed local environments to be discerned. Such observations, although scant, have focussed on the ramifications to raesophase structure, order, and mobility when solvent molecular structure is altered. They indicate, for instance, that the length of an alkyl side chain at C17 of the steroidal backbone does affect the important physical properties which define a solute environment. 

Figures 4-5). Sorption was reversible, and was not affected by a lag of up to 60 days between sorption and desorption (e.g. Figure 4). Fitted parameters for 29 column experiments for which good convergence was obtained for the first-order and mobile-immobile models are presented in Table III. Equilibrium-model parameters are presented for an additional 11 experiments. The full data sets for these experiments can be found in Szecsody (8). 

That order and mobility are by no means very closely correlated is evident from the existence of glasses, which represent highly supercooled liquids. They are hard and brittle, but possess no definite crystalline structure. The randomness of the molecular arrangement is about the same as that in liquids, but they are not necessarily entirely devoid of certain kinds of order, as is suggested by the characteristic conchoidal fracture which is often shown. 

The forms observable in the world about us depend in an important degree upon the ways in which molecules remain free in the gaseous state or agglomerate together, and upon the kinds of order and mobility possessed by the condensed systems which they form. Only less important is the degree in which these condensed systems themselves are able to interpenetrate and mix. 

Liquid crystals (LCs) combine order and mobility on a molecular level and are important both in material and life science [1-9]. Different liquid crystalline phases have provided new methods for the design of supramolecular materials [10-13]. Nematic phases have found widely commercial applications as displays for computers and telecommunications [14], lamellar, coltrmnar, micellar, and bicontinuous cubic phases and even more complicated new phases have also found wide applications as advanced materials [12, 15-17]. 

Liquid crystals (LCs) simultaneously exhibit the anisotropic property of crystalline solids and flow property of liquids. In the liquid crystalline phase, the molecules diffuse like in liquids but they maintain some degree of orientational order while doing so. The combination of order and mobility in LCs makes them fascinating and promising for practical applications. LCs exhibit extreme sensitivity to small external perturbations such as electric field, magnetic field, and surface effect. The most common and commercial application of LCs is in flat panel LC displays... 

Shaposhiukova, V. V, Salazkin, S. N., Matedova, I. A., Petrovskii, P. V. Polyarylenetherketones. Investigation of Approaches to Synthesis of Amorphous Blockpolymers in Abstracts of the 4-th International Symposium Molecular Order and Mobility in Polymer Systems. - St. Petersburg. -. 121. 

NMR technique, especially solid state NMR spectrometry, has been frequently used in investigations of the order and mobility of acyl chains within the lipid bilayers. The NMR study of the quadrupole sphtting of deuterons located along the lipid chain permitted to gain information on molecular motions of lipids. For this aim, selectively deuterated lipids have been prepared. 7V-stearoyl sphingomyelin (Figure 7) was deuterium-labelled on different positions of both the sphingosine and the stearoyl chains to capture its motion in membranes. 

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. 

Surfactant molecules are amphiphilic and associate together in aqueous solution to form various structures micelles, microemulsions, vesicles, lyotropic liquid crystalline phases. In each case, their alkyl chains group together and their polar heads form a layer which separates them from the water. The laws governing this self-assembly involve subtle combinations of the two principles, order and mobility. Some fascinating illustrations are provided by the cell membrane in biological systems. In this case, order and mobility are related to the structure of functional units made up of lipids and proteins [6.10]. Such examples could only encourage chemists to carry out novel syntheses which would produce molecules capable of self-assembly. 

Order and mobility are key properties of conducting materials that display a variety of complex functions and are basic properties of many devices such as liquid crystalline displays or chemical sensors. Later, we will show how the combination of order and mobility may be applied to conducting polymers. 

In addition to complete, one-step fusion, it is possible that some order is retained during a phase transition of the first order. In this case, mesophases are formed as shown in Figure 8. These are phases of intermediate order and mobility... 

It has been shown that the sol-gel materials can be used as host matrices for a variety of biological molecules (7-77). The dopant biomolecules reside in the porous network of these sol-gel composite materials as a part of nanostructured architecture. The unique nanostructured assembly of such sol-gel composites is characterized by biomolecules enclosed in the nanopores of the material. The bioparticles arranged as part of sol-gel composites are characterized by intermediate order and mobility, as opposed to the higher degrees of order available in solids or the pronounced mobilities present in solution media. In other words, the properties of both the solid and solution phases prevail in sol-gel environment. In spite of general similarity in reaction chemistry with macroscopic solution based discipline, variation in overall reaction kinetics can be observed as a direct consequence of encapsulation. Usually it is the interactions of the dopant molecules with the sol-gel matrix that determine the reaction pathways a particular system undergoes. Such a nanostructured system utilizes the properties of spatially isolated molecules in a solvent-rich environment necessary for stability of the biomolecules. 

---