Solid-State NMR Investigation

To identify the processes that are suppressed by the antiplasticisers, NMR studies are required [12]. The t /2 contact times in PET/TPDE blends, shown in Fig. 17, are lower than those in pure PET. They do not change with temperature until 70 °C. As t /2 is mostly sensitive to ring flips, the number of ring flips in the polymer has been determined for PET/TPDE blends (Fig. 18). Within the accuracy of the experiments, no ring flips are observed between 25 and 70 °C. 

The investigation of pure PET and PET/additive blends by combining dynamic mechanical analysis, dielectric relaxation and solid-state NMR techniques, leads to a clear attribution of the molecular processes involved in the ft relaxation of PET, as well as an understanding of the effect of an antiplasticiser additive  

Bisphenol A polycarbonate, BPA-PC (Fig. 25), has an unusual toughness among the amorphous thermoplastics, which has led to considerable industrial development. As early as the 1960s studies [8] were performed to understand the molecular origin of such a behaviour and to relate it to the secondary transition occurring around - 100 °C. 

In order to investigate the molecular motions involved in this transition and, in particular, the nature of the associated cooperativity, it is interesting to consider not only BPA-PC, but also tetramethyl bisphenol A polycarbonate, TMBPA-PC, (Fig. 25) as well as copolymers of BPA and TMBPA carbonates, and compatible blends of BPA-PC and TMBPA-PC. 

Furthermore, the effect of miscible small molecule additives, antiplasticisers, on the secondary transition, is worth analysing in order to reach a deeper understanding of the involved molecular motions. 

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Similar to the case of 2,4,6-trialkylaminoborazines, the latter linkage mechanism predominates according to liquid and solid-state NMR investigations.54... 

Solid-State NMR investigation of formation of mesoporous thin films and powders... 

Solid-state NMR investigation of formation ofmesoporous thin films and powders 951... 

Aisenbrey C, Bertani P, Bechinger B (2010) Solid-state NMR investigations of membrane-associated antimicrobial peptides. Methods Mol Biol 618 209-233... 

Peng, L. and Grey, C.P. (2008) Diphosphine probe molecules and solid-state NMR investigations of proximity between addle sites in zeolite HY. Micropor. Mesopor. Mater., 116, 277-283. 

Solid-state NMR investigation of complexes Cp An(CH3)2 and Cp Th(CH2C6H5)3 on various support materials basically revealed three C CP... 

In a study of 2,2 - and l,2 -biindenyl dilithium (6, 7, Scheme 1), C solid state NMR investigations were used, in combination with solution NMR studies and calculations, to obtain information about the existence of so-called triplet structures . Triplet structures are alkali metal complexes of dianions that arrange in a structure akin to dimers in Figure lb and were found by X-ray crystallography for the TMEDA complex of the dilithium salt of 9,9 -bifluorene (Figure 13) . This kind of structure has been proposed to account for the unexpected small difference in the first and second pXj value in some systems, where ApXa is found to be less than 1 pXa unit. ... 

Mayer C. and Lukowski G., Solid state NMR investigations on nanosized carrier systems, Pharm. Res., 17, 486, 2000. 

The technique of solid-state NMR used to characterize supported vanadium oxide catalysts has been recently identified as a powerful tool (22, 23). NMR is well suited for the structural analysis of disordered systems, such as the two-dimensional surface vanadium-oxygen complexes to be present on the surfaces, since only the local environment of the nucleus under study is probed by this method. The nucleus is very amenable to solid-state NMR investigations, because of its natural abundance (99.76%) and favourable relaxation characteristics. A good amount of work has already been reported on this technique (19, 20, 22, 23). Similarly, the development of MAS technique has made H NMR an another powerful tool for characterizing Br 6nsted acidity of zeolites and related catalysts. In addition to the structural information provided by this method direct proportionality of the signal intensity to the number of contributing nuclei makes it a very useful technique for quantitative studies. 

All the solid-state NMR investigations described provide a detailed description of the intramolecular motions performed in glassy BPA-PC. Unfortunately, they do not give any information on the intermolecular cooperativity that could be associated with some of them. 

In conclusion, it is unambiguous from the solid-state NMR investigations that phenyl ring motions are involved in the mechanical ft transition of BPA-PC. Additional support for this statement comes from the fact that the position and shape of the mechanical dynamic loss, G", can be well simulated by using the activation parameters and the Williams-Watts exponent deduced from the analysis of the phenyl ring motions [34], as shown in Fig. 53. 

VanderHart, D.L., Asano, A., and Gilman, J.W. 2001. Solid-state NMR investigation of paramagnetic nylon-6 clay nanocomposites. 1. Crystallinity, morphology, and the direct influence of Fe3+ on nuclear spins. Chemistry of Materials 13(10) 3781-3795. 

Fichera MA, Braun U, Schartel B, Sturm H, Knoll U, Jager C, Solid-state NMR investigations of the pyrolysis and thermo-oxidative decomposition products of a polystyrene/red phosphorus/magnesium hydroxide system. J. Anal. Appl. Pyrolysis 2007 78 378-386. 

Solid State NMR Investigations of Metal Carbonyl Complexes... 

Kohl, S.D., Paul, T.J. and Rice, J.A. (2000) Solid-state NMR investigation of dual-mode sorption to soil organic matter. Abstracts of Papers of the American Chemical Society, 220, 2-ENVR. 

Based on a detailed numerical analysis of the perspectives for solid-state NMR investigations of uniaxiaUy oriented membrane proteins in the 30-40 kDa regime,we have recently explored experimental aspects of such studies with focus on PISEMA and chemical shift correlated (HETCOR) spectra for the seven-transmembrane... 

There is clear evidence for a distinctive influence of hydrogen bonds on carbonyl carbons in peptides. Wei et al. performed solid state NMR investigations on 17 different polypeptides with known structure. They found a correlation of the 21 tensor component (using the convention > 22 > 33) with the N O hydrogen bond distance ... 

The index k runs over all measured values of the intensity I. This equation does not contain the index i of the experimental chemical shift, because to the intensity at some points of the spectrum may consist of contributions from several nuclear sites. On the other hand, we can only analyze spectra in which the intensities are not biased by experimental conditions such as cross polarization effects. Furthermore, the method only seems to make sense in solid state NMR investigations with broad overlapping lines. 

R247 B. Bechinger, Solid-State NMR Investigations on the Structure and Topological Equilibria of Polypeptides Associated with Biological Membranes , Phys. Chem. Chem. Phys., 2000, 2, 4569... 

Brunner, E. and Sternberg, U. (1998) Solid-state NMR investigations on the nature of hydrogen bonds, J. Prog. NMR Spectrosc. 32, 21-57. 

A more recent formula of ACP was provided by Heughebaert (1977) and Heughe-baert and Montel (1982) as Ca9(P()4)6 x(I lP()4)x(OI l)x. The presence of HP042-ions in the structure of ACP was confirmed by solid-state NMR investigation (Jager, Maltsev and Karrasch, 2006). 

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