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The dependence of the water self-diffusion coefficients as well as of the proton spin-lattice and spin-spin relaxation rates on the concentration have been studied in the gelatin-water system and in hydrated native collagen. The bound and free water fractions and the corresponding spinspin and spin-lattice relaxation rates have been determined within the multi-phase water proton exchange model. Various theoretical models for the water proton cross-relaxation to the biopolymer have been studied and the results compared with the observed Larmor frequency dependence of the water proton spin-lattice relaxation rate.

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The frequency and temperature dependences of the proton spin–lattice relaxation rate have been studied in nematic droplets embedded in a solid polymer matrix. The comparison of these data to those for bulk nematic and pure polymer samples shows that cross-relaxation between liquid crystal and polymer protons dominates the liquid crystal relaxation in the MHz frequency region, while at low frequencies the translationally induced molecular rotation becomes important. The cross-relaxation rate is found to be ≈103 s−1 giving an order of magnitude estimate 10−4–10−3 s for the time for which a liquid crystal molecule is bonded to the surface.

The hydrocarbon part of (C 10 H 2 iNH 3 )2CdCl 4 represents a smectic lipid bilayer exhibiting two structural phase transitions in analogy to biomembranes. Single-crystal 13 C NMR and 14 N nuclear quadrupole resonance and x-ray data show that the first transition is connected with a disordering of the polar heads whereas the second represents a partial melting of the lipid chains. A Landau theory describing the melting of bilayer membranes in terms of order parameters used in the theory of liquid crystals has been constructed to explain the obtained results.

2014 La dépendance en température de l'orientation moléculaire des noyaux aromatiques et des chaînes aliphatiques dans la phase cristal liquide colonnaire de l'hexapentyloxy-triphénylène a été déterminée en utilisant la spectroscopie de résonance magnétique nucléaire de haute résolution du 13C. On a trouvé que les chaînes ont une configuration déployée (diablo). Les noyaux et les chaînes sont coplanaires et orientés de telle façon que le champ magnétique extérieur est dans le plan de la molécule. Les noyaux aromatiques sont presque complètement orientés (Sar = 0,85 ± 0,10) et la mobilité des segments de chaîne augmente sensiblement quand la distance au noyau aromatique augmente. Abstract. 2014 The temperature dependence of the molecular ordering of the aromatic rings and the aliphatic chains in the columnar liquid crystalline phase of hexapentoxy-triphenylene has been determined using high resolution proton enhanced 13C NMR spectroscopy. The chains have been found to be preferentially in the extended (diablo) configuration. The rings and chains are coplanar and ordered in such a way that the external magnetic field lies in the molecular plane. The aromatic rings are nearly completely ordered (Sar = 0.85 ± 0.10) whereas the mobility of the chain segments significantly increases with increasing distance from the aromatic core.

The temperature dependences of the second moments M2 of the proton magnetic resonance absorption spectra and of the proton spin–lattice relaxation times T1 of perovskite layer compounds (CnH2n+1NH3)2CdCl4 with n=1–3 and (NH3– (CH2)n–NH3) CdCl4 with n=2−5 have been studied together with the frequency dispersion of T1. The structural phase transitions in these compounds were found to be connected with a change in the state of motion of the alkyl or alkylene groups, i.e., by an interplay of transitions between different N–H−−−Cl hydrogen bonding schemes and the excitation of hindered rotations of the hydrocarbon chains.

35It should be noted that even an extremely small experimental error in the starting C/U02 ratio makes it difficult to attain the UN,,,,,,, composition. Acknowled ment'Iso, M. Ito, an$ A. Ho'shino for the chemical analyses.The writers are grateful to K. Takashima, H. Yoshida, S.