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71.
Measurements of flow birefringence of cellulose tricarbanilates were carried out on nine fractions (0.27 × 105 < M ≤ 12 × 105) in a temperature range of 55–110°C, with benzophenone as a matching solvent (dn/dc = 0). The ratio of Maxwell constant to intrinsic viscosity, which has been found to be independent of molecular weight for the limiting case of Gaussian molecules, is successfully interpreted as a function of molecular weight in terms of the recent theory of Gotlib and Svetlov (based on the wormlike chain model of Kratky and Porod). From the measurements at 55°C a number of 36.6 monomer units per random link is deduced. This is in accord with results of small-angle x-ray scattering. For the extinction angle curves a clear transition is observed from rodlike to statistical molecules when the molecular weight is increased. At high molecular weights the master curves obtained for anionic polystyrenes and cellulose tricarbanilates coincide. Implications of this observation on the kinetic stiffness of the cellulose tricarbanilate chain are discussed. The intrinsic viscosity-molecular weight relationship is considered. From a comparison with the results of the theory of Eizner and Ptitsyn it is concluded that the cellulose tricarbanilate chain must be highly solvated in benzophenone. 相似文献
72.
Consider two types of translation-invariant functionals and on , and a sequence of functions fn whose corresponding symmetric rearrangements are convergent. We show that fn themselves converge up to translations if either or . These compactness results lead to applications in variational problems and stability problems in stellar dynamics. 相似文献
73.
Frontispiece: Dendronized Hyperbranched Macromolecules: Soft Matter with a Novel Type of Segmental Distribution
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Hiroshi Kamitakahara Arata Yoshinaga Hajime Aono Fumiaki Nakatsubo Dieter Klemm Walther Burchard 《Cellulose (London, England)》2008,15(6):797-801
In the present paper we suggest a new concept to overcome some of the so far unsolved problems of the structure–property relationship
of methylcellulose, the most important nonionic cellulose ether industrially produced in large scale. Not only from the viewpoint
of scientific understanding, but also from that of the peculiar and application-determining behavior, the aggregation in aqueous
solution and phase separation on heating are the most important questions. As a part of the concept, we had prepared amphiphilic
block co-oligomers of tri-O-methylated and unmodified cello-oligosaccharides as structural models of typical sequences in methylcellulose chains. Now
static and dynamic light scattering measurements and transmission electron microscopy (TEM) were carried out using solutions
of the oligomers in water. Ellipsoidal particles with dimensions of about 50 nm for the semi-major axis and of circa 25 nm
for the semi-minor one could be detected. These findings agree with the radii of gyration and the hydrodynamic radii, determined
by static and dynamic light scattering. The data preliminary obtained demonstrate the strong aggregation tendency of block-like
methylated cello-oligosaccharides. 相似文献