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Two kinds of regioselectively substituted cellulose derivatives, i.e., 6-O-triphenylmethylcellulose (6TC) and 2,3-di-O-acetyl-6-O-triphenylmethylcellulose (2,3Ac6TC), were prepared via cellulose. In these samples, C-6 position hydroxyls in the anhydroglucose units (AGU) along the cellulose chain were selectively substituted by the hydrophobic triphenylmethyl groups, but C-2 and -3 position hydroxyls remained in 6TC or were substituted completely by O-acetyls in 2,3Ac6TC. Their chain dynamics in polar solvents, dimethyl sulfoxide (DMSO) and N,N-dimethylacetamide (DMAc), in dilute solution were investigated by dynamic light scattering in the viewpoint of cluster formation. The results were compared with those of cellulose diacetates (CDA) in DMAc where three hydroxyls in the AGU were statistically substituted up to 2.44 by O-acetyls but hydroxyls at C-6 positions remained predominantly. It was found that 6TC and 2,3Ac6TC formed a dynamic structure about 10 times larger than single chains and that the structure would be a temporary and local association due to concentration fluctuations (dynamic structures) which were originated from the hydrophobic interactions between intermolecular triphenylmethyl groups. The dynamics and structures were in clear contrast to those of CDA where a solvent-mediated hydrogen bonding between intermolecular C-6 position hydroxyls was essential to cluster formation. The present structures were so weak as to dissipate easily under low shear field.

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Molecular dynamics has been studied by broadband dielectric relaxation spectroscopy in the Sm-A, Sm-B, and Sm-E phases (Sm denotes smectic) of a homologous series of nonchiral stilbenes. An assignment of modes is presented based on their dependence on temperature and molecular length, and, as far as they obey the Arrhenius law, their activation energy has been determined. In general, reorientations of entire molecules around their short axis are active, whereas reorientations of entire molecules around their long axis are locked out in the Sm-E phase of shorter homologs, yet intramolecular reorientations of polar sites have been established. Strong evidence is presented for an interdependence of reorientations of entire molecules around the short and long axes within the biaxial Sm-E phase of longer homologs.

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Crystalline features of cellulose microfibrils in the cell walls of Glaucocystis (Glaucophyta) were studied by combined spectroscopy and diffraction techniques, and the results were compared with those of Oocystis (Chlorophyta). Although these algae are grouped into two different classes, by the composition of their chloroplasts for instance, their cell walls are quite similar in size and morphology. The most striking features of their cellulose crystallites are that they have the highest cellulose I(alpha) contents reported to date. In particular, the I(alpha) fraction of cellulose from Glaucocystis was found to be as high as 90% from (13)C NMR analysis. The mode of preferential orientation of cellulose crystallites in their cell walls is also interesting; equatorial 0.53-nm lattice planes were oriented parallel to the cell surface in the case of Glaucocystis, while the 0.62-nm planes were parallel to the Oocystis cell surface. Such a structural variation provides another link to the evolution of cellulose structure, biosynthesis, and its biocrystallization mechanism.

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The cyanogen bromide (CNBr) activation method was adopted to link collagen molecules onto the surface of cellulose and poly(vinyl alcohol) (PVA) films via covalent bonding. The amount of bound protein was determined by the ninhydrin method and found to be 1.0 microgram/cm2 for the native collagen and 0.6 microgram/cm2 for the denatured collagen. The amount of bound protein was larger for cellulose than PVA. When p-toluene-sulphonyl chloride was used to activate the cellulose film, this activation method was found to be effective in grafting the collagen as well. The cellulose film was found to become brittle and weak after activation with CNBr, but the PVA films was not. This might be due to the difference in the extent of crosslinking between cellulose and PVA films, as demonstrated by the change in degree of swelling and solubility of both the activated films.

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Blood compatibility has been studied for hydrophilic polymers such as poly(vinyl alcohol) (PVA), its derivative, and polyethylene grafted with water-soluble monomers. The surfaces in contact with electrolyte solutions have been characterized by measuring the zeta potentials. The study of plasma protein adsorption on these polymers has revealed that bovine serum albumin as well as bovine serum fibrinogen adsorbs to a lesser extent as the hydrophilicity of the polymers increases. Platelet deposition and fibrin formation, examined using platelet-rich plasma, have been found to take place less significantly on PVA as well as sodium acrylate- and acrylamide-grafted polyethylene than on nongrafted and acrylic acid-grafted polyethylene. Ex vivo experiments with canine whole blood have shown that formation of thrombus on PVA is less than on siliconized glass but increases upon heat treatment which reduces the hydrophilicity. When PVA tubes of about 1 mm diameter are anastomosed to the carotid artery of rat, the patency rate is found to depend strongly on the anastomotic technique. From the results on the zeta potential and the experiments in vitro and ex vivo it can be concluded that the material having a surface from which solvated, neutral chains are extended into the outer aqueous phase may exhibit excellent resistance to thrombus formation.

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