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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 40 (1998), S. 741-747 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this work, a series of 2,3-O-methylcellulose (MC) with different DS value were prepared. Its phase transition behavior in aqueous solution was studied in terms of DS value, concentration and molecular weight. The the following conclusions were obtained. (1) All the 2,3-O-MC samples show no sol-gel transition in aqueous solution despite the molecular weight. (2) No phase separation was observed for the 2,3-O-MCs with a DS value lower than 1.0, even when the temperature was raised to 95°C. (3) The precipitation temperature is surprisingly different between 2,3-O-MCs. and other MCs possessing comparable total DS value. (4) The precipitation temperature of 2,3-O-MCs depends on the molecular weight rather than on the concentration.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-882X
    Keywords: LiCl/1 ; 3‐dimethy‐2‐imidazolidinone solvent system ; homogeneous cellulose solution ; cellulose acetate ; O‐methylcellulose ; reaction characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In order to elucidate the nature of the LiCl/1,3‐dimethy‐2‐imidazolidinone (DMI) solvent system as one of the homogeneous reaction media of cellulose, cellulose acetate (CA) and O‐methylcellulose (MC) were prepared using this solvent system, and the distribution of substituents within anhydroglucose units was examined by 13C‐NMR. It was found that (i) homogeneous cellulose solutions can be easily prepared by heating 2, 5–12 and 100 parts of weight of cellulose, LiCl, and DMI, respectively, and (ii) the relative reactivity of hydroxyl groups is in the order C‐6 〉 C‐2 〉 C‐3 for both CA and MC. A remarkable feature of this solvent system is that the reaction efficiency in etherification is very high compared with other homogeneous solvent systems.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-882X
    Keywords: O-methylcellulose ; water solubility ; substituents distribution ; regioselective substitution ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of substituent distribution on the water solubility of O-methylcellulose (MC) was re-examined to elucidate the lower limit of the degree of substitution (DS) in water-soluble MC. To this end, a series of 2,3-MCs which are regioselectively substituted at the C-2 and C-3 hydroxyl groups were prepared by homogeneous methylation. It was found that the lower limit for the DS value of water-soluble 2,3-MC was almost the same as that for MCs having even distributions of substituents along the cellulose chain as well as in the anhydroglucose units.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 18 (1997), S. 921-925 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of 2,3-O-carboxymethylcelluloses (CMC's), which are regioselectively substituted at the C-2 and C-3 position, were prepared and their water solubility was examined. It was found that the lower limit for the degree of substitution (DS) value of water-soluble 2,3-O-CMC is about 0.3. This value was almost the same as that of CMC prepared in a slurry of isopropyl alcohol/water with isopropyl chloroacetate and sodium hydroxide, showing that the uniform alkylation is rather important to convert cellulose into water-soluble derivatives.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Previous work from this laboratory has shown that cellobiose octaalkanoate (COA) functions as a thermotropic discotic mesogen, forming a hexagonal ordered columnar phase (Dho). In this work, we prepared the COA-based discotic twin and triplet derivatives and examined the mesomorphic properties of the derivatives by DSC, polarization microscopy and X-ray diffraction. In the former derivative, two cellobiose heptadecanoate (CHD) molecules (monomers) are combined through an alkyl spacer of varying length by ether and ester linkages at the C-1 position of the reducing end units of the monomers. Three CHD molecules having an alkyl spacer are connected with a coupling agent for the latter derivative. The results revealed that (i) all the twin derivatives form a distinct discotic columnar phase, (ii) the thermal stability of the mesophases of the twins is enhanced, compared with that of the monomer, when the length of the flexible spacer is appropriate, (iii) the twins with a relatively short spacer form a discotic rectangular ordered (Dro) phase, while those with a longer spacer form a pseudo-Dho phase, (iv) the triplets also form a discotic columnar mesophase, but not a hexagonal ordered columnar (Dho) phase, (v) the thermal stability of the mesophases of the triplets strongly depends on the chemical nature of coupling cores, and (vi) the packing structures of the cellobiose cores within the columns of both derivatives are markedly different from that of the monomer.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2071-2077 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This study concerns the synthesis of poly(vinyl ether)s (VEs) carrying pendant cellobiose heptadecanoate (CHD) residues and their mesomorphic properties examined by DSC, polarization microscopy and X-ray diffraction. The poly(VE)s were synthesized through cationic polymerization of a CHD-substituted VE, i.e., 10-(vinyloxy)decyl-2,2′,3,3′,4′,6,6′-hepta-O-decanoyl-β-D-cellobioside. From X-ray diffraction analyses, the mesophase of the poly(VE) proved to be closely similar to that of the star-shaped triplet derivative. The mesophase is characterized by the following features; (i) it consists of discotic columns built up by a regular stacking of the pendant CHD residues, (ii) each polymer main chain is presumed to have an extended conformation due to the periodic stacking of the pendant CHD moieties into a columnar structure, and (iii) each polymer molecule independently forms three discotic columns, which surround the main chain, without any intercalation of the CHD pendants originating from different polymer molecules.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1119-1126 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two series of thermotropic polymethacrylate (PM) samples with pendant cellobiose residues and an alkyl spacer (number of carbon atoms n = 4 and 10) were synthesized, and their mesomorphic properties were investigated to elucidate the function of acylated cellobiose moieties as discotic mesogens by differential scanning calorimetry (DSC), polarization microscopy and X-ray diffraction. The PM-4 samples with a short spacer (n = 4) showed two kinds of mesophases in a wide temperature region up to the degradation temperature of the sample, i. e., about 230°C, whereas the PM-10 samples with a long spacer (n = 10) showed a single mesophase between 45 and 135°C. X-Ray diffraction data suggested that both the mesophases formed by PM-4 and PM-10 belong to a kind of discotic columnar phases in which the side chain mesogens form the discotic columns around the polymer backbone.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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