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  • 11
    Electronic Resource
    Electronic Resource
    Synthesis of polypropene-block-poly(ethylene-co-propene) by short-period polymerization with MgCl2-supported Ziegler catalyst (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 16 (1995), S. 247-252 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The short-period polymerization method was successfully applied to the synthesis of a novel diblock copolymer, polypropene-block-poly(ethylene-co-propene). The polymerization was carried out for ca. 0,1 s with a MgCl2-supported Ziegler catalyst. The copolymers obtained showed unimodal curves in gel-permeation chromatography without any peak in the low-molecular-weight region. After extraction with heptane, the fraction of poly(ethylene-co-propene) remained unchanged in the copolymer but disappeared in a commercial so-called block-type copolymer. All the results the formation of polypropene-block-poly(ethylene-co-propene), in which poly(ethylene-co-propene) is chemically linked with polypropene.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1995.030160403
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  • 12
    Electronic Resource
    Electronic Resource
    Study of the chain transfer reaction by hydrogen in the initial stage of propene polymerization (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 16 (1995), S. 651-657 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The chain transfer reaction by hydrogen in the initial stage of propene polymerization with MgCl2-supported Ziegler catalyst was studied by means of the stopped-flow polymerization. The yield and molecular weight of polypropene produced in the initial stage were not affected by hydrogen. Thus, the method was successfully applied to find the region in which hydrogen does not act as a chain transfer reagent. On the other hand, a chain transfer reaction proceeded in the initial stage of polymerization by using Zn(C2H5)2. Furthermore, when the catalyst was treated with Al(C2H5)3 before polymerization, the molecular weight of the produced polymer was decreased by using hydrogen, indicating that it acted as a chain transfer agent for the catalyst modified by pre-treatment.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1995.030160903
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  • 13
    Electronic Resource
    Electronic Resource
    Synthesis of a biodegradable polymeric supramolecular assembly for drug delivery (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 16 (1995), S. 259-263 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel design of a biodegradable carrier for drug delivery was established by constructing a supramolecular assembly of drugs and polymer backbones without any covalent bonds. A biodegradable polyrotaxane was synthesized in which α-cyclodextrins (α-CDs) as drug carriers were threaded onto poly(ethylene glycol) chains which then were capped at each chain end by L-phenylalanine via peptide linkages. The release of α-CDs was observed only when the terminal peptide linkages were degraded.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1995.030160405
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  • 14
    Electronic Resource
    Electronic Resource
    Ethene polymerization with modified-polypropene-supported highly stable Ziegler catalyst (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 25-29 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A modified-polypropene-supported Ziegler catalyst was prepared using polypropene containing a small amount of poly(7-methyl-1,6-octadiene) as a starting polymer for bromination, lithiation, and reaction with TiCl4. The polymerization of ethene was carried out using the catalyst with Al(C2H5)3 in toluene at 60°C up to 100 h. The polymer yield increased linearly with polymerization time, which indicates that the active sites of the modified-polypropene-supported Ziegler catalyst are practically stable without deactivation even for 100 h and are able to propagate further polymerization of ethene.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1996.030170104
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  • 15
    Electronic Resource
    Electronic Resource
    Thermal stability of syndiotactic polypropene (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 18 (1997), S. 157-161 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal stability of syndiotactic polypropene (syn-PP) was investigated by comparison with isotactic polypropene (iso-PP). Heat treatments were carried out in air at 160-220°C for 10-30 min. Under these conditions, molecular weight and molecular weight distribution of syn-PP were almost kept constant, indicating the high stability of syn-PP. Iso-PP was degraded drastically under the same conditions. Thus, it is confirmed that the stereoregularity is one of the dominant factors to determine the stability of PP.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1997.030180213
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  • 16
    Electronic Resource
    Electronic Resource
    Characterization of the differences in the crystallinity from surface to bulk of compression-molded polypropene sheets using attenuated total reflection fourier-transform IR spectroscopy (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 3523-3530 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystallinities of compression-molded polypropene sheets were investigated by applying Fourier-transform (FT)-IR and attenuated total reflection (ATR) FT-IR analyses. Two internal reflection elements, Ge and KRS-5, with an angle of incidence of 45°, were used to obtain the depth profiles of the crystallinity of polypropene sheets from the surface to bulk. The crystallinity in the region from the surface to about 0,7 μm depth was considerably lower than that in bulk. Polypropene sheets with higher comonomer content showed the same tendency, which was enhanced with decreasing molding temperature.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1996.021971103
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  • 17
    Electronic Resource
    Electronic Resource
    Microstructural characterization of polypropene surfaces using grazing incidence X-ray diffraction (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 261-266 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The grazing incidence X-ray diffraction was applied for characterizing the crystalline structure of the outermost layer of polypropene sheets. Even in the outermost surface layer within about 5 nm, the crystalline structure of the a form was confirmed by the X-ray diffraction patterns. The values of a and c for the crystal lattice dimension were almost constant in spite of the variation of surface layer crystallinity, whereas the value of b for the surface layer decreased with increasing crystallinity or decreasing comonomer content of polypropene. This suggests that the density of the crystal increased as a function of crystallinity. Additionally, the value of b for the surface layer was smaller than that of the bulk. It was concluded that the lattice distortion can be ascribed to the residual stress caused by the molding pressure under the higher super-cooling rate.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Multiplicity of molecular weight distribution of polyethene produced with modified-polypropene-supported Ziegler catalyst systems (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 393-399 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular weight and molecular weight distribution of polyethene prepared with a modified-polypropene-supported Ziegler catalyst were investigated in terms of the variation of the polymerization conditions, such as the kind of co-catalyst, its concentration, and polymerization temperature. Ethene polymerization with the catalyst in the presence of triethylaluminium proceeded in heterogeneous system to give a polyethene with extremely broad molecular weight distribution. The result was completely changed upon replacing the triethylaluminium by other alkylaluminium compounds, such as diethylaluminium chloride. Polyethenes with very broad, narrow, bimodal, and multimodal molecular weight distributions were obtained by simply varying the co-catalyst. The molecular weight distributions of polyethenes obtained were also very sensitive to co-catalyst concentration and polymerization temperature. From the results obtained, it is suggested that the modified-polypropene-supported Ziegler catalyst is feasible as a novel candidate for a catalyst system giving polyethenes with controlled molecular weight distributions in a wide range of molecular weight.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Kinetic study of isospecific active sites formed by various alkylaluminiums on MgCl2-supported Ziegler catalyst at the initial stage of propene polymerization (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 1249-1255 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of various kinds of alkylaluminium on the kinetic parameters of the initial stage of propene polymerization with MgCl2-supported Ziegler catalyst was studied by the stopped-flow polymerization method. The active sites concentration ([C*]) decreased drastically with the increase of bulkiness of the alkyl group of the aluminium compound, while the change of the propagation rate constant (kp) was rather small and proportional to the meso pentad fraction of the resulting polypropene. The kinetic parameters, kp(insol) and [C*(insol)], were calculated from the yield and number-average molecular weight of the boiling heptane insoluble fraction. The values of kp (insol) were almost constant, while those of kp depended on the ratio [C*(insol)]/[C*(total)]. The results obtained in this study suggest that isospecific active sites produced by various alkylaluminiums are essentially the same, but the amounts of the active sites formed with a variety of alkylaluminiums are different.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980426
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  • 20
    Electronic Resource
    Electronic Resource
    Thermally switchable polyrotaxane as a model of stimuli-responsive supramolecules for nano-scale devices (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 509-515 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A polyrotaxane consisting of many β-cyclodextrins (β-CDs) and a triblock copolymer of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) capped with bulky end-groups was synthesized as a model of stimuli-responsive supramolecules for nanoscale devices. The polyrotaxane was reversibly soluble-insoluble in water in response to temperature. This was achieved through the assembled and dispersed states of β-CDs along the block copolymer. It is considered that intermolecular hydrogen bondings of β-CDs, as well as the PEG segment length of the copoloymer, are predominant factors for regulating such thermally switchable behavior of the polyrotaxane.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1996.030170803
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