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  • Polymer and Materials Science  (25)
  • Wiley-Blackwell  (25)
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of biodegradable poly(L-lactic acid-co-D,L-mandelic acid) with relatively low molecular weight (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 2407-2415 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A homopolymer of L-lactic acid (LA), which was synthesized by direct polycondensation in the absence of a catalyst at 200°C, is crystalline, in contrast to the homopolymer of D,L-mandelic acid (MA) which is amorphous. Poly(LA-co-MA), obtained under the above conditions, is amorphous over a wide range of composition from 15 to 100 mol-% of monomeric units of MA. The in vitro degradation mechanism of these homopolymers shows a parabola-type degradation pattern for poly(LA) and no degradation throughout an experimental period of 15 weeks for poly(MA). In poly(LA-co-MA) the degradation mechanism leads to a typical S-type degradation pattern, which may be divided into two processes, initial swelling at the surface of the matrix without degradation (induction period), followed by the erosion of oligomers produced by degradation of the main chain in the swollen state.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021901007
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of degradable terpolymers responding to external stimuli such as pH, ionic strength and temperature (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 715-722 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Degradable copolymers which respond to external stimuli such as pH, ionic strength, and temperature were successfully prepared by direct polycondensation of L-lactic acid (LA), D,L-mandelic acid (MA), and 3-(p-hydroxyphenyl)propionic acid (HPPA) without the use of a catalyst at 200°C by bubbling nitrogen through the solution. The molecular weights of the copolymers obtained were relatively low because of the low polymerizability of MA and HPPA, e. g., number-average molecular weight M̄n ≦ 2100 and weight-average molecular weight M̄w ≦ 4100. Poly{(L-lactic acid)-co-(D,L-mandelic acid)-co-[3-(p-hydroxyphenyl)propionic acid]} (poly(LA/MA/HPPA)) with a composition of the monomeric units (in mol-%) LA:MA:HPPA = 80:10:10 showed rapid degradation after a lag time of 5 h within 48 h from the start of the test, in M/15 phosphate buffer solution (pH 7,2) at 37°C. With increasing pH and temperature, the rate of degradation was markedly accelerated.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930317
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  • 3
    Electronic Resource
    Electronic Resource
    Low-molecular-weight copolymers composed of L-lactic acid and various DL-hydroxy acids as biodegradable carriers (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 2571-2577 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Biodegradable copolymers of L-lactic acid (L-LA) and DL-α-hydroxy acids with relatively low molecular weights, for example L-LA/DL-lactic acid (DL-LA), L-LA/DL-α-hydroxybutyric acid (DL-HBA), L-LA/DL-α-hydroxyisovaleric acid (DL-HIVA), and L-LA/DL-α-hydroxyisocaproic acid (DL-HICA), were synthesized by quantitative direct copolycondensation without catalysts at 200°C. The in vitro degradation, which was evaluated by measuring the weight loss of these copolymers in M/15 phosphate buffer solution (pH 7,2) without enzymes at 37°C, is strongly dependent on the kind and molecular weight of these copolymers, resulting in the formation of different degradation patterns such as parabola type (L-LA/DL-HBA system), linear type (L-LA/DL-LA system), and S type (L-LA/DL-HIVA and L-LA/DL-HICA systems).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021901022
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  • 4
    Electronic Resource
    Electronic Resource
    In vivo characteristics of low-molecular-weight copoly(L-lactic acid/DL-hydroxyisocaproic acid) with parabolic-type and S-type degradation pattersn (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 731-736 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An amorphous copolyester of L-lactic acid (LA) and DL-hydroxyisocaproic acid (HICA) with a number-average molecular weight (Mn) of 1600-4800 was synthesized by direct copolycondensation in the absence of catalysts, in order to develop a biodegradable carrier for drug delivery systems. The in vivo degradation pattern was changed into an S-type from a parabolic-type with an increase in molecular weight of copolyester. A luteinizing hormone-releasing hormone agonist, des-Gly10-[D-Leu6]-LH-RH ethylamide, was incorporated into a fine cylindrical copolyester formulation by the so-called melt-pressing technique. When the S-type degradable and releasable copoly(LH/HICA) (70/30 mol-%) formulations with Mn = 2200 were implanted subcutaneously in the back of rats, the most reasonable serum drug level was observed during the first 15 weeks period, keeping constant at approximately 3,5 ng/ml.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910401
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  • 5
    Electronic Resource
    Electronic Resource
    Direct copolymerization of L-lactic acid with γ-butyrolactone in the absence of catalysts (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 1553-1559 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The copolymerization of L-lactic acid (LA) with γ-butyrolactone (BL), performed without catalyst at 200°C under nitrogen in order to obtain a relatively low-molecular-weight copolymer, proceeds via direct condensation between linear LA and linear 4-hydroxybutyric acid produced by hydrolysis of the cyclic BL. The copolymers were characterized with respect to the copolymerizability (13C NMR spectroscopy), composition (1H NMR spectroscopy), molecular weight (terminal group analysis and gel permeation chromatography), and crystallinity (differential scanning calorimetry). The copolymerizability of BL is low, e. g., the contents of BL units in the copolymers were found to be 12, 16, and 19 mol-% for initial BL contents in the monomer feed of 30, 50, and 70 mol-%, respectively, in which copoly(LA/BL) is composed of blocks of lactyl units separated by single γ-oxybutyryl unit.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021900707
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and in vitro degradations of low-molecular-weight copolyesters composed of L-lactic acid and aromatic hydroxy acids (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 2077-2082 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: L-lactic acid (LA) was copolycondensed with various aromatic hydroxy acids such as p-hydroxybenzoic acid (HBA), p-hydroxyphenylacetic acid (HPAA), and p-3-(hydroxyphenyl)propionic acid (HPPA) in the absence of catalysts, in order to investigate the copolymerizability and in vitro degradation. The results of 1H NMR spectroscopy and gel permeation chromatography (GPC) showed that the reaction proceeds quantitatively, but the molecular weight of the copolyesters is relatively low. The in vitro degradation pattern of copoly(LA/HPPA) was changed into an S-type from a parabolic-type with increasing HPPA content in the copolyester, in contrast to only parabolic-type for both copoly(LA/HBA) and copoly(LA/HPAA).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910910
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  • 7
    Electronic Resource
    Electronic Resource
    Nature of polymer matrix of immobilized enzyme composites obtained by radiation polymerization of bifunctional monomers and its effect on the enzymatic activity (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 1831-1836 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cellulase was immobilized on a porous polymer matrix which was formed by radiation polymerization of bifunctional monomers such as poly(ethylene glycol) diacrylates (1), and the nature of the porous polymer matrix and its effect on the enzymatic activity was studied. The porous structure of the polymer matrix was found to change markedly with the monomer concentration and irradiation temperature. The formation of the porous structure shows a discontinuous change in the temperature region of -10 to -40°C, due to the change in polymerization phase and mechanism. The enzymatic activity is strongly related to the pore size, the degree of hydration of the polymer matrix, and the particle size of the composite. The degree of hydration of the polymer matrix varies with the number of oxyethylene units in the monomers 1.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021840908
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of phosphoric acid on the polycondensation of ε-caprolactone with δ-valerolactone and biodegradation of their copolyesters (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1067-1072 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolycondensation of ε-caprolactone (CL) and δ-valerolactone (VL) was performed in the presence and absence of phosphoric acid, in order to clarify the competition between the ring-opening reaction of lactones and the polycondensation of linear compounds produced by this reaction. The gel permeation chromatography data showed that the monomer peaks remained in the system even after 7 h from start of the reaction when polymerized in the absence of phosphoric acid and, on the contrary, in the presence of phosphoric acid the peaks disappear perfectly within 1 h. The weight-average molecular weights (M̄w) of poly(CL-co-VL), obtained by copolycondensation with and without phosphoric acid at 200°C for 1 h, were approximately 540 and 8900, suggesting that phosphoric acid markedly accelerates not only the rate of ring-opening but also the rate of copolycondensation. On the other hand, the biodegradation of the copolyesters obtained is characterized by the action of a lipase-type enzyme, showing a typical parabolic-type degradation pattern.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920505
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  • 9
    Electronic Resource
    Electronic Resource
    Iodine-initiated, solid-state copolymerization of tetraoxane with 1,3-dioxolane in the presence of methylal. VI. Studies on copolymer composition (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 3395-3409 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In order to elucidate the mechanism of copolymerization of tetraoxane-1,3-dioxolane, the consumption rate of 1,3-dioxolane was measured by using gas chromatography, and the copolymer composition was determined by high-resolution NMR spectroscopy and differential scanning calorimetry. It was found that 1,3-dioxolane is rapidly consumed in the early stage of copolymerization if 1,3-dioxolane is added at once. The copolymer thus obtained is characterized by a heterogeneous distribution of 1,3-dioxolane in the copolymer chain. However, if 1,3-dioxolane is added continuously during the progress of the copolymerization, the distribution and content of 1,3-dioxolane in the copolymer chain was found to be very homogeneous.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070231123
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  • 10
    Electronic Resource
    Electronic Resource
    Immobilization of mortierella vinacea cells by radiation polymerization (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 295-301 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Immobilization of Mortierella vinacea cells, which contain active α-galactosidase, by radiation polymerization at low temperatures was studied. The durability of the enzymatic activity of the immobilized cells was examined by repeating the batch enzyme reaction. The enzymatic activities of the immobilized cells obtained with hydrophilic monomers was affected by the concentrations of the cells and monomer in which optimum conditions were observed. The enzymatic activity of the immobilized cells obtained with hydrophilic monomer was compared to that of hydrophobic monomers. Michaelis constants of the immobilized cells varied with monomer concentration. The effect of addition of porous solid substances on the immobilization of the cells was studied.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1983.070280125
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