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  • 1
    Electronic Resource
    Electronic Resource
    Spontaneous oscillation of the electrical membrane potential in tri-block copolypeptide membranes composed of L-glutamic acid and L-leucine (1993)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 115 (1993), S. 5902-5906 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00067a002
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and biodegradation of poly(γ-butyrolactone-co-l-lactide) (1996)
    Springer
    Journal of polymers and the environment 4 (1996), S. 205-211 
    Details
    ISSN: 1572-8900
    Keywords: γ-Butyrolactone ; l-lactide ; biodegradable polymer ; hydrolysis ; ring-opening polymerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Biodegradable polyesters were synthesized by ring-opening copolymerization of γ-butyrolactone (BL) and its derivatives withl-lactide (LLA). Although tetraphenyl tin was the main catalyst used, other organometallic catalysts were used as well.1H and13C NMR spectra showed that poly(BL-co-LLA)s were statistical and that their number-average molecular weights were as high as 7×104. The maximum BL content obtained from copolymerization BL/LLA was around 17%. TheT m andT g values of the copolymers showed a gradual depression with an increase in BL content. NoT m was obtained for the copolymers containing more than 13 mol% BL. The biodegradability of the copolyesters was evaluated by enzymatic hydrolysis and nonenzymatic hydrolysis tests. The enzymatic hydrolysis was carried out at 37°C for 24 h using lipases fromRhizopus arrhizus andR. delemar. Hydrolyses by both lipases showed that an increase in BL content of the copolymer resulted in enhanced biodegradability. Nonenzymatic accelerated hydrolysis of copolymers at 70°C was found to increase proportionally to their exposure time. The hydrolysis rate of these copolymers was considerably faster than that of PLLA. The higher hydrolyzability was recorded for the BL-rich copolymers. The copolymerization of γ-methyl-γ-butyrolactone (MBL) or γ-ethyl-γ-butyrolactone (EBL) with LLA resulted in relatively LA-rich copolymers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02067454
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  • 3
    Electronic Resource
    Electronic Resource
    Properties and biodegradability of chain-extended copoly(succinic anhydride/ethylene oxide) (1996)
    Springer
    Journal of polymers and the environment 4 (1996), S. 225-233 
    Details
    ISSN: 1572-8900
    Keywords: Copolyesterether ; succinic anhydride ; chain-extension reaction ; biodegradation ; activated sludge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Chain-extension reactions were carried out using titanium-iso-propoxide (TIP) as a catalyst for a series of polyesters or copolyesterethers with low molecular weights (M n =1500–10,000) synthesized by the ring-opening copolymerization of succinic anhydride (SA) with ethylene oxide (EO). The copolymers having aM n from 25,000 to 50,000 of different properties were obtained. Both the melting point (T m ) and the fusion heat (δH), which indicate the crystallinity of the copolymers, rose with an increase in SA content in the copolymers. Semitransparent films were prepared by compression molding of the copolymers. The biodegradation of the copolymer films was evaluated by enzymatic hydrolysis by lipases and by an aerobic gas evolution test in standard activated sludge. The hydrolyzability of these copolymers by three kinds of lipases was affected by their copolymer composition SA/EO, form, andM n . The copolyesterether (SA/EO=43/57,M n =48,900) was more easily biodegraded by standard activated sludge compared to the polyester (SA/EO=47/53,M n =36,300).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02070691
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Cell growth on poly(vinyl alcohol) hydrogel membranes containing biguanido groups (1994)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 459-462 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A cationic, high-water-content hydrogel membrane composed of poly(vinyl alcohol) (PVA) and poly(allylbiguanido-co-allylamine) hydrochloride (PAB) with positively charged biguanido groups that resemble arginine residues was developed. The PAB was prepared by reacting poly(allylamine) hydrochloride (PAA) with guanyl-O-methyl isourea. PAB/PVA hydrogel membranes were prepared by repeated freezing and thawing. For comparison, hydrogel membranes composed of PAA and PVA were also prepared. The interaction between these hydrogel membranes and mouse fibroblast (L929) was studied by a cell culture method. The PAB hydrogel blend had a relatively low percentage of initial cell attachment. The cell growth on the PAB hydrogel membranes showed a maximum at 5 mol % PAB content that was as high as commercially available plastic films. However, cells on hydrogel membranes with 50 mol % PAB content and 0 mol % PAB content (only PVA) did not seem to grow; neither did the 5/95 PAA/PVA membranes. Water contact angles of hydrogel membranes did not vary with the PAB content. Morphology of the cell attachment was observed by SEM. On the PAB blend hydrogel surfaces, cells were not spindle-shaped and monolayers, but rather cells aggregated in spherical clusters. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820280408
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    Paper (German National Licenses)
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