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  • hydrogels  (2)
  • (heparin-PEO) grafted segmented polyurethaneurea  (1)
  • 1
    Electronic Resource
    Electronic Resource
    “On–Off” Thermocontrol of Solute Transport. I. Temperature Dependence of Swelling of N-Isopropylacrylamide Networks Modified with Hydrophobic Components in Water (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 531-537 
    Details
    ISSN: 1573-904X
    Keywords: thermosensitivity ; hydrogels ; N-isopropylacrylamide ; interpenetrating polymer networks ; surface deswelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The swelling in water, as a function of temperature, of two series of N-isopropylacrylamide (NIPA Am) polymer networks was studied. In the first series, n-butylmethacrylate (BMA) was copolymerized with NIPA Am, and in the second, polytetramethylene ether glycol (PTMEG) was incorporated into NIPAAm network as a chemically independent interpenetrating network. With increasing BMA content in the poly(NIPAAm-co-BMA) network, the gel collapse point was lowered and the gels deswelled in a more gradual manner with increasing temperature. In the interpenetrating polymer networks (IPN) system, the gel collapse point was not significantly changed by the amount of incorporated PTMEG. In DSC thermograms of swollen samples, the shape and onset temperature of the endothermic peak corresponded to the gel deswelling behavior and gel collapse point. The temperature dependence of equilibrium swelling in water was shown to be a function of the gel composition in both network series. The synthesized networks formed a dense surface layer as the temperature increased past the gel collapse point. This dense layer retarded water efflux and thereby resulted in water pockets at the membrane surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015871732706
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrogels: Swelling, Drug Loading, and Release (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 283-290 
    Details
    ISSN: 1573-904X
    Keywords: hydrogels ; swelling ; loading ; release kinetics ; functional polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrogels have been used by many investigators in controlled-release drug delivery systems because of their good tissue compatibility and easy manipulation of swelling level and, thereby, solute permeability. The desired kinetics, duration, and rate of solute release from hydrogels are limited to specific conditions, such as hydrogel properties, amount of incorporated drug, drug solubility, and drug–polymer interactions. This review summarizes the compositional and structural effects of polymers on swelling, loading, and release and approaches to characterize solute release behavior in a dynamic state. A new approach is introduced to compensate drug effects (solubility and loading) with the release kinetics by varying the structure of heterogeneous polymers. Modulated or pulsatile drug delivery using functional hydrogels is a recent trend in hydrogel drug delivery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015887213431
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of SPUU-PEO-heparin graft copolymers (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1725-1737 
    Details
    ISSN: 0887-624X
    Keywords: (heparin-PEO) grafted segmented polyurethaneurea ; surface modification ; nonthrombogenic surface ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new synthetic approach for the preparation of segmented polyurethaneurea (SPUU)-PEO-Heparin graft copolymers (B-PEO-Hep) has been developed. The procedure involved the coupling of hexamethylene diisocyanate (HMDI) to soluble Biomer® (B) through an allophanate/biuret reaction. The free isocyanate (NCO) groups attached to Biomer® were then coupled to PEO terminal hydroxyl groups to form PEO grafted Biomer® (B-PEO). B-PEO free hydroxy groups were modified with HMDI to introduce terminal isocyanate groups. The NCO functionalized B-PEO was then coupled to heparin (Hep) functional groups (—OH, —NH2) producing B-PEO-Hep graft copolymer. Synthetic intermediates were confirmed by FTIR, NCO group determination, and toluidine blue heparin assay. Physical characterization techniques, such as contact angle measurements, water swelling, light scattering measurements, and DSC thermal analysis, detailed properties of the graft copolymer containing covalently bound heparin. This new heparinized copolymer can be applied as a coating on other existing blood contacting surfaces without changing bulk properties. The heparin bioactivity observed attests to the usefulness of this new procedure as a coating to improve the blood compatibility of blood-contacting surfaces.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080291206
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    Paper (German National Licenses)
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