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  • 1
    Electronic Resource
    Electronic Resource
    Ion binding properties of poly(ethylene oxide)-based networks in dioxane and toluene (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 1819-1824 
    Details
    ISSN: 0887-624X
    Keywords: poly(ethylene oxide) networks ; alkali picrates ; alkali ion binding ; poly(crown ether) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Binding constants of alkali picrates to poly(ethylene oxide)-based networks were measured spectrophotometrically in dioxane at 25 and 40°C. The networks were synthesized from aliphatic tri- or tetrafunctional isocyanates and α,ω-diamino-poly-(ethylene glycol)s. The slopes of the Klotz binding plots appear to decrease in the lower picrate concentration range, suggesting that binding of the salt becomes more difficult at high picrate content. It was shown that under saturation conditions six to seven ethylene oxide units are required to bind a sodium picrate ion pair. The affinity of the PEO-resins for the alkali picrate can be enhanced by immobilizing a poly(crown ether) in the network. A number of competition experiments for sodium picrate in toluene was also carried out to obtain the affinity of soluble ligands for alkali salts. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1819-1824, 1997
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Radiopaque epoxy resins (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 851-856 
    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: Transparent, X-ray contrast (radiopaque) epoxy resins were obtained by dissolving up to 25 wt % triphenylbismuth in the commercial epoxy resin prepolymers EPON-815, DER-330, DER-383, and DEN-431 which were then hardened with diethylenetriamine. The radiopacities of the mixtures were found to be proportional to the molar concentration of the radiopaque additive. The systems follow the relationship, R = Ro + (Ra - Ro) Va Ma where R, Ro, and Ra are the radiopacities of the mixture, the pure epoxy resin, and triphenylbismuth, respectively (expressed in mm aluminum/mm resin); Ma and Va denote the molar concentration and molar volume of the bismuth compound. Ra for triphenylbismuth was found to be 7.4 ± 0.2 mm Al/mm resin; the average value of Ro for the four epoxies equals 0.16 ± 0.1 mm Al/mm resin. The amount of amine required to harden the radiopaque resins was far less for the epoxy novolac resin DEN-431 than for the three bisphenol-A based epoxies. The concentration of triphenylbismuth required to impart a radiopacity equivalent to that of aluminum measures 14.6 wt % in EPON-815, 14.8 wt % in DER-330, 14.9 wt % in DER-383, and 15.9 wt % in DEN-431. The radiopaque resins remain transparent indefinitely, even when exposed to water. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070550602
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  • 3
    Electronic Resource
    Electronic Resource
    Thermomechanical investigation of poly(methylmethacrylate) containing an organobismuth radiopacifying additive (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 31 (1996), S. 339-343 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previously we demonstrated the feasibility of using up to 24% triphenylbismuth (TPB) as a radiopaque, monomer-miscible additive for dental acrylic resins. In this study we examined the influence of TPB on thermomechanical properties of a representative polymethylmethacrylate (PMMA) ambient-cured resin used for temporary dental crowns and bridges. TPB (0%, 5%, 15% or 30% w/w) was dissolved in the monomer component, added to the powder component, and allowed to cure in rectangular molds. After 1 h they were either stored at 23°C for 23 h, or heated for 5 min at either 40°C or 50°C, and then stored for 23 h. They were then scanned from -10° to 125°C in a dynamic mechanical thermal analyzer using the three-point bending mode of deformation at 1-Hz frequency.The onset to the glass-transition temperature (Tg) is decreased by 13° to 32°C by addition of TPB, while the storage modulus (E′) at 25°C is either unchanged or is slightly increased. TPB did not interfere with the curing reaction, and postcure heating at 40°C had no effect on either E′ or Tg. However, heating at 50°C generally increased Tg but had very little effect on E′ throughout the 0-50°C operating temperature range. TPB crystals were observed to have precipitated at TPB levels above 8%. These crystals, dispersed throughout the PMMA, act as reinforcing fillers. This reinforcement can account for the lack of a decrease in E′, as would be expected if TPB had a plasticizing effect below Tg. However, even at 5%, a concentration at which all the TPB remains dissolved in the solid polymer, no decrease in E′ was observed. This implies that TPB exerts an antiplasticizing effect at temperatures below 50°C, possibly by occupying free volume among the polymer chains.It is concluded that TPB, in amounts adequate to impart diagnostic levels of radiopacity, is unlikely to adversely affect the clinical utility of PMMA-based dental acrylic resins. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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