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  • 1
    ISSN: 0887-624X
    Keywords: poly(styrene-co-divinylbenzene) beads ; macroporous polymer ; monodisperse beads ; porous properties ; divinylbenzene content effect ; chromatographic evaluation ; high-performance liquid chromatography ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of concentration of divinylbenzene on pore size distribution and surface areas of micropores, mesopores, and macropores in uniformly sized porous poly(styrene-co-divinylbenzene) beads prepared in the presence of linear polystyrene as a component of the porogenic mixture has been studied. While the total specific surface area was clearly determined by the content of divinylbenzene, the sum of pore volumes for mesopores and macropores as well as their size distribution does not change within a broad range of DVB concentrations. Consequently, the size exclusion chromatography calibration curves are almost identical for all the beads prepared with different percentages of crosslinking monomer. However, the more crosslinked beads have better mechanical and hydrodynamic properties. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-6304
    Keywords: Water analysis ; polar pollutants ; solid-phase extraction ; chemically-modified polymeric resins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This study assesses how the physical characteristics of styrene-divinylbenzene (PS-DVB) resins affect the extent to which they are modified when they are functionalized, and how they affect recoveries in on-line solid-phase extraction (SPE) of some polar phenolic compounds, pesticides, and metabolites from water samples which were analyzed by liquid chromatography and UV detection. For this purpose, three commercial PS-DVB resins with different physical characteristics (Amberchrom GC-161m and two different PLRP-S resins) were chemically modified by placing a hydrophilic group, an o-carboxybenzoyl moiety, on their surface; although the physical characteristics are different, the extent of modification did not vary significantly. The results from the SPE process with each sorbent were related to their physical and chemical properties. The polymers with higher surface area provided better recoveries. Moreover, the recoveries for these analytes were better with the chemically-modified polymers due to the higher polarity of these sorbents. The best recovery values were with the sorbent obtained from the chemical modification of Amberchrom GC-161m, the commercial sorbent with higher surface area. For instance, in the analysis of 50 mL of a sample of 2 μg L-1, the recovery of phenol was 40% with Amberchrom GC-161m and 65% with the chemically-modified Amberchrom GC-161m.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Preparation and characterization of novel cycloaliphatic epoxy resins derived from tetrahydrophthalimide compounds were studied. Crosslinking studies on these resins were carried out using differential scanning calorimetry (DSC) and thermal gravimetry analysis (TGA). Thermal crosslinking overlaps with degradation and, therefore, hardeners or catalysts were used in order to decrease the crosslinking temperature. Primary or tertiary amines did not give curing reaction but the latter afforded isomerization to produce phthalimides when the amine was used in a great proportion. On the other hand, the use of anhydride (cis-1,2-cyclohexanedicarboxylic anhydride) as hardener and a tertiary amine (4-dimethylaminopyridine) as accelerator led to crosslinked materials. DSC was used to follow the reaction and a dynamic method was applied to obtain kinetic parameters. Thermal stability was evaluated by TGA.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several polymers were synthesized by reaction of unsymmetrical diacids with 4,4′-bis(2,3-epoxypropoxy)biphenyl. The reaction progress was followed, and the structure of the polyesters obtained was evaluated by means of 13C NMR spectroscopy. It appeared to be possible to achieve control in the polymer structure as a function of reactivity of the diacids. To obtain unequivocal assignments and to characterize thoroughly the NMR spectra of the polymers, several model compounds resembling the polymer backbone were synthesized.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of cycloaliphatic and glycidylic oxiranes with primary amines was examined; no reaction was observed for the former. From unsymmetrical cycloaliphatic glycidylic imide derivatives and primary amines, it was possible to obtain well defined epoxy-terminated biscycloaliphatic resins containing imide rings, which were identified by 13C NMR spectroscopy and elemental analysis. These epoxy resins were crosslinked by simple heating without hardeners and epoxide/amine-networks were obtained. The action of phthalic anhydride as curing agent gave different results depending on the nature of the starting cycloaliphatic group. Thus, while tetrahydrophthalimide derivatives, N-(2,3-epoxypropyl)perhydro-4,5-epoxyphthalimide (2), underwent crosslinking, nadimide derivatives, N-(2,3-epoxypropyl)-5,6-epoxybicyclo [2.2.1] heptane-2,3-dicarboximide (1) did not react. Differential scanning calorimetry was used to follow the reaction; in all the cases, only the dynamic method was applied, in order to obtain kinetic parameters. The values for activation energies are comparable to those reported for the curing of epoxide systems.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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