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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and phase-transfer catalytic activity of crown ethers bound to microporous polystyrene resins by oxyethylene spacers (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1089-1097 
    Details
    ISSN: 0887-624X
    Keywords: polymer-supported monoazacrown ethers ; phase-transfer catalysis ; spacer ; cooperative coordination ; complexation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Crown ethers bound to microporous polystyrene resins by oxyethylene spacers were prepared by the reaction of monoazacrown ethers with 2-tosyloxyethoxymethylated or 2-(2-tosyloxyethoxy)ethoxymethylated polystyrene resins crosslinked with 2 mol % of divinylbenzene. The activity of the immobilized lariat crowns for halogen exchange reactions under triphase conditions has been studied as a function of catalyst structure, loading, substrate structure, reagent structure, and solvent. The lariat catalysts with extra oxygen donors in the spacer chain exhibited higher activity than the corresponding immobilized catalysts without the donors in the spacer. The increased activity of the catalyst containing 15-crown-5 unit and two extra donors for the reaction of 1-bromooctane with KI was concluded to result from the enhanced complexation with the K+ ion, induced by the cooperative coordination of the crown unit donors and the donors in the spacer chain. The recovered catalysts could be re-used without decrease in activity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300615
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  • 2
    Electronic Resource
    Electronic Resource
    Toughening of aromatic diamine-cured epoxy resins by modification with hybrid modifiers composed of N-phenylmaleimide-styrene copolymers and N-phenylmaleimide-styrene-p-hydroxystyrene terpolymers (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 343-352 
    Details
    ISSN: 0959-8103
    Keywords: epoxy resin ; p,p′-diaminodiphenyl sulphone ; modification ; influence of hybrid modifier compositions ; fracture toughness ; 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: Hybrid modifiers composed of N-phenylmaleimide-styrene copolymers (PMS), and N-phenylmaleimide-styrene-p-hydroxystyrene terpolymers (PMSH) containing pendent p-hydroxyphenyl groups as functionalities, were used to improve the toughness of bisphenol-A diglycidyl ether epoxy resin cured with p,p′-diaminodiphenyl sulphone. The hybrid modifiers were effective in toughening the epoxy resin. When using the modifier composed of 10 wt% PMS (M̄w 313000) and 2.5 wt% PMSH (2.5 mol% p-hydroxystyrene units, M̄w 316000), the fracture toughness (KIC) for the modified resins increased 100% with no deterioration in the flexural properties and the glass transition temperature. The improvement in toughness of the epoxy resins was attained because of the co-continuous phase structure and the improvement in interfacial adhesion. The toughening mechanism is discussed in terms of the morphological characteristics of the modified epoxy resin systems.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210380405
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    Paper (German National Licenses)
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