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  • 1
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 779-785 
    ISSN: 0899-0042
    Schlagwort(e): optically active oxiranes ; liquid crystals ; epichlorohydrin ; glycidol ; chiral HPLC ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of racemic and optically active oxiranes, bearing mesogenic groups, precursors of liquid crystalline polyethers, has been synthesized from epichlorohydrin or glycidol. The enantiomeric excess of the optically active oxiranes has been determined by chiral stationary phase HPLC. Compounds bearing 4-cyanobiphenyl mesogenic group exhibit monotropic liquid crystalline behavior. A transfer of chirality to the mesophase has been observed for the optically active oxiranes, which present a cholesteric phase. Chirality 10:779-785, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 139-148 
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Racemic and optically active protected glycidols (as 1-ethoxyethyl ethers) are readily polymerized with anionic initiators (e.g., CsOH). Polymers with molecular weights up to 30 000 are obtained without cleavage of the protective group. Oligomers (degree of polymerization [DPn] 5 to 10) are prepared using an aluminium complex derived from a Schiff's base. The protected thioglycidol (synthesized from the protected glycidol) leads to very high-molecular-weight polymers (150 000-320 000) using anionic or anionic coordinated initiators. Copolymers of protected glycidol with ethylene oxide are obtained with KOH as initiator. Regeneration of hydroxyl groups in polymers is carried out with acidic cleavage. Treatment of protected polyglycidol with formic acid leads first to the formate of polyglycidol. Then, after saponification, pure polyglycidol is obtained. The use of aqueous hydrochloric acid leads directly to the free polymer.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Oxiranes bearing a 4-cyanobiphenyl-4′-oxy mesogenic group with spacers of different length have been synthesized from glycidyl p-toluenesulfonate or epichlorohydrin (racemic or optically active). These monomers were polymerized with anionic initiators (CsOH, tBuOKtBu: tert-butyl, Et: ethyl.) or a chelate initiator (AlEt3/H2O/acetylacetone). A transfer of chirality from the polymer backbone to the mesophase is observed for polyethers with a short spacer. A cholesteric phase is observed for the optically active polymer while the racemic polymer is nematic. Increasing the length of the spacer leads to a smectic mesophase. However, in that case, the effect of the chiral centre of the polymer backbone on the mesomorphous properties is not detected.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 5 (1994), S. 203-215 
    ISSN: 1042-7147
    Schlagwort(e): Liquid crystalline polymers ; Polyethers ; Chirality ; Cholesteric polymers ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Racemic and chiral [(4-cyano-4′-biphenyl)oxy] and [(4-methoxy-4′-biphenyl)oxy]methyloxiranes were prepared from racemic epichlorohydrin or racemic and chiral glycidols and polymerized in dimethylsulfoxide (DMSO) with ButOK as the initiator system. Initial phase identifications were made by differential scanning calorimetry (DSC) and optical microscopy techniques and confirmed by X-ray diffraction measurements. Upon heating, all the monomers show only a crystal-isotropic phase transition. The racemic and chiral [(4-cyano-4′-biphenyl)oxy]methyloxiranes exhibit a nematic and a cholesteric monotropic phase, respectively. Methoxybiphenyl substituted polyethers are crystalline and insoluble in virtually all common solvents. Cyanobiphenyl substituted polyethers are soluble under the same experimental conditions and show enantiotropic liquid crystalline properties. The racemic polymer exhibits a nematic phase, while the optically active polymer forms a cholesteric phase.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2501-2510 
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Newly designed polystyrene (PS)/poly(ethylene oxide) (PEO) branched copolymers were obtained by a sequence of reactions involving both cationic and anionic polymerizations. Stars made of six PS-b-PEO arms and PS/PEO copolymers constituted of an inner PS part and an arborescent outer layer of PEO are two novel amphiphilic branched architectures that are described in this paper. The investigation of the solution properties of these copolymers by size exclusion chromatography (SEC) using tetrahydrofuran and an aqueous medium revealed that PS/PEO arborescent copolymers are more inclined to self-organize into unimicellar systems than their star homologues.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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