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  • Chemistry  (79)
  • 2000-2004
  • 1990-1994  (39)
  • 1985-1989  (40)
  • 1
    Electronic Resource
    Electronic Resource
    Interaction of amphiphilic polymers with model membranes (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 166 (1989), S. 71-80 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The lipid bilayers of cell membranes are usually connected to two types of biopolymers: the cytoskeleton and the glycocalix. These structures are not only responsible for the stabilization of the lipid bilayer, they also alter the surface properties of the cells. Among the various attempts to mimick membrane properties using polymeric systems(1), one method is the fixation of amphiphilic polymers via hydrophobic anchor groups to lipid bilayers. In the experiments reported here the influence of amphiphilic polymers on the morphology of giant unilamellar liposomes has been investigated. Therefore a series of amphiphilic polyvinylpyrrolidone and dextran derivatives has been synthesized. The fixation of these polymers to the liposomal membranes could be shown with a fluorescence-labelled derivative by using epifluorescence microscopy. The polymer-membrane interaction caused by the insertion of the anchor groups leads to drastic morphological changes in this model membrane system. The exclusive interaction with the outer membrane of multilamellar liposomes could be demonstrated by freeze fracture electron microscopy. In addition, the anchoring of a natural capsular polysaccharide in liposomes has been proven by immunofluorescence. In these experiments, also a clustering (patching) of the antigen caused by the binding of the antibody could be observed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051660105
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of a Fullerene Derivative of Benzo[18]crown-6 by Diels-Alder Reaction: Complexation Ability, Amphiphilic Properties, and X-Ray Crystal Structure of a Dimethoxy-1,9-(methano[1,2]benzenomethano)fullerene[60] Benzene Clathrate (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 2445-2453 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fullerene derivative 1 of benzo[18]crown-6 was obtained by Diels-Alder addition of fullerene[60](C60) to the ortho-quinodimethane prepared in situ from 4,5-bis(bromomethyl)benzo[18]crown-6 (3) with Bu4NI in toluene. Extraction experiments show that the complexation of K+ ions strongly increases the solubility of 1 in protic solvents like MeOH. Using Langmuir-Blodgett techniques, monolayers of the highly amphiphilic fullerene-derived crown ether 1 and its K+ ion complex were prepared. An X-ray crystal structure was obtained from a benzene clathrate of comparison compound 2, synthesized by Diels-Alder reaction of C60 with the ortho-quinodimethane derived from 1,2-bis(bromomethyl)-4,5-dimethoxybenzene (4). Both the fullerene molecule 2 and the benzene molecule are fully ordered in a crystal packing which is stabilized by intermolecular van-der-Waals contacts between the benzene ring and the C-spheres, intermolecular C…C contacts between the C60 moieties, and intermolecular O…C contacts between the O-atoms of the veratrole moieties and fullerene C-atoms.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760704
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  • 3
    Electronic Resource
    Electronic Resource
    Photodimerization and photopolymerization of amphiphilic cinnamic acid derivatives in oriented monolayers, vesicles and solution (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 1843-1853 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cinnamic acid moieties were incorporated into amphiphilic compounds containing one and two alkyl chains. These lipid-like compounds with photoreactive units undergo self-organization to form monolayers at the gas-water interface and bilayer structures (vesicles) in aqueous solutions. The photoreaction of the cinnamic acid moiety induced by 254 nm UV light was investigated in the crystalline state, in monolayers, in vesicles and in solution in organic solvents. The single-chain amphiphiles undergo dimerization to yield photoproducts with twice the molecular weight of the corresponding monomers in organized systems. The photoreaction of amphiphiles containing two cinnamic acid groups occurs via two mechanisms: The intramolecular dimerization produces bicycles, with retention of the molecular weight of the corresponding monomer. The intermolecular reaction leads to oligomeric and polymeric photoproducts. In contrast to the single-chain amphiphiles, photodimerization processes of lipoids containing two cinnamic acid moieties also occur in solution in organic solvents.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1986.021870804
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric properties of a combined main-chain/side-chain liquid-crystalline polymer (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 1501-1509 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric relaxation properties of a combined main-chain/side-chain liquid-crystalline polymer were investigated. It was found that the rotation of the side chain about the main chain (δ-process) is not as strongly restricted as in side-chain liquid-crystalline polymers. This is attributed to the facts that the side chain is attached to the flexible spacer within the chain backbone and that the concentration of the side chains is comparatively small. Two low-temperature relaxation processes were observed to occur in the glassy smectic and the crystalline state. They are attributed to intramolecular motions with in the mesogenic groups.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021880624
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  • 5
    Electronic Resource
    Electronic Resource
    Preparation and characterization of unsymmetrical “liposomes in a net” (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 299-315 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Negatively charged lipid molecules were converted into polymerizable lipids by introduction of polymerizable mono- or bifunctional counterions. As an attempt to mimic the cytoskeleton of biomembranes, unsymmetrical polymeric vesicles were prepared, where the polyelectrolyte is attached either only to the inner or to the outer bilayer surfaces. Polymerizable cations were introduced to the outer surface of preformed small unilamellar vesicles via ion-exchange. The outer counterions of vesicles bearing polymerizable counterions at both sides of the membrane were replaced by Na+. Polymerization of these systems leads to unsymmetrical vesicles. The introduction, separation and polymerization of the organic counterions was monitored by UV-spectroscopy. Due to polymerization of the counterions, the phase transition temperature of the membranes is shifted remarkably to higher temperatures. For a comparison of ionically attached and covalently bound polymers, two cationic lipids were synthesized, which have a bifunctional polymerizable headgroup. In contrast to the lipids with “ionic” spacers, the polymerization of the covalently bound methacrylic units resulted in a decrease of the phase transition temperature. Thus, by application of ionically bound polymerizable units, unsymmetrical polymerized vesicle membranes are readily available. These systems may serve as models for mimicking the cytoskeleton of living cells.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890206
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  • 6
    Electronic Resource
    Electronic Resource
    Polyesters containing both rod-like and disc-like mesogens (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 507-513 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of a new type of combined polymers containing both disc- and rod-like mesogens is reported. The polyesters, having a triphenylene derivative as a discotic mesogen in the side group and azobenzene or biphenyl derivatives as rod-like mesogens in the main chain were characterized by polarizing microscopy, differential scanning calorimetry, and X-ray scattering studies. The homopolymer 7 is highly crystalline, while the copolymer 8 is amorphous, both, however, do not form liquid-crystalline phases.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930222
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  • 7
    Electronic Resource
    Electronic Resource
    Deuteron NMR study of molecular order and motion of the mesogenic side groups in liquid-crystalline polymers (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 2711-2723 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular order and mobility of two liquid-crystalline polyacrylates with phenyl benzoate moieties as mesogenic side groups and (CH2)m spacers (m = 2 and m = 6) were investigated by pulsed 2H NMR. The mesogenic side groups were isotopically labelled at the terminal phenylene ring. In the glassy state the orientational distribution function was characterized from the angular dependence of the 2H NMR line shape of samples macroscopically ordered in their nematic phase by the 8,4 T magnetic field of an NMR spectrometer. It was found to be Gaussian with widths of ± 18,5° and ± 10,5° for the m = 2 frozen nematic and m = 6 frozen smectic system, respectively. The phenylene rings undergo 180° jumps about their local C2-axes in the glassy state. The time-scale of this process, however, was found not to be uniform. Instead, the analysis of 2H NMR line shapes and their intensities as a function of temperature yielded a log-Gaussian distribution with correlation times characteristic of amorphous solids, 2,2 versus 2,5 decades in width and mean activation energy ĒA = 42 versus 47 kJ/mol for the m = 2 and m = 6 system, respectively. The correlation times for the centre of the distribution agree with those obtained by dielectric relaxation measurements of the same systems, suggesting that reorientation of the whole mesogenic group is detected via the phenylene rings.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1986.021871121
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis, structure, and phase behaviour of liquid-crystalline rigid-rod polyesters and polyamides with disc-like mesogens in the main chain (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 1431-1445 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Aromatic polyesters and polyamides with disc-like mesogens in the main chain were prepared from tetra-substituted hydroquinones and derivatives of 1,4-phenylenediamine. Depending on the atomatic acids (terephthalic acid, 2,5-dialkoxyterephthalic acid) used in the condensation reaction, the repeating units of these polymers carried 4 or 6 lateral substitutents. All polymers are highly soluble in several organic solvents, e.g. CHCl3, toluene, acetone. The phase behaviour of the polymers was studied by means of differential scanning calorimetry and optical polarizing microscopy. Depending on the number of lateral substitutents the polyesters and polyamides show crystalline and thermotropic liquid-crystalline phases. X-ray investigations showed a board-like Packing of the rigid-rod polymers which we have termed as a “sanidic” (meaning board-like) phase.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021880619
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal reactions of amphotropic copolymers studied by thermogravimetry and temperature-resolved pyrolysis-field ionization mass spectrometryDedicated to Prof. Dr. H. D. Beckey on the occasion of his 70th birthday (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1567-1587 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal degradation mechanisms of amphiphilic acrylic copolymers containing mesogenic pyrimidine side chains and hydrophilic 2-hydroxyethyl acrylate (HEA) main-chain spacer units were investigated by thermogravimetry (TG) and pyrolysis-field ionization mass spectrometry (Py-FIMS). The degradation behaviour of these polymers depends on the amount of HEA incorporated. Thermogravimetry revealed that the main decomposition occurs in a single step for the pyrimidine homopolymer, whereas with increasing HEA content a two-step process evolves. The major products identified by Py-FIMS are two alcohols and one olefin split from the aromatic side chains. Depolymerization is only a minor degradation pathway. The rather complex thermal behaviour can be explained by three different reaction mechanisms: (a) alcohol formation via reaction of the HEA hydroxyl groups with ester groups in the side chains, (b) intramolecular cis-elimination forming a volatile olefin and carboxylic acid groups remaining at the polymer backbone, and (c) the reaction of these acid groups with ester bonds forming the alcohols. Steps (b) and (c) are dominant for the pyrimidine homopolymer. With increasing HEA content in the copolymers step (a) becomes more important and, in addition, chemical crosslinking occurs. The mesogenic monomer, which was also examined, polymerized under the experimental conditions and showed essentially the thermal features of the pyrimidine homopolymer.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920711
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  • 10
    Electronic Resource
    Electronic Resource
    Conductivity and photoconductivity of undoped and doped Langmuir-Blodgett films of a polymer with hexaalkoxytriphenylene side-groups (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 2985-2999 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Langmuir-Blodgett films from a polymer with triphenylene moieties in the side groups deposited on a quartz substratum with aluminium and gold electrodes show a dark conductivity in the plane of the Langmuir-Blodgett film. This dark conductivity is increased using gold electrodes as compared with aluminium electrodes. It depends in a superlinear way upon the applied electric field and is not enhanced by oxygen. The dark conductivity can be enhanced by doping the Langmuir-Blodgett films with iodine but it is not influenced by doping the Langmuir-Blodgett films with 2,4,7-trinitro-9-fluorenone. Upon excitation in the absorption band of the triphenylene moiety an in-plane photocurrent, which is enhanced by oxygen, could be observed. Also the photocurrent is enhanced by using gold electrodes. Doping the Langmuir-Blodgett films with iodine or 2,4,7-trinitro-9-fluorenone quenches the photocurrent. Up to 10 W/m2 the photocurrent depends linearly upon the intensity of the incident light.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021941105
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