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  • Polymer and Materials Science  (63)
  • Antisense repression  (1)
  • 11
    Digitale Medien
    Digitale Medien
    Measured and calculated solubility of polymers in mixed solvents: Co-nonsolvencyDedicated to Professor Dr. J. W. Breitenbach in honor of his 70th birthdayAfter submission of this paper Professor Dr. J. W. Breitenbach deceased on 6. 1. 1978. (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 2265-2277 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The phenomenon of co-nonsolvency, i.e. the formation of nonsolvents by mixing two solvents, was studied for the system N,N-dimethylformamide/cyclohexane/polystyrene (DMF/CH/PS) which is characterized by the fact that the components of the mixed solvent are only incompletely miscible below 48,6°C. A number of quasibinary sections (stepwise addition of the second solvent to given solutions of the polymer in the first solvent) for a sample (M = 110000) of high molecular uniformity yielded a cloud point surface which gives “island curves” (closed solubility gaps) for constant temperatures between the critical temperature of DMF/CH and the top of the cloud point surface (51,3°C). The attainment of equilibrium is facilitated by the addition of DMF to CH or solutions of PS in CH, as compared with the opposite procedure. By means of phase equilibrium experiments tie lines and the critical curve could also be constructed. For a theoretical calculation of the latter from information concerning the binary sub-systems (e.g. light scattering of PS in DMF) the single liquid approximation was applied to DMF/PS instead of - with respect to miscibility - the more dissimilar DMF/CH; the results are in qualitative accord with experimental observations. Orienting measurements concering the chain length dependence of the partition coefficient in co-nonsolvent systems indicate that their aptitude for fractionation is considerably worse than that of normal systems under comparable conditions.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1978.021790914
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  • 12
    Digitale Medien
    Digitale Medien
    Oligomer-oligomer incompatibility, 2Part 1: cf. ref.1. Oligo(dimethylsiloxane)/oligo(propylene glycol)Dedicated to Professor G. Meyerhoff on the occasion of his 60th birthday (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 2591-2603 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The demixing behavior of 20 representatives of the system oligo(dimethylsiloxane)/oligo(propylene glycol) (ODMS/OPG)The prefix “oligo” has been chosen for all products, since the addition or removal of a few monomeric units changes the physical properties considerably (cf. Tab. I), even in the case of the highest molecular weight sample. is investigated at pressures up to 1 500 bar. The degrees of oligomerization range from 2 to 5 for the first and from 1 to 57, 6 for the second component. The experimental results are compared with those for the previously studied system oligoisobutene/oligo(propylene glycol) (OIB/OPG). In both cases the observed upper critical temperatures Tc increase with the number of monomeric units of the less polar component, whereas they run through a minimum when the number of monomeric units of the glycol is raised. For the present system the Tc values are found to be considerably higher than that of OIB/OPG and the optimum compatibility can normally be observed already between 1 and 7 propylene glycol units as against 50 in the case of OIB/OPG. In the low pressure region Tc of ODMS/OPG is decreased by pressure for all representatives of this system, while enhanced incompatibility has been found with OIB/OPG. For ODMS/OPG the special features of the critical lines are determined by the chain length of OPG, for OIB/OPG by that of OIB. For ODMS/OPG the initial reduction of Tc by pressure is most pronounced with the highest molecular weight oligo(propylene glycol), for which it amounts up to 0,3 K/bar; with increasing pressure and decreasing chain length the effects become smaller. For the lowest molecular weight sample of OPG the critical lines show a vertex at 700-1000 bar. In any case the two systems under consideration behave in an increasingly similar manner as the pressure is raised. The theoretical evaluation and discussion of the above results is performed by analogy with that of the first paper in this series.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1979.021801104
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  • 13
    Digitale Medien
    Digitale Medien
    Continuous fractionation and solution properties of PVC, 3Part 1, 2: cf. 1,2. Pressure dependence of the solubility in single solventsIn memoriam of Professor G. Rehage (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 769-776 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: From the break-down in the viscosity and from the increase of the intensity of the scattered light, associated with the entrance into the two-phase region, the pressure dependence of the demixing temperature of solutions of PVC 37 000, PVC 75 000 and PVC 100 000 in phenetole and PVC 75 000 in o-xylene was measured up to 1 000 bar. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) The application of pressure increases the demixing temperatures of PVC in both solvents by about 1 K/100 bar. For a qualitative forecast of the pressure effects, the solubility parameter theory in combination with the corresponding states principle, and an empirical correlation to the relative distance of the critical demixing temperature to the melting point of the pure solvent were used. The results of both concepts are in accord with the experimental findings.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1985.021860409
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  • 14
    Digitale Medien
    Digitale Medien
    Continuous fractionation and solution properties of PVC, 4Part 1-3: cf. Refs.1-3. Pressure dependence of the solubility in a mixed solventDedicated to Professor K. J. Ivin in honour of his 60th birthday (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 777-785 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Using a self-constructed light scattering apparatus, the pressure dependence of the demixing temperature of solutions of PVC 20 000, PVC 37 000 and PVC 70 000 in THE/water was determined up to 1 000 bar for different compositions of the mixed solvent. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) In contrast to the thetasolvents o-xylene and phenetole, the solubility decreases with increasing pressure for all molecular weights and compositions under investigation typically by about 1 K/100 bar. The evaluation of the experimental findings demonstrates that the volume fraction of the nonsolvent in the mixed solvent, ϕ2*, is the variable that governs phase separation: For the present region of p and T, a given polymer solution demixes at a characteristic constant value of ϕ2*, no matter how it is reached. This fact allows the prediction of pressure influences from known pVT data of the pure components and measurements at atmospheric pressure. A qualitative theoretical understanding of the observed influences of p and T can be reached on the basis of the solubility parameter theory.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1985.021860410
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  • 15
    Digitale Medien
    Digitale Medien
    Continuous fractionation and solution properties of PVC, 5Part 1-4: cf. Refs.1-4. Pressure dependence of the viscosity  -  influence of solventDedicated to Professor J. Schurz in honour of his 60th birthday (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 787-799 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Viscosity measurements were carried out as a function of pressure and temperature with solutions of 8 wt.-% PVC (Mw ≈ 75 000) in ten thermodynamically good solvents by means of a Searle-type viscometer. A rollingxyhball viscometer was used for the investigation of the pure solvents. In all cases the viscosity increases in a more or less exponential manner when the pressure is raised. The viscosity ratio f1000 = η1000 bar/η1bar can be varied by the choice of the solvent from ca. 2 (tetrahydrofuran) to 3,0 (cyclohexanone) at 40°C. For a constant temperature of 40°C, the volumes of activation for the viscous flow of the solutions, V≠, or f1000 exceed that of the pure solvent, by typically 25%. The dependence of f1000 or V≠ upon temperature is not very pronounced. However, the greater the f1000-values, the more marked are the temperature effects. The theoretical analysis of the data, including earlier measurements with PS, indicates that three terms contribute to f1000: the basic value (f1000)s stemming from the pure solvent, the value (f1000)p which the polymer would contribute under athermal conditions, and finally a thermodynamic term, (f1000)pa, considering the pull-along effect (i.e. the specific forces a given segment exerts on other segments under variable thermodynamic conditions).
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1985.021860411
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  • 16
    Digitale Medien
    Digitale Medien
    Continuous fractionation and solution properties of PVC, 6Parts 1-5: cf. refs. 1-5. Pressure dependence of the viscosity  -  influence of molecular weight and compositionDedicated to Professor O. Fuchs in honour of his 80th birthday (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 801-815 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Viscosities were measured as a function of pressure and temperature with solutions of PVC 75 000 in cyclohexanone (CHO) and polymer contents ranging from 0,6 to 12 wt.-%, by means of a Searle-type (≥3 wt.-%) and a rolling-ball viscometer (〈3 wt.-%). Furthermore, the influence of molecular weight was determined with solutions of 8 wt.-% of PVC 20 000, PVC 37 000 and PVC 100 000. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) For all concentrations and molecular weights, the viscosity increases in a more or less exponential manner with increasing pressure. The ratio f1000 of the viscosity of the solution at 1 000 and 1 bar can be varied by the change of the polymer content from 2,5 (the value of the pure solvent, index s) to 3,5 (12 wt.-% PVC 75 000) at t = 25°C and from 2,23 to 2,94 at t = 80°C. An increase of the molecular weight of the polymer raises f1000 in a similar manner as the polymer concentration. Using the reduced variables V≠/V≠ (ratio of the volumes of activation of the solution and the pure solvent) and c̃ (product of the polymer concentration and the intrinsic viscosity), all results obtained by variation of T, c and Mw can be represented by a master curve. This means that it is possible to calculate the pressure dependence of a given polymer solution of arbitrary polymer concentration from a mere measurement of the intrinsic viscosity at normal pressure. Criteria are presented which allow a forecast concerning the occurrence of minima in the concentration dependence of the energy of activation of the viscous flow E≠ and V≠.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1985.021860412
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  • 17
    Digitale Medien
    Digitale Medien
    Thermodynamics and high-pressure viscosity of dilute solutions of poly(decyl methacrylate) and how the free volume influences themAffectionately dedicated to Prof. H.-J. Cantow on the occasion of his 65th birthday (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 2067-2075 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Light scattering and viscometric measurements were performed for the system isooctane/poly(decyl methacrylate) of weight-average molecular weight M̄w = 250 000 within the concentration regime of pair interaction between the macromolecules in the temperature range from 25°C to 100°C. In case of the intrinsic viscosities [η], the pressure was varied up to 3500 bar. Under isobaric conditions, the osmotic second virial coefficients A2, the z-average radii of gyration rz and [η] pass through a maximum, the Huggins coefficient kH through a minimum, with variation of temperature. These extrema indicate a change in the heat of dilution from endothermal at low, to exothermal at high temperature T. The calculation of the temperature dependence of the intrinsic viscosity [η] (T) for isochoric conditions does not yield a maximum, provided the pressure at the lowest temperature is chosen close to atmospheric pressure; it can, therefore, be concluded that the change in the sign of the enthalpy is in this case only due to the free volume of the system which increases markedly with increasing T. For pressures larger than ≈700 bar, maxima are always observed, no matter whether the temperature is changed isobarically or isochorically. All parameters under investigation are closely interdependent: A one-to-one correspondence exists between [η] and A2 at 1 bar, and kH and [η] interrelate linearly for constant T.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1988.021890909
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  • 18
    Digitale Medien
    Digitale Medien
    Vapour pressures of the system tert-butyl acetate/polystyrene (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 2161-2167 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An apparatus is presented for the precise measurement of vapour pressures. It is tested with diethyl ether and applied to the system tert-butyle acetate/polystyrene (weight-average molecular weight Mw = 110000) up to polymer concentrations of ca. 60 wt.-% in the temperature range from 10 to 90°C; by means of the Redlich-Kister equation the results can well be described analytically. The data are evaluated to yield the Flory-Huggins parameter in the subsequent article in conjunction with other experimental information.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1984.021851011
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  • 19
    Digitale Medien
    Digitale Medien
    Continuous fractionation and solution properties of PVC, 1. Continuous fractionation, characterisationDedicated to Professor R. Koningsveld in honour of his 60th birthday (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 735-751 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A new Continuous Polymer Fractionation method, called CPF, is described. The polymer to be fractionated is dissolved in a solvent/non-solvent mixture, and this solution (feed) is extracted continuously by a second liquid (extracting agent), which contains the same solvent components as the feed. In the case of PVC, the fractionation was carried out with a pulsed counter current extraction apparatus and THF/water was used as solvent/non-solvent mixture. Fractionation is achieved by the fact that the molecules are distributed over the counter current phases according to their chain length; the feed leaves the column as gel and the extracting agent as sol. First some explorative experiments were made in order to determine suitable working parameters, like frequency and amplitude of pulsation, compositions of feed and extracting agent and the ratio of flow. With the so obtained parameters, preparative experiments were carried out, yielding five PVC-fractions with molecular weights ranging from 20 000 to 100 000 (GPC, LS) and non-uniformities, U = (Mw/Mn) -1, of about 0,2 (GPC) using a starting material with Mw = 67 000 and U = 0,95.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1985.021860407
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  • 20
    Digitale Medien
    Digitale Medien
    Continuous fractionation and solution properties of PVC, 2Part 1: cf. 1. Scrutiny of solvents, intrinsic viscosityDedicated to Professor H. Inagaki in honour of his 60th birthday (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 753-767 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Investigations with ca. 100 organic liquids in a temperature range from -20°C to 90°C result in a survey of the solubility behaviour of PVC. The experimental results were compared with the predictions of the solubility parameter theory: Accepting δ = 9,75 (cal/cm3)1/2 as the solubility parameter for PVC, all solvents (except ketones in which PVC is soluble independent of their solubility parameters) are located within the range of δPVC ± 0,75. Only three of the 100 liquids examined turned out to be (endothermal) theta-solvents, namely the aromatic solvents o-xylene, phenetole and dimethyl phthalate. The theta-temperatures in o-xylene and phenetole were determined viscometrically by means of the temperature dependence of the Mark-Houwink exponent to be 84 and 88°C, respectively. Viscosity measurements were also performed in the temperature range of 25 to 60°C with solutions of PVC 75 000 in 10 thermodynamically good solvents used for rheological investigations. In all cases the intrinsic viscosities decrease slightly with increasing temperature, i.e., all solutions are weakly exothermal. The binary cluster integral, β, was determined (taking the monomeric unit as the statistical segment) and the polar contribution, βe, was calculated from Yamakawa's theory. The correlations between the non-polar part of (βn = β - βe) and the solubility parameter of the solvent, found by Utracki, were tested and found to be valid for the present systems, too.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1985.021860408
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