Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Effect of pressure on free-radical copolymerization kinetics. I. A concept of additivity of partial molar volumes of activation (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 1765-1772 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A short review of the effect of pressure on copolymerization kinetics shows the necessity of simple models for a better understanding of activation volumes. Therefore, a simple concept, possibly generally valid for free-radical polymerization, is proposed, based on the assumption that molar volumes of activation can be expressed as an addition of a characteristic radical and a monomer contribution, regardless of the combination involved. The scheme may facilitate the visualization of the transition state and contribute to the understanding of reaction mechanisms of radical polymerizations. Ethylene-vinyl acetate copolymerization at 62°C with tert-butyl alcohol as solvent agrees with the proposed scheme, appearing from the pressure independence of the product of reactivity ratios at the different levels (35,600, and 1200 kg/cm2). Implicitly it can be shown that an ethylene monomer contributes about 2 cm3/mole more to the activation volumes of the propagation reactions than does the vinyl acetate monomer, whereas for the radicals the difference of the respective contributions to the activation volumes is opposite in sign.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170150724
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Improved methods of estimating monomer reactivity ratios in copolymerization by considering experimental errors in both variables (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 2915-2930 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Existing methods of calculating monomer reactivity ratios in copolymerization are reviewed briefly, evaluated, and classified according to their mathematical and computational similarities. More attention is paid to procedures based on the integrated copolymer equation with which calculation of r values is performed most often by electronic computer. Unfortunately, until now all procedures have shown shortcomings because the real-error structure of the observations has not been taken into account. A new algorithm that does account correctly for measurement errors in both variables is described. A computational method is illustrated for copolymerization data obtained from quantitative gas chromatographic analysis of the monomer feed throughout the reaction. It is shown that the actual error structure of the variables corresponds to the assumed error structure. Reliability of the estimates is substantially increased, compared with the existing methods. Standard deviations of the monomer reactivity ratios are given and appear to be in good agreement with reality.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.170161117
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Effect of pressure on free radical copolymerization kinetics. II. Novel methods of measuring monomer reactivity ratios under high-pressure conditions (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 571-582 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new techniques for the determination of monomer reactivity ratios in copolymerization under high-pressure conditions have been developed, viz., the “sandwich” and the “quenching” method. Both methods are based on repeated quantitative gas chromatographic analysis of the reaction mixture during the low-pressure stages preceding and succeeding the high-pressure stage, of which the kinetics is under investigation. Application of the “sandwich” method implies the occurrence of reaction during both low-pressure stages and consequently the low-pressure kinetic data are required to obtain the transition points of low to high pressure and vice versa. These points constitute the initial and final conditions of the relevant high-pressure reaction. On the contrary, in the “quenching” method no reaction occurs during the low-pressure stages, owing to the lower temperature and the high activation energy of the initiator decomposition. As a consequence, the initial and final conditions of the high-pressure stage can be determined by a simple averaging procedure. Both methods have been tested for the ethylene - vinyl acetate copolymerization at 62°C and 600 kg/cm2 with tert-butyl alcohol as solvent, and appear to lead to almost identical monomer reactivity ratios, although the “quenching” method is slightly preferred in case of copolymerization reactions. Both methods are particularly valuable when one of the reactants is gaseous or the reaction produces a gas. Further merits and drawbacks of both methods are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170226
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Evaluation of monomer reactivity ratios of more complex copolymerization schemes, with application to the penultimate unit effect in methyl acrylate-butadiene copolymerization (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 3349-3364 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A generally applicable computational procedure, which permits the accurate evaluation of the kinetic parameters of intricate and extended copolymerization schemes to be made, is described. This method is based on a numerical integration of the differential equation, and, according to the (improved) curve-fitting I procedure, experimental errors in both measured variables are considered. Furthermore, a description is given of the F test, in which a statistical comparison between the resulting residual sums of squares of two different schemes offers a possibility of selecting the most probable kinetic scheme for a given copolymerization system. The capability and applicability of the methods developed is demonstrated for the free radical copolymerization kinetics of methyl acrylate (MA) (M1) and butadiene (BD) (M2) with toluene as solvent. Here, the simple copolymer equation is unsatisfactory because a significant penultimate unit effect in BD macroradical reactivity shows up: k222/k221 = 0.84, and k122/k121 = 0.53, and k11/k12 = 0.088. The microstructure of the copolymer samples, determined by infrared (IR) spectroscopy, shows a decreasing fraction of BD units in the vinyl configuration in favor of the fraction of BD units in the cis-vinylene and trans-vinylene configuration at increasing MA (m) content. Statistical considerations indicate a strongly diminished probability of finding BD (b) in the vinyl configuration in ∼mb∼ transitions. Steric hindrance or polar repulsion of the ester side group of the penultimate MA unit probably account for the increased preference for monomer addition to the C4 site over the C2 site of the BD macroradical.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170171024
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Copolymerization of vinyl acetate with a homologous series of vinyl esters: A comparative study of vinyl acetate-vinyl ester and ethylene-vinyl ester copolymerization (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 3365-3373 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the alkyl group on the relative reactivity of a homologous series of vinyl esters (M2) has been studied with vinyl acetate (M1) as reference monomer and tert-butyl alcohol as solvent at 62°C and 35 kg/cm2. The description of the relative reactivities of the vinyl esters toward the vinyl acetate (VAc) macroradical in terms of the Taft relation is analogous to our previous findings in a similar study with ethylene (Eth) as reference radical. This implies that chiefly polar factors affect the relative reactivity, whereas from vinyl pivalate (VPV) on steric hindrance impairs the addition rate. The constancy of the r2 values, also found in the series with Eth (M1) as reference monomer (viz., r2 = 1.50), appears to exist in the present investigation (r2 = 1.04) but does not hold for the VAc-VPV combination. This can be interpreted in terms of steric hindrance. A combination of kinetic results indicates sterically hindered additions in all those reactions in the system Eth-VAc-VPV that involve at least one VPV unit as macroradical or monomer (except for the addition of Eth to a VPV macroradical). The monomer reactivity ratios that pertain to the Eth-VAc-vinyl ester systems are discussed in terms of the Q-e scheme and the product relation postulated by Ham. The Ham relation does not hold for the latter systems.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170171025
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Effect of solvent on the copolymerization of ethylene and vinyl acetate (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 1347-1357 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ethylene (M1)-vinyl acetate (M2) copolymerization at 62°C and 35 kg/cm2 with α,α′-azo-bisisobutyronitrile as initiator has been studied in four different solvents, viz., tert-butyl alcohol, isopropyl alcohol, benzene, and N,N-dimethylformamide. The experimental method used was based on frequent measurement of the composition of the reaction mixture throughout the copolymerization reaction by means of quantitative gas chromatographic analysis. Highly accurate monomer reactivity ratios have been calculated by means of the curve-fitting I procedure. The observed dependence of the r values on the nature of the solvent is surprisingly large and can be correlated with the volume changes (= excess volumes) observed on mixing vinyl acetate (VAc) with the relevant solvent. An increased hydrogen bonding or dipole-dipole interaction through the carbonyl moiety of the acetate side group of VAc, induces a decreased electron density on the vinyl group of VAc, which in turn leads to a decreased VAc reactivity. The differences among the overall rates of copolymerization in the various solvents can be interpreted in terms of a variable chain transfer to solvent and the rate of the subsequent reinitiation by the solvent radical. In the case of benzene, complex formation is believed to play an important part.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180418
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Evaluation of monomer reactivity ratios of more complex copolymerization schemes, with application to the penultimate unit effect in methyl acrylate-butadiene copolymerization (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 1431-1431 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180426
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Structure-reactivity relations of conjugated and unconjugated monomers: Acrylates and methyl vinyl ketone in copolymerization with styrene compared with vinyl esters in copolymerization with ethylene (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 341-352 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article describes the copolymerization of methyl vinyl ketone (MVK), methyl acrylate (MA), and methyl methacrylate (MMA) with styrene (St) as reference monomer at 3.4 MPa and 335 K with toluene as solvent. In addition, the effect of pressure on the binary copolymerizations of St-Ma-MMA is discussed. It appearsthat in case of conjugated monomers reactivity decreases as the electron-donating character of the substituents increases, whereas the reverse is found in unconjugated monomers. This is explained by the finding that in conjugated monomers resonance effects induced by polar factors play a dominant role, whereas in unconjugated monomers mainly polar factors are governing the relative reactivities. The r values at 3.4 MPa are compared with those predicted by means of the Q-e scheme and Patterns. No definite conclusions could be drawn about the applicability and validity of either scheme, although Patterns shows excellent result in case of the H function of Mayo. In vinyl ester copolymerizations and Le Noble and Asano's example of the menshutkin reaction one single factor (polarity and steric hindrance, successively) dominates ΔG#, ΔG and ΔV#. This allows a straight forward interpretation of the result with the Hammond postulate and is in full agreement with Evan's potential-energy calculations. In conjugated monomers, however, an interplay of reasonance and polar factors is found. The general validity of these findings needs further experimental and theoretical support.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.170210204
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Copolymers of vinylamine and vinylalcohol by acid hydrolysis of poly(N-vinyl-tert-butylcarbamate-co-vinylacetate): Evaluation of reactivity ratios (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 2353-2362 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copolymers of vinylamine and vinylalcohol were prepared by hydrolysis of poly(N-vinyltert-butylcarbamate-co-vinylacetate) in 1:1 v/v % ethanol/HCl mixtures at room temperature. Reactivity ratios of the monomers N-vinyl-tert-butylcarbamate (1) and vinylacetate (2) were calculated from monomer feed and copolymer composition data, according to the methods of Fineman-Ross and Kelen-Tüdös, yielding r1 = 1.14 ± 0.05, r2 = 0.47 ± 0.07, and r1 = 1.12 ± 0.07, r2 = 0.46 ± 0.03, respectively. From these values the average sequence length distribution of monomer units was derived showing that in the raction of N-vinyl-tert-butyl carbamate and vinylacetate nearly Bernouillian (i.e., purely random) copolymers are formed, with a slight tendency toward alternation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.170221006
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Effect of pressure on free-radical copolymerization kinetics. III. An improved method of measuring monomer reactivity ratios under high-pressure conditions (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 2693-2703 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To investigate high-pressure copolymerizations a sampling technique has been developed enabling continual on-line GLC analysis of the reaction mixture. As a result more reliable kinetic data are obtained. This new “sequential sampling” method, allowing the use of gaseous monomers, has been tested for the copolymerization of ethylene with vinyl propionate at 118 MPa and 335 K with tert-butyl alcohol as solvent. The results are compared with those obtained with the “quenching” method used so far, which yields compositional data on the reaction mixture before and after the high-pressure stage, only. It is shown that the “sequential sampling” method is the most adequate method of determining high-pressure monomer reactivity ratios. Furthermore, it is an important safety feature that the present procedure can be easily remote controlled. The present experimental method is neither restricted to copolymerization nor to gas-chromatographic analysis of the reaction mixture.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.170200927
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...