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  • 1
    Electronic Resource
    Electronic Resource
    Consistent values of rate parameters in free radical polymerization systems. II. Outstanding dilemmas and recommendations (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 851-863 
    Details
    ISSN: 0887-624X
    Keywords: polymerization ; kinetics ; free radical ; transfer ; photolysis ; propagation ; rate coefficients ; termination ; EPR ; copolymerization ; initiation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problems of determining reliable, well-characterized values of kinetic parameters in free-radical polymerizations are discussed. The origins of the fact that experimental determinations of rate coefficients of ostensibly identical systems often result in quite different values being reported can be ascribed to subtle mechanistic assumptions made in data interpretation, which are considered in detail. A series of recommendations to assist in overcoming these problems, and to highlight their origins, are presented, with emphasis placed on new techniques including those employing laser photolysis and EPR.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300516
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  • 2
    Electronic Resource
    Electronic Resource
    Rheokinetics of polymerization of N-laurylmethacrylate (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 402-409 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The free radical polymerization of n-laurylmethacrylate has been studied using a combination of rheological and kinetic methods. In addition to classical dilatometry, the extent of reaction of a polymerization was followed in a cone and plate rheometer by measuring the change in the diffraction of a laser beam shone through the polymerizing sample parallel to the plate of the rheometer. The change in diffraction was caused by the change in index of refraction of the monomer becoming polymer, which was related to the extent of reaction. Simultaneous measurements of loss and storage moduli and dynamic viscosity at 1 Hz provided the data necessary for correlating changes in the kinetics with changes in the rheology of the polymerizing system.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760220703
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of ultrasound on free-radical polymerization in a continuous stirred tank reactor (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 1111-1117 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl methacrylate has been continuously polymerized in toluene solution with AIBN as an initiator at 60°C in a jacketed steel vessel of 890 ml volume with holding times of several hours. Provision was made for good mixing and introduction of a steady stream of monomer, solvent, and initiator. The effluent stream was analyzed for polymer content and molecular weight distribution by gel-permeation chromatography. After the reactor had been operating for three holding times, an ultrasonic probe in the reactor was turned on, and the effect of the ultrasound on the steady-state operation of the reactor was observed. The ultrasound caused a rapid increase in the conversion level. A small, concomitant increase in the degree of polymerization was also noted. It is proposed that the ultrasound breaks polymer chains, giving polymeric free radicals which increase in size while increasing the rate of polymerization. Simulation of the polymerization in the stirred tank reactor has been achieved by using a digital computer, and a quantitative treatment of the effect of ultrasound has been developed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.170110517
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  • 4
    Electronic Resource
    Electronic Resource
    Spatially intermittent polymerization (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 14 (1976), S. 869-881 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel reactor has been designed which permits the precise determination of absolute rate constants in photoinitiated free-radical vinyl polymerization. A solution of monomer and initiator flows through a dark tubular reactor past regularly spaced slots through which light shines. The alternating dark and light regions produce spatially intermittent polymerization (SIP) and make the system analogous to the well-known rotating-sector technique. However, the SIP reactor has the advantage of producing large volumes of reaction product, at low conversion, suitable for analysis of both conversion and molecular weight. This supplies the necessary data, from a single set of experiments, for the simultaneous determination of the rate constants for propagation and termination. Experimental data are reported at 25°C for methyl methacrylate which indicate that kp = 315 I./mole-sec, independent of polymer molecular weight, and kt is dependent on molecular weight especially at low molecular weight, approaching a lower value of kt = 30 × 106 I./mole-sec at a molecular weight of 106. For styrene, measurements being made only at high molecular weight, kp = 74 ± 5 and kt = 37 ± 0.3 × 106 l./mole-sec at 25°C.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.170140408
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  • 5
    Electronic Resource
    Electronic Resource
    Termination rate constant in free-radical polymerizationPart II of a series on absolute rate constants in free-radical polymerization. For Part I, see O'Driscoll and Mahabadi.1 (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 283-300 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The specific rate constant for the termination reaction between two flexible polymer molecules with active chain ends has been considered in relation to the segmental diffusion of chain ends in solution. The probability of reaction between two chain ends per unit time when the centers of gravity of two polymer molecules are at a distance of separation has been calculated by using the Smoluchowski equation and a Gaussian distribution of chain ends. The time during which two polymer molecules are in contact has also been calculated by using the diffusion equation and the potential energy function for intermolecular interaction. The rate constant may then be completely expressed as a complex function of the intramolecular linear expansion factor, molecular weight, and the frictional properties of the reacting polymers' segment. This expression predicts that the rate constant is inversely proportional to solvent viscosity, decreasing with increasing molecular weight to some extent, and is affected by the excluded volume effect and chain flexibility. The complete expression for the rate constant has been simplified and the result compared with experimental data. Close agreement is found between the calculated rate constants and those experimentally obtained.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170150203
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  • 6
    Electronic Resource
    Electronic Resource
    The termination reaction in free radical copolymerization. I. Methyl methacrylate and butyl- or dodecyl methacrylate (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 3913-3921 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a spatially intermittent reactor, the absolute rate constant for the termination reaction in free radical copolymerization has been measured for the monomer pair methyl methacrylate (MMA)-butyl methacrylate (BMA). For the pair MMA-dodecyl methacrylate (DMA) the relative rate constant for termination has been measured. In both cases the termination rate constant was a monotonically changing function of the monomer feed composition. This function can be well approximated by a simple calculation of the enchained monomer units' contributions to the average segmental friction coefficient of the copolymer chain. An attempt to apply a previously derived theoretical treatment based on penultimate unit effects produced physically unrealistic results.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170171211
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  • 7
    Electronic Resource
    Electronic Resource
    The use of the error-in-variables model in terpolymerization (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 2003-2010 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The error-in-variables model (EVM) is a mathematical description of experiments in which there is error in all measured variables. This contrasts with ordinary least-squares methods in which it is assumed that error is only present in the dependent variable or variables. EVM leads to statistical procedures which are able to obtain more efficient estimates of unknown parameters from data with error in all the variables than can be obtained by using least-squares methods. One type of experiment to which EVM is applicable is the measurement of copolymer reactivity ratios. It has been applied recently to the binary case, but the only known method for estimating reactivity ratios in ternary systems is that of Rudin et al. which is based on ordinary least squares. The application of EVM to the problem is described in this article and the results are compared with those of Rudin et al.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.170210711
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  • 8
    Electronic Resource
    Electronic Resource
    Applicability of the Mayo-Lewis equation to high conversion copolymerization of styrene and methylmethacrylate (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 2777-2788 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In contradiction to reports from this and other laboratories, this study reports that the integrated Mayo-Lewis equation, or Meyer-Lowery equation, adequately describes the high-conversion free radical copolymerization of styrene and methylmethacrylate. The copolymerization was monitored by following the changes in the feed composition using NMR, as well as determination of the resulting copolymer compositions by NMR and UV. “Error in all Variables” statistical techniques were used to produce estimates of the reactivity ratios. The reactivity ratios estimated were, from feed composition, NMR, r1 (styrene) = 0.472, r2 = 0.454, from copolymer composition, UV, r1 = 0.497, r2 = 0.464, and NMR, r1 = 0.432, r2 = 0.422.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.170221104
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  • 9
    Electronic Resource
    Electronic Resource
    High-conversion polymerization. VII. A definition of the explosive region and the influence of free volume on itFor Part VI see ref. 1. (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 3199-3209 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The easily observed autoacceleration of free radical Polymerization is defined as the explosive region and an arbitrary but quantitative definition of it is made. Using this definition it is shown that the explosive regions of solution polymerizations of methyl methacrylate occur at constant values of the product of polymer concentration times (molecular weight)1/2. This upholds the concept that polymer entanglements control the termination reaction in this region. It is also shown that this region does not, as previously suggested, occur at a constant value of free volume, but that free volume does play a role in determining the rate of termination at a given level of chain entanglements.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170181106
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  • 10
    Electronic Resource
    Electronic Resource
    High-conversion polymerization. I. Theory and application to methyl methacrylate (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 14 (1976), S. 883-897 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concept of polymer entanglements has been applied in conjunction with classical free-radical kinetics to describe vinyl polymerizations carried to high conversion. A kinetic model has been developed on the assumption that two populations of radicals exist in a high-conversion polymerization system: those radicals whose chain lengths are long enough to become entangled with neighboring molecules and have, therefore, a restricted mobility; and those shorter radicals whose mobilities are not strongly affected by diffusional effects. It has also been assumed that the kinetic rate constant for the termination step between entangled radicals is inversely proportional to the mean entanglement density. The model contains only two parameters in addition to the kinetic rate constants required to describe low-conversion polymerizations. One of these parameters can be determined, at least in principle, from measurements of solution properties of the polymer-monomer mixtures. The model so developed has been tested against experimental data obtained from the literature on the bulk polymerization of methyl methacrylate. The agreement between predicted and experimental monomer conversions and molecular weight averages is found to be satisfactory.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.170140409
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