Absolute propagation constants in vinyl polymerization

Bywater, S.

doi:10.1002/(sici)1099-0518(19991215)37:<4467::aid-pola1>3.0.co;2-b

Cited by 10 publications

(14 citation statements)

References 73 publications

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“…Once the 1 H NMR chemical shifts were assigned, HMQC connectivities readily afforded the corresponding carbon chemical shifts. The chemical shifts found were shown to be in good agreement with known literature values, , the determined chemical shifts were all within 2 ppm compared to the calculated values found for the cis and trans monomer units. Larger deviations were, however, found for the vinyl structure.…”

Section: Resultssupporting

confidence: 86%

Vulcanization of Butadiene Rubber by Means of Cyclic Disulfides. 2. A 2D Solid State HRMAS NMR Study on Cross-Link Structures in BR Vulcanizates

et al. 1999

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Vulcanizates of high cis-butadiene rubber (BR) obtained by using several cyclic disulfides such as 1,2-dithiacyclooctane, 1-oxa-4,5-dithiacycloheptane, and 2,3,12,13-tetrathia-[4,4]-metacyclophane, were studied by means of high-resolution magic angle spinning (HRMAS) solid state NMR spectroscopy in order to determine cross-linking sequence and overall molecular structure. DEPT-135 HRMAS spectra recorded at 60 °C provided the multiplicity of the different 13C resonances; interpretation of the HETCOR HRMAS spectra yielded the corresponding 1H frequencies. Direct and long-range through bond homonuclear connectivities were obtained from HRMAS COSY and TOCSY (total correlation spectroscopy) experiments. Comparison of these results with solution NMR data on hexyl disulfide grafted BR and previously described work on a cis,cis,cis-1,5,9-cyclododecatriene (ccc-1,5,9-CDT) based model system led to the elucidation of the entire network structures. The 13C chemical shifts found experimentally appeared to be in good agreement with chemical shifts calculated for the proposed structures. It was shown that cross-linking proceeds by means of addition of the cyclic disulfides to the carbon double bonds of BR instead of α substitution.

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Section: Resultssupporting

confidence: 86%

Vulcanization of Butadiene Rubber by Means of Cyclic Disulfides. 2. A 2D Solid State HRMAS NMR Study on Cross-Link Structures in BR Vulcanizates

et al. 1999

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“…All of the above‐mentioned results confirm the accuracy, precision, reliability, and robustness of the MLE method for kinetic parameter estimation in copolymerization systems, and the values of estimated kinetic parameters are in the permissible range of methacrylates in free‐radical polymerization (Bywater, 1999; Hutchinson et al, 1997). For all cases discussed above, convergence is stable and rapid.…”

Section: Resultssupporting

confidence: 60%

Reactivation of precore mutant hepatitis B virus in chemotherapy-treated patients

Dai

Chen

et al. 2001

Cancer

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A kinetic study of free‐radical solution copolymerization of isobutyl methacrylate and lauryl methacrylate in benzene, initiated with 2,2‐azoisobutyronitrile (AIBN) was performed at different monomer feed compositions, at low conversion level. To avoid the complications of copolymerization kinetics, the compositional‐averaged rate constant method was applied to dead‐end polymerization in constant and variable volume polymerization systems. A conditional probability approach, with “maximum likelihood function” (MLF), was used for estimating the kinetic parameters from experimental data. This method provides point estimates as well as joint probability regions. The validity of this method was approved for the statistically justified and best estimation of the rate parameters in copolymerization systems. Statistical analysis indicated that, although copolymer composition is well described by the terminal unit model (TUM), the rate data are not. Like many other systems recently examined, the data were well represented by the implicit penultimate unit effect (IPUE) model of Fukuda and coworkers. It was found that the coupled rate parameter k̄p/k̄ italict0.5 is greater than the TUM predictions, whereas most of the previous systems studied have coupled rate parameters lower than those predicted by the TUM. An interactive computer simulator for parameter estimation was developed, which is run in two modes of estimation and prediction and is capable of receiving input data from both keyboard and databank. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1260–1272, 2004

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“…Since the order of magnitude of the termination rate parameter, $\bar k_t$ , is large, for the sake of clarity to show deviations, the computed values of this parameter are also shown in Figure 8 as $\log (\bar k_t )$ . It is clear that the termination rate parameter can be well represented by a simple weighted average of the homotermination rate constants:45 …”

Section: Resultsmentioning

confidence: 99%

A Two‐Step Interval and Modified Rosenbrock Method for Kinetic Parameter Estimation in Copolymerization Systems: A Robust and Reliable Approach

Habibi

Vasheghani‐Farahani

2004

Macro Theory & Simulations

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Summary: The kinetics of solution free radical copolymerization of isobutyl methacrylate (i‐BMA) and lauryl methacrylate (LMA) in benzene, initiated with 2,2‐azoisobutyronitrile (AIBN) were studied at different monomer feed compositions at low conversion levels. In order to avoid the complications of copolymerization kinetics, the pseudo‐kinetic rate constant method was applied in constant and variable volume polymerization systems. A two‐step procedure based on interval analysis and the modified Rosenbrock method was used to estimate the kinetic parameters of copolymerization. In the first step, initiation, coupled propagation‐termination and transfer rate parameters were determined from steady state kinetic equations using interval analysis. Since the objective function is non‐linear, non‐convex and has multiple local optima, a robust computational technique, based on the Interval Newton/Generalized Bisection (IN/GB) algorithm, was developed to solve this set of non‐linear algebraic equations. This method was used with mathematical and computational guarantees of certainty to find the global optimum. In the second step, the system of mole balance, population balance and moment equations, which are highly stiff ordinary differential equations, were discritized and solved by the modified Rosenbrock method. The results of the first computational step were inserted as an active or equality constraint in the second step to calculate the individual elementary rate parameters of the reaction. Statistical analysis indicated that the copolymer composition is well described by the terminal unit model (TUM), but the implicit penultimate unit effect (IPUE) model of Fukuda and coworkers is more suitable for describing the rate data. In contrast to most previously studied systems, it was found that propagation and coupled rate parameters are greater than those predicted by the TUM.Variation of number average molecular weight of the copolymer in polymerization system for various initial monomer feed compositions at different reaction times (solid lines are computed results).imageVariation of number average molecular weight of the copolymer in polymerization system for various initial monomer feed compositions at different reaction times (solid lines are computed results).

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Absolute propagation constants in vinyl polymerization

Cited by 10 publications

References 73 publications

Vulcanization of Butadiene Rubber by Means of Cyclic Disulfides. 2. A 2D Solid State HRMAS NMR Study on Cross-Link Structures in BR Vulcanizates

Vulcanization of Butadiene Rubber by Means of Cyclic Disulfides. 2. A 2D Solid State HRMAS NMR Study on Cross-Link Structures in BR Vulcanizates

Reactivation of precore mutant hepatitis B virus in chemotherapy-treated patients

A Two‐Step Interval and Modified Rosenbrock Method for Kinetic Parameter Estimation in Copolymerization Systems: A Robust and Reliable Approach

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