Reactivities in Free-radical Polymerization

Bamford, C. H.

doi:10.1016/b978-0-08-096701-1.00079-3

Cited by 4 publications

(2 citation statements)

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“…The lack of similarity between TS and products would indicate little resemblance between the two and any relationship between reaction enthalpies and reaction rate seems unlikely. The DFT calculated exothermicity of MMA (−12.6 kcal/mol) is reasonably close to experiment (−13.0 kcal/mol) and similar experimental exothermicities for the other methacrylates seems reasonable for such a homologous series of reactions. The calculated Δ H rxn for all methods have only a small range of values (Table ), further supporting a minor enthalpic effect on the reaction rate for these systems.…”

Section: Resultssupporting

confidence: 77%

“…Reaction rates can be affected by steric effects, charge transfer, resonance stabilization of the radical reactants or products, and enthalpic effects. The importance of each varies depending on the particular reaction species. ,,,− Of these effects, reaction enthalpy by nature is actually a function of the other three and may therefore be a combination of their collective influence …”

Section: Resultsmentioning

confidence: 99%

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A Quantum Mechanical Study of Methacrylate Free-Radical Polymerizations

Miller

Holder

2010

J. Phys. Chem. A

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Theoretical calculations at the semiempirical and ab initio levels of theory have been completed for a series of methacrylate compounds reported in the literature as measured by pulsed-laser initiated polymerization in conjunction with size-exclusion chromatography (PLP-SEC). Modeling includes calculation of the Gibb's free energies (ΔG(‡)) and activation energies (E(a)). These results were then compared to experimental results. Semiempirical ΔG(‡) using AM1-CI calculations successfully predicted relative activation energies (R(2) = 0.89). HF and DFT methods more accurately predicted absolute activation energies, but the relative values were less reliable. Accurate quantitative structure property relationship (QSAR) models for propagation rate coefficients, k(p), were developed using AM1-CI and DFT. The semiempirical model included two charge descriptors, partial negatively charged surface area (PNSA), and minimum net atomic charge for oxygen (R(2) = 0.959). The DFT information, which included two quantum chemical descriptors (1-electron reactivity index for carbon and point charge component of the molecular dipole) calculated from the ground state structure, had improved statistics (R(2) = 0.979). A second DFT model is reported for 10 hydrocarbon methacrylate structures based on the 1-electron reactivity index for carbon (R(2) = 0.979). Theoretical results were also analyzed to provide an explanation for the unexpectedly large experimental k(p) values observed in the case of larger methacrylate monomers.

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Section: Resultssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 99%

A Quantum Mechanical Study of Methacrylate Free-Radical Polymerizations

Miller

Holder

2010

J. Phys. Chem. A

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Reactivity Study of Elementary Steps in the Polymerization Mechanism of Acrylfuranic Compounds by Frontier Molecular Orbital Theory

Lange

Lozano

García‐Yoldi

2011

Macro Theory & Simulations

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A reactivity study of the most important elementary steps (propagation, intermolecular degradative transfer, and re‐initiation) in free‐radical polymerization of acrylfuranic systems, furfuryl acrylate (FA), and furfuryl methacrylate (FM), using the frontier molecular orbital theory is described. A qualitative explanation of reactivity trends of these steps for both systems is given based on absolute values of the SOMO/HOMO gap. The small difference between values of kp for FA and FM compared to that found for MA and MMA (${{k_{{\rm p}}^{{\rm (FA)}} } \mathord{\left/ {\vphantom {{k_{{\rm p}}^{{\rm (FA)}} } {k_{{\rm p}}^{{\rm (FM)}} }}} \right. \kern-\nulldelimiterspace} {k_{{\rm p}}^{{\rm (FM)}} }}< {{k_{{\rm p}}^{{\rm (MA)}} } \mathord{\left/ {\vphantom {{k_{{\rm p}}^{{\rm (MA)}} } {k_{{\rm p}}^{{\rm (MMA)}} }}} \right. \kern-\nulldelimiterspace} {k_{{\rm p}}^{{\rm (MMA)}} }}$) is justified semi‐quantitatively by applying a formulation for the change of energy in the transition state using second‐order perturbation theory.magnified image

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