An investigation of hemibenzopinacolate radicals used in the synthesis of block-copolymers: ESR measurements and semiempirical calculations
| Autor: | L. Hajji, Ramiro Guerrero Santos, Jean‐Edouard Herz, Jean-Jacques André, Gérard Beinert, André Bieber |
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| Rok vydání: | 1995 |
| Předmět: |
Polymers and Plastics
Chemistry Organic Chemistry MNDO Charge density Condensed Matter Physics law.invention Inorganic Chemistry Nuclear magnetic resonance Polymerization law Materials Chemistry Physical chemistry Molecular orbital Electron paramagnetic resonance Ground state Spin (physics) Hyperfine structure |
| Zdroj: | Macromolecular Theory and Simulations. 4:1105-1126 |
| ISSN: | 1521-3919 1022-1344 |
| DOI: | 10.1002/mats.1995.040040607 |
| Popis: | Hemibenzopinacolate radicals may be incorporated in a polymer chain and the latter used as a macromolecular initiator. Kinetics of polymerization are strongly dependent on the substitution of the pinacolate. A large family of substituted (CH 3 ) 3 SiOC(C 6 H 5 ) 2 radicals has been synthesized and studied by electron spin resonance (ESR) and semiempirical molecular orbital calculations. ESR spectra are well resolved and, except for one derivative, allow an unambiguous determination of the hyperfine coupling splitting (HFS) constants. The ground state properties have been calculated within different approximations, namely MNDO, AM1 and PM3 for the geometry optimization and INDO for spin density. Geometries obtained within AM1 and PM3 approximations are satisfactory. The HFS constants evaluated using McConnell type relations and spin densities are in a quite good agreement with the experimental ones. It turns out that the effect of substitution on kinetics of polymerization cannot be attributed to any drastic change in the charge distribution. |
| Databáze: | OpenAIRE |
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