A Study on the Radical Polymerization of Vinyl Monomers by Unrestricted Frontier Molecular Orbital Method -Propagation Reaction-

Abstract

In order to explain theoretically the easiness of the polymerization of vinyl monomer, the perturbation energies, ΔE, of the reaction of CH₃CH-R with CH₂=CH-R were calculated by the unrestricted MO method. First, the geometries of the monomers and the radicals were obtained by ab initio unrestricted Hartree-Fock MO method. Then the parameters of MO (eigenvalus, net charges and 'coefficients) were calculated.
Δ was calculated by the unrestricted frontier MO method, according to the following ea uation,
ψ_α and ψ_β indicate the occupied frontier α-MO and the vacant frontier β-MO. R_r8, ε and 4Δ were estimated to be 2.3 Å, 2.3 and -3.9 eV, respectively. The calculated Δ Were coordinated with the activation energies, Ep_??_, of the radical propagation reaction in literature, and a straight line was obtained, as shown in Fig.4 (in Text). Accordingly, the relationship between Ep_??_ and Δ was established as the following equation, Ep_??_ =c-γΔE