Accurate ab initio prediction of propagation rate coefficients in free-radical polymerization : Acrylonitrile and vinyl chloride

摘要: Abstract A systematic methodology for calculating accurate propagation rate coefficients in free-radical polymerization was designed and tested vinyl chloride acrylonitrile polymerization. For small to medium-sized polymer systems, theoretical reaction barriers are calculated using G3(MP2)-RAD. larger G3(MP2)-RAD can be approximated (to within 1 kJ mol −1 ) via an ONIOM-based approach which the core is studied at substituent effects modeled with ROMP2/6-311+G(3df,2p). DFT methods (including BLYP, B3LYP, MPWB195, BB1K MPWB1K) failed reproduce correct trends enthalpies molecular size, though KMLYP showed some promise as a low cost option very large systems. Reaction rates standard transition state theory conjunction one-dimensional hindered rotor model. The harmonic oscillator approximation shown introduce error of factor 2–3, would suitable “order-of-magnitude” estimates. study chain length indicated that had largely converged their long limit dimer radical stage, inclusion primary penultimate unit sufficient practical purposes. Solvent effects, COSMO model, were found relatively minor. overall reproduced available experimental data both these monomers 2.