Ab initio study of poly(vinyl chloride) propagation kinetics: head-to-head versus head-to-tail additions.
The relative importance of head-to-head versus head-to-tail additions during the free-radical polymerization of vinyl chloride is determined by ab initio methods for different chain lengths of the polymer. First, a level of theory study is performed to determine cost-effective methods for the ab initio description of the propagation kinetics of vinyl chloride. The study includes the following DFT-based methods: B3LYP, B3PW91, BHandH, BHandHLYP, BLYP, BP86, MPW1K and MPW1PW91, in combination with double or triple zeta basis sets 6-31G(d) and 6-311G(d,p). Also, the more recently developed BMK and MPW1K functionals are included. The influence of diffuse functions is tested by comparison with the basis sets 6-31+G(d) and 6-311++G(3df,2p). The best-performing methods are B3LYP, B3PW91 and MPW1 K combined with the 6-31+G(d) basis set. The converged probability of head-to-head propagation (2 per 1000 monomer units) is put into relation with the experimental concentrations of defect structures. A comparison is made with the head-to-head (HH) content of fluorine-substituted polymers and poly(vinyl acetate). The ab initio calculations correctly predict the relative sequence of HH content among the various polymers.
Van Cauter
Karen
K
Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, 9000 Ghent, Belgium.
Van Speybroeck
Veronique
V
Waroquier
Michel
M