APPLICATION OF AB-INITIO MO CALCULATIONS TO METHODS FOR PREDICTING REACTIVITY IN FREE-RADICAL COPOLYMERIZATION

Ab initio MO calculations have been performed utilizing several differ ent basis sets, viz. STO-3G, SV3-21G and TZV. The output from these ca lculations included the electronegativity of a set of vinyl monomers a nd their corresponding radicals formed by the addition of a hydrogen a tom or a methyl radical. These electronegativities were correlated wit h the Patterns of Reactivity alpha parameters and the Ito-Matsuda PI p arameters. The energy of formation (E(Y)) of a radical from the monome r was also calculated and correlated with the Patterns beta parameter and the Ito-Matsuda log k values. The polarity-electronegativity plots displayed a strong correlation. However, the correlation of E(Y) with beta was very poor and deteriorated with higher basis sets. We determ ined to improve matters by rescaling the Patterns scheme using styrene as the standard monomer. This attempt was unsuccessful as there were considerable problems with the Patterns scheme itself. They were attri buted to the kinetic database on which it is based, both reactivity ra tios and the Hammett sigma(p) parameters which are crucial to the succ essful application of the scheme. Correlations with the Ito-Matsuda pa rameters showed more promise but were limited by the amount of experim ental data available.