Pseudokinetics for the copolymerization of butadiene and styrene produced using n-butyl lithium and N,N,N′,N′-tetramethylethylenediamine, considering different reactivities of the structural units

The anionic solution copolymerization of butadiene and styrene prepared by anionic living polymerization using an initiator composed of n-butyl lithium, and N,N,N′,N′-tetramethylethylenediamine as active center modifier was modeled as a tetrapolymerization. The kinetic model proposed considering that the reactivity of the active sites is different because of varying configurations cis, trans, vinyl, and styryl. From the reaction scheme expressions to rate of monomers consumption, microstructure and dyad formation were obtained. With the first-order Markov model, the expressions for the fraction of active sites and dyad distribution as a function of the conditional probabilities were obtained. Therefore, the model proposed is different to kinetic models previously reported, because it allows obtaining the parameters kinetic in order to know the distribution of the isomeric species presents in the copolymerization of butadiene and styrene, and the intrinsic reactivity of configurational active sites. The rate constants were determined by fitting to the conversion and dyad experimental data using the nonlinear least square method. The experimental data reported in the literature, monomer conversion and microstructure, in addition to dyad sequence distribution were correctly predicted.