Kinetic study of the Knoevenagel condensation applied to the synthesis of poly[bicarbazolylene-alt-phenylenebis(cyanovinylene)]s

The Knoevenagel condensation has been applied to the synthesis of [bicarbaz olylene-altphenylenebis(cyanovinylene)l copolymers and their model compound s. The kinetic study at 65 degreesC showed a very complex reaction: the app arent order was found to change with the modification of experimental condi tions. In methanol the reaction rate is governed by the dissociation step o f the active methylene compound (step 1 of the reaction mechanism). In T:KF /MeOH mixtures, the rate-determining step is a result of the relative rate ratio step 1/step 2. The influence of several dipolar interactions between the active methylene compounds, the aldehyde monomers, and the solvents use d is discussed along with the effects of the polarity and the concentration of comonomers on reaction rates. More importantly, the possibility to cont rol precisely the reaction rate via the appropriate choice of the dielectri c constant of the initial medium is emphasized. Finally, the observed resul ts obtained have been transposed to the synthesis of wholly THF-soluble con jugated copolymers, which can reach molecular weight equal to 25 000, in po lystyrene equivalent.