INVESTIGATION OF POLYIMIDE FORMATION FROM THE COMPLEXES OF THE DIESTER OF BENZOPHENONETETRACARBOXYLIC ACID WITH DIAMINES .7. ROLE OF THE O-CARBOXYLIC GROUP OF ACID DIESTER IN THE FORMATION AND IMIDIZATION OF H-COMPLEXES

The kinetics of thermal imidization of various H-complexes of semieste rs of bis(o-phthalic) acids with diamines was studied. The activation energy of the imidization was shown to increase with increasing pK(a) value of the diamine and E(a) value of the dianhydride and with decrea sing nucleophilicity of the alcohol used for the synthesis of H-comple xes. The experimental kinetic data and the results of quantum chemical calculations of the heats of formation of the initial H-complexes and transition states made it possible to propose a mechanism for the imi dization reaction. This mechanism takes into account the catalytic eff ect of the carboxylic group of the semiester in the o-position with re spect to the ester group.