Development of Polycondensation via Chain Reaction

It is difficult to obtain molecular weight-controlled polymers with narrow molecular weight distribution in polycondensation, which proceeds in a step polymerization manner. If polycondensation proceeds in a chain-growth reaction manner from an initiator like the polymerization of vinyl monomers or cyclic monomers, polymers having a defined molecular weight and narrow molecular weight distribution would be produced though essentially stable propagating end groups. We study two types of polycondensations which proceed via chain polymerization (condensative cahin polymerization) on the basic strategy that the electrophilic site of monomers having necleophilic and electrophilic sites becomes more reactive after the nucleophilic site reacts with another monomer. The first type of polycondensation is fluoride ion-catalyzed polycondensation of 4-trimethylsiloxybenzoyl chloride derivatives. The model reaction showed the propagating acid chloride was more reactive than the acid chloride of monomer. In the polymerization, however, polymer was precipitated during reaction because of low solubility of polymer. Therefore the chain polymerization behavior was not evaluated. The second type of polycondensation is palladium-catalyzed CO insertion polycondensation of 4-bromophenol derivatives. The model reaction showed that the model of propagating end were more reactive than the model of monomer electrophilic site. However, ester exchange reaction occurred. The polymerization was carried out in the presence of bromobenzene with the electron-withdrawing group as a initiator to yield low-molecular weight polymer, the GPC curve of which showed that polymerization took place via chain polymerization manner from the initiator in the initial stage.