Development of Polycondensation via Chain Reaction

在以分步聚合方式进行的缩聚中，难以获得具有窄分子量分布的分子量受控的聚合物。如果缩聚以链增长反应方式从引发剂进行，如乙烯基单体或环状单体的聚合，则将通过基本上稳定的增长端基产生具有限定分子量和窄分子量分布的聚合物。本文研究了两类通过链聚合（缩合链聚合）进行的缩聚反应：一类是氟离子催化的4-三甲氧基苯甲酰氯衍生物的缩聚反应。模型反应表明增长酰氯比单体酰氯反应活性高。然而，在聚合中，由于聚合物的低溶解度，聚合物在反应期间沉淀。第二类缩聚反应是4-溴苯酚衍生物的钯催化CO插入缩聚反应。模型反应表明增长端模型比单体亲电中心模型反应活性更高。然而，发生酯交换反应。以溴苯为引发剂，以吸电子基团为引发剂进行聚合，得到低分子量聚合物，GPC曲线表明聚合反应是以引发剂引发的链式聚合方式进行的。

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.