1,3-戊二烯阳离子聚合引发反应的研究

INITIATION PROCESS FOR THE CATIONIC POLYMERIZATION OF 1,3 PENTADIENE

研究了以Ａｌ（ＯＴｆ）３引发的１，３－戊二烯（ＰＤ）在二氯甲烷中的阳离子聚合引发过程。该引发反应按引发剂中残余的质子给予体（Ｈ２Ｏ和ＨＯＴｆ）与引发剂形成的Ｈ２Ｏ／Ａｌ（ＯＴｆ）３和ＨＯＴｆ／Ａｌ（ＯＴｆ）３引发体系按共引发机理进行，聚合反应因此存在由两种引发体系产生的两种活性中心（１和２）。活性中心１的链增长速率较慢并生成较大分子量的聚合物，活性中心２反应速率较快但生成的聚合物具有较低的分子量。ＰＤ在非极性的正己烷中的聚合反应只存在活性中心１，表明聚合反应按残余水的共引发机理进行。

Polymerizations of 1,3 pentadiene(PD) initiated by Al(OTf) 3 were carried out in methylene chloride at 20 ℃. Investivations show that the polymerization is initiated by coinitiation of both H 2O/Al(OTf) 3 and HOTf/Al(OTf) 3 initiating systems where H 2O and HOTf are residual impurities contained in the initiator. H 2O/Al(OTf) 3 initiating system gives rise to active specie 1 which propagates relatively slowly and results in higher molecular weight polymers, and HOTf/Al(TOf)3 system generates specie 2 which give a faster polymerization but a polymer of lower molecular weight. The polymerization of PD induced by Al(OTf) 3 in n hexane seems to produce only specie 1, which indicates that this polymerization is initiated only by H 2O/Al(OTf) 3 initiating system.