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利用四苯基卟啉氯化铝(TPPAlCl)与双三苯基膦氯化铵(PPNCl)组成的二元催化剂催化二氧化碳与氧化环己烯共聚合,80℃下反应9 h,二氧化碳-氧化环己烯共聚物(PCHC)的收率为97.2%,分子量分布窄(Mw/Mn=1.12),但数均分子量仅为6.8×103.研究发现溶剂的浓度和极性变化对聚合过程中的链转移反应影响不大,而降低单体浓度,链转移反应明显减少,由此推断聚合过程中存在明显的向单体的链转移反应.进而采用基质辅助激光解析电离飞行时间质谱(MALDI-TOF/MS)对聚合物结构进行分析,提出了聚合反应过程中的链增长和链转移反应机理,即:在TPPAlCl/PPNCl二元催化剂催化二氧化碳与氧化环己烯共聚合反应中,除了引发剂引发单体聚合外,通过链转移又产生了其它新的活性中心,导致所生成的聚合物的数目远多于引发剂数目,而且络合铝离子在各聚合物链端的交换反应速率远大于链增长的速率,从而得到具有极窄分子量分布的聚碳酸酯.上述交换反应的可逆性是各分子链休止、增长交替进行的关键.
A binary catalyst consisting of tetraphenylporphyrin aluminum chloride (TPPAlCl) and bis (triphenylphosphine) ammonium chloride (PPNCl) was used to catalyze the copolymerization of carbon dioxide and cyclohexene oxide. After reaction at 80 ℃ for 9 h, The yield of hexene copolymer (PCHC) was 97.2% with a narrow molecular weight distribution (Mw / Mn = 1.12) but the number average molecular weight was only 6.8 × 103. It was found that the change of concentration and polarity of the solvent affected the polymerization of the chain The results showed that there was a significant monomer-to-monomer chain transfer reaction during the polymerization, and then MALDI-TOF / MALDI-TOF / MS), the mechanism of chain growth and chain transfer reaction in the polymerization reaction was proposed. In the copolymerization of carbon dioxide and cyclohexene oxide catalyzed by TPPAlCl / PPNCl binary catalyst, in addition to initiator initiation single In addition to the bulk polymerization, additional new centers of activity are created by chain transfer, resulting in much more polymers than the number of initiators, and the rate of exchange reaction of the complexed aluminum ions at each polymer chain end is much greater than that of chain growth rate, So as to obtain a very narrow molecular weight distribution of polycarbonate.The reversibility of the exchange reaction is the molecular chain of the rest, the key to the growth of alternating.