含咪唑离子盐的环辛烯在离子液体中开环易位聚合微观研究

KINETICS OF RING-OPENING METATHESIS POLYMERIZATION OF CYCLOOCTENE DERIVATIVE IN IONIC LIQUID

用核磁共振方法研究了带电荷的环辛烯单体在离子液体和CDCl3中开环易位聚合反应的微观特征，根据单体在化学位移δ=5．66～5．58处双键氢积分峰面积的减少和聚合物主链上不饱和双键氢移至高场δ=5．38～5．39处峰面积积分的增加来表征聚合反应的情况．检测和记录了单体在有离子液体参与的条件下均相聚合反应和在CDCl3中的异相聚合反应过程，根据在不同反应体系中Grubbs第二代崔化剂中与Ru相连的苯亚甲基上氢在核磁图谱上δ=19．2处的峰型变化，探讨在两种介质中的不同聚合行为．研究表明，该单体在离子液体介质中的均相聚合有可控聚合的微观特点，并通过ln[M]0/[M]与反应时间的关系曲线，证实了反应的活性特征．

Ring-opening metathesis polymerization （ROMP） is a widespread tool to synthesize well-defined and highly funetionalized polymers. Recently, the ROMP of 5-substituted eyelooctene with the pendant of imidazolium salt catalyzed by Grubbs second generation catalyst [ RuCl2 （ PCy3 ） （SIMes） （CHPh） ] in CH2 Cl2 and ionic liquid was reported. The polymerization, which was carried out in CH2Cl2, afforded much higher number average molecular weights （Mn） and a much broader molecular weight distribution （PDI） than those expected for a living polymerization. These results imply that, with funetionalized eyelooetene monomer propagation is significantly faster than initiation resulting in a poor initiation efficiency. Additionally, the broadening PDI of polymers may be due to its propensity to perform intramoleeular backbiting reactions. This is a general phenomenon in ROMP initiated with [ RuCl2 （ PCy3 ） （SIMes） （CHPh） ] in conventional organic solvents. However, the polymerization, which was carried out in ionic liquid, afforded improved control over the molecular weight and polydispersity of the resultant product （PDI 〈 1.4） .This polymerization showed many of the characteristics of a living system which prompted us to look more closely at the kinetics of this particular system. The first investigation for kinetics of the initiation and propagation of ring-opening metathesis polymerization of 3-methyl- 1- [ （5-eyelooetenyl） oxyearbonylmethylene ] -imidazol- 1-ium tetrafluoroborate catalyzed by [ RuCl2 （ PCy3 ） （SIMes） （CHPh）] in ionic liquid and CDCl3 was carried out by I H-NMR spectroscopy measurement. The decrease in the monomer concentration over time was tracked by the monitoring of the decrease in the resonance of the alkenes protons on the eyelooetenes ring which appeared at 3 = 5.5 - 5.7 relative to an internal standard of CDCl3 . These proton signals shifted upfield to approximately 3 = 5.38- 5.39 as the undertaking of reaction, this indicated that the polymerization had occurred, and the monomer had turned to be polymer. The polymerization performances were much different in CDCl3 and ionic liquid.lH-NMR studies have revealed that the initiating earbene,which shows a signal for the alkylidine proton at 3 = 19.2 in CDCl3 , is converted into the propagating carbine with a remarkable peak change from broad to sharp over time. The multiplicity and broadening of the resonances are consistent with a multiplicity of overlapping environments associated with irregular living chain terminal. The polymerization was also monitored by ^1 H-NMR in ionic liquid, within the limits of NMR sensitivity, signals attributed to the propagating carbine （δ= 19.2） maintained a relatively same intensity throughout the polymerization which meant a constant concentration for the living propagating chain. The plot of In [ M ] 0/[ M ] versus reaction time was found to be linear in ionic liquid, and the results demonstrated the absence of chain termination on the timeseale of the polymerization and showed the polymerization was conducted with living characteristics. The reaction kinetic equation for the polymerization process in ionic liquid was also determined. The exact nature of the propagating species in ROMP is unknown, but we assume that the living characterization ＂is ascribed to the relatively slow propagation of monomer because of the interaction between the charge of monomer and medium of ionic liquid.