The Behaviors Investigation Of Free Radical Polymerization With Ionic Liquids As Solvent

Ionic liquids(ILs)as a green solvent has unique properties such as non-toxicity,non-volatility,thermal stability,recyclability and so on.And ILs has a good compatibility with many inorganic compounds,organic compounds and polymers,so it can be used as solvent to replace organic solvent not only applied in electrochemical synthesis,chemical synthesis and separation,and organic synthesis,also in the free radical polymerization.In addition,a significant enhancement of polymerization rate and molecular weight that is often observed in the free radical polymerization with ionic liquids as solvent compared with the traditional organic solvents.The interesting phenomenon has attracted the attention of many scholars at home and abroad,but so far it has not been clarified the reason and mechanism for a significant molecular weight and rate enhancement that is observed when polymerization is conducted in ionic liquids.In view of the many advantages of ionic liquids and their potential applications in the field of polymer synthesis,an in-depth study on the free radical polymerization behaviors in ionic liquids is warranted to conduct to clarify the underlying cause and mechanism of the molecular weight and rate enhancing effect.The free radical polymerization of methyl methacrylate(MMA)with ionic liquids as solvent as the research object,was investigated the effect of polymerization temperature,ionic liquid concentration,the types of anion and cation of ionic liquid on the polymerization behaviors and molecular weight of product compared with that of in bulk and toluene,clarified the reason for ionic liquid leading to the enhancement of rate and molecular weight.In this paper,the improved compatibility experiment and the simulation of diffusion chain termination experiment are used to verify the proposed ideas.On this basis,a mechananism illumination was put forward.The conclusions are as follows:(1)Ionic liquids can indeed improve the polymerization rate and the molecular weight of polymer product Poly(methyl methacrylate)PMMA compared with the free radical polymerization of MMA with toluene as solvent,and the molecular weight of the product synthesized in ionic liquids is two times higher than that of in toluene.(2)The polymerization behaviors of MMA in ionic liquids are similar to that of bulk polymerization of MMA,and both of them show a remarkable auto-acceleration characteristic.An earier auto-acceleration effect is observed in the free radical polymerization in ionic liquids than that of in bulk polymerization.The higher the ionic liquid concentration is,the earlier the auto-acceleration effect appears.(3)A significant enhancement of polymerization rate in the free radical polymerization with ionic liquids as solvent results from auto-acceleration effect in free radical polymerization conducted in ionic liquids,and auto-acceleration effect leads to increasing the molecular weight of the polymerization product.(4)The reason for an earlier auto-acceleration effect appearing in the reaction with ionic liquids as solvent and a significant enhancement of rate and molecular weight can be attributed to the decrease of the solubility of products in reaction system caused by the addition of ionic liquids.