Studies On The ATRP Reaction In Ionic Liquid-Based Microemulsions

Ionic liquids (ILs) are organic salts at room temperature or near room temperature which are entirely composed of the anion and cation. ILs are called"green solvent",because of their unique properties, such as low volatility (negligible vapor pressure) , excellent chemical stability , high thermal stability, recycling feature.Atom transfer radical polymerization( ATRP ) is an living/controlled radical polymerization method utilizing low state transition metal complexes as catalyst which can be used to synthesize narrow molecular distribution and polymer with specific terminal-function group. However, conventional aqueous microemulsion ATRP exists some problems: high concentration of transition-metal catalyst and surfactant are generally required, and it is hard to remove or re-use them.In this paper, ATRP reaction was conducted in the monomer/ionic liquid microemulsion ( ionic liquid as continuous ) system using the recyclable property of ionic liquid. After the polymerization was completed, the ionic liquid,surfactant and catalyst can be recycled. Microemulsion ATRP technology industrialization process is greatly promoted as the ionic liquid microemulsion system can be recycled and reused. The main work is as follows:1) Surfactant 1-dodecyl-3-methyl imidazoium bromide(a-Br) and ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate Bmim[BF4] were synthesized. And then the pseudo-ternary phase diagrams of ionic liquid/surfactant/monomer were determined by titration measurement, such as Bmim[BF4]/a-Br/St system, Bmim[BF4]/a-Br/MMA system at different temperatures2) Select a ratio in the phase diagram of Bmim[BF4]/a-Br/MMA system, and then prepare microemulsion. Conventional free radical polymerization was carried out in the microemulsion; the monomer and initiator were added in the ionic liquid mixture again after ionic liquid and surfactant was recycled. It is found that no significant change of molecular weight and particle size were observed.3) Reverse microemulsion ATRP reaction was carred out in the ionic liquid-based microemulsion: RATRP in the system met the Living / controlled polymerization characteristics by the research of polymerization kinetics. The polymer molecular weight, molecular weight distribution and particle size were all not significant changed compared to the first polymerization, after ionic liquid and catalyst were recycled repeatedly, indicating the recovered catalyst still has a very good activity. No residual surfactant and catalyst was in polymer nano-particles by NMR, XPS characterization. Residual copper content was between 49-85ppm by ICP, indicating that most of the catalyst had been effective separated and was re-recycled and reused.4) AGET ATRP reaction was preliminarily studied in this system. Ionic liquid-type ligands with the emulsification were firstly synthesized. Effects on the polymerization of the different hydrophilic ligands were studied: when conventional ligands such as bipy, PMDETA and BPMOA were used, the rules was similar to the reverse ATRP in the same system; when the new synthesized ionic liquid emulsifier-type ligands were used, the results were anti-conventional. Finally, ionic liquid and catalyst were recycled and reused, it was proved that catalyst still had good catalytic performance.