Research Of4-Dimethylamino Pyridine/Dimethyl Sulfoxide System Catalyzed Polymerization Of Acrylonitrile

Polyacrylonitrile (PAN) is a kind of polymer material that widely appliedin plastic, fiber and elastomer areas; meanwhile, it is an important precursor ofcarbon fiber. PAN can be prepared through several mechanisms, includingradical, anionic, coordinative polymerization and controlled radicalpolymerization as atom transfer radical polymerization (ATRP) and grouptransfer polymerization (GTP). Up to now the commercial available PAN isprimarily prepared via radical polymerization. The processes include emulsion,solution, suspension polymerization and aqueoussuspention polymerization.However, in these methods a lot of problems exist, such as too many sidereactions, difficult in controlling polymerization speed, microstructure ofpolymer, molecular weight and molecular weight distribution.In this thesis, we used DMAP/DMSO system to catalyze thepolymerization of acrylonitrile (AN) and succeeded in preparing PAN withlinear structure. The reaction processed in0~60℃showed somecharacteristics of living polymerization. The conversion rate was10%~90%.Molecular weight was5×103~5×104with distribution of1.48~2.94. Thecomponent of reaction system is not complex. The condition was temperatewith proper polymerization rate. The conversion rate was relatively high andthe product was pure with high molecular weight. The controlling ofmolecular weight could be achieved at some level.The polymerization reaction showed an interesting phenomenon that themolecular weight of polymer would increase while the content of DMAP inthe system increased. We believe that the reacting mechanism of this reactionis different with radical polymerization and traditional anionic polymerization.The products were characterized via nuclear magnetic resonance (NMR), gelpermeation chromatography (GPC), time of fly mass spectrum and elemental analysis. The reaction mechanism was discussed with the result of series ofexperiments. We believe that DMAP and DMSO formed a coordination andcatalyzed AN to form tetramer. The tetramer continue polymerizing andfinally turn into PAN.