The Oxidative Polymerization Of 2,6-dimethylphenol With Potassium Ferricyanide In Water

The solution polymerization of 2,6-dimethyl phenol(DMP)is widely used in industrial production of poly(2,6-dimethyl-1,4-phenylene oxide)(PPO),an important engineering plastics,however,the heat and mass transfer is hindered at the later period because of the high viscosity of the reaction system.Furthermore,both a solvent recovery process and an explosion proof reactor are required.The use of water as the reaction medium is environmentally friendly and PPO can be separated from water easily due to its insolubility in water.Therefore,the oxidative polymerization of DMP to form PPO using water as the reaction medium would be of significance.The oxidative polymerization of DMP in water at the action of potassium ferricyanide was studied and PPO was synthesized.The influences of temperature,sodium hydroxide and SDS concentration on yields of PPO and the by-product,4-(3,5-dimethyl-4-oxo-2,5-cyclohexadientlidene)-2,6-dimethyl-2,5-cyclohexadienone(DPQ),were studied and the factors that affected the selectivity of oxidative polymerization were elucidated.It was found that both PPO and DPQ yield increased with potassium ferricyanide concentration.The alkaline concentration in water influenced the yield and the molecular weight of PPO. The oxidative polymerization of DMP can occur only under the alkaline solution. Both the yield and the molecular weight of PPO increased with sodium hydroxide concentration firstly and then decreased.PPO with the high molecular weight was obtained after the addition of SDS,while the molecular weight of PPO was low without SDS in water.The yield of DPQ was low and the molecular weight of PPO was high at the temperature of 50℃.The kinetics of oxidative polymerization of DMP at the action of potassium ferricyanide was studied by potentiometric measurements.It was found that the temperature,potassium ferricyanide and sodium hydroxide concentration influenced the reaction rate of DMP.The reaction rate of DMP increased with the sodium hydroxide concentration.The influence of sodium hydroxide concentration on the oxidative potential of DMP was studied by cyclic voltammertry.It was found that with the increase of sodium hydroxide concentration,the oxidative potential of DMP decreased,indicating that the increase of sodium hydroxide concentration was beneficial to the oxidative polymerization of DMP.The reaction rate of DMP increased with increasing potassium ferricyanide concentration,while the reaction rate of DMP decreased with increasing potassium ferrocyanide concentration,with The initial oxidative polymerization rate of DMP increased with the increase of temperature.According to the initial oxidative polymerization rate and initial concentrations of DMP and potassium ferricyanide,the initial reaction rate constant (k₀)was calculated.An apparent activation energy was calculated to be 40.7 kJ·mol^-1 according to Arrhenius equation.Potassium ferricyanide was only an oxidant and its concentration was high during the oxidative polymerization of DMP.In the presence of a copper-amine complex the oxidative polymerization of DMP was also studied.The Stability of the copper-amine complex was studied by UV-Vis,and the influence of sodium hydroxide concentration and amine ligands on the reaction rate of DMP was determined by the oxygen-uptake measurement.