| Synthesis of hydroxy-terminated polydimethylsiloxane with continuous technique is an advanced process in the world. Its feature is that the ring-opening polymerization of cyclosiloxane catalyzed by base and hydrolysis by water take place simultantaneously.Water in the basic catalyzed polymerization of cyclosiloxane can be coordinated with the reaction active center to terminate the reaction, so the research of ring-opening polymerizaion of cyclosiloxane has been performed mainly in the absence of water, and that in the presence of water is almostly not done. In this paper, the polymerization kinetics, reaction mechanism, viscosity, molecular weight and MWD of the ring-opening polymerization of cyclosiloxane in the presence of water will be investigated expermentally and analyzed mechanistically in detail.The thesis includes the following aspects:Based on the calibration curve established, the conversion data of reaction mixtures were determined by Gel Permeation Chromatography (GPC) method. The kinetics of polymerization was researched, and the following results were obtained: temperature, catalyst concentration, water concentration have evidently influence on the reaction rate, ultimate conversion of polymerization and ultimate molecular weight of polymer. The reaction rate and the catalyst concentration are in one-order relation in certain range of catalyst concentration.The reaction mechanism of the ring-opening polymerization of cyclosiloxane in the presence of water was proposed. And the polymerization kinetic model was obtained based on mechanism analysis. The kinetic model was successfully applied to quantitatively calculate the variation of active center concentration with time, and three periods including sluggish period, increasing period and declining period, were observed. The complex formed from polysiloxane and water was verified by infrared spectroscopy (IR), and the amounts of active centres decrease with increase of conversion, were measured with gas/mass chromatography (GC/MS).It indicates that the concentration of active centers decreases with the temperature and the water concentration increasing, and the concentration of active centers increases with thecatalyst concentration increasing.Based on the mechanistic research of the ring-opening polymerization of cyclosiloxane in the presence of water described above, the concentration medol of hydroxy-terminated was obtained. Using this concentration model of hydroxy terminated, the molecular weight model of the ring-opening polymerization of cyclosiloxane in the presence of water was established:It is discovered that the model curve is in agreement with the experimental data, it also verifies the validity of the mechanism of polymerization. The formula of the chain transfer constant k3, k3 = 1.94 x1015e-115831/RT, was obtained too. And the concentrations of catalyst and water did not influence on the value of k3. The relationships between conversion rate and the rate of hydroxy terminated created were carefully studied at various reaction conditions too.The equation of molecular weight distribution of the ring-opening polymerization of cyclosiioxane in the presence of water was derived. It is discovered that it is a typical Flory distribution, and the theoretical distribution curves are coincident with experimental data. And it is affirmed that the influence of polymerization conditions on the molecular weight distribution are not remarkable.The mathematical model of viscosity - molecular weight - conversion (vmc model) has been established: logF = X% (-8.08log Mw + 47.5). And it is discovered that the model curve highly accords with the experimental data. So the engineering design can been directed according to the vmc model. Based on the research, it outcomes that viscosity of reaction mixture monotonously increases together with conversion, it can be turned into reality that the ring-opening polymerization of cyclosiioxane in the presence of water is performed by continuous process. It is found that the influe...
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