羟基聚硅氧烷一步合成的速率研究

以四甲基氢氧化铵为催化剂，八甲基环四硅氧烷为单体，水为封端剂，一步合成羟基聚硅氧烷。采用凝胶渗透色谱(GPC)测定上述一步合成法的转化率，并建立转化率一时间关系曲线的模型函数(Bolzman函数),获得聚合过程中的重要特征参数：最大转化速率rm，极限转化率x(∞)等。研究表明．温度升高，rm加快，x(∞)降低；催化剂浓度增加，rm加快，x(∞)也增加，而转化速率与催化剂浓度在一定的范围内呈l级动力学关系；水浓度增加，rm降低，同时x(∞)也降低。

Study on the Rate for Preparing Hydroxy Terminated Polydimethylsiloxane in One-Step Process in the Presence of Water

Hydroxy terminated polydimethylsiloxane (PDMS) was directly synthesized from octamethylcyclotetrasiloxane (D_4) as monomer with tetramethyl ammonium hydroxide (TMAH) as catalysts under the conditions of high temperature, adding water and oxygen-off. It is named one-step process. The kinetics research has been performed by means of Gel Permeation Chromatography (GPC). Furthermore, Boltzman function as model function was built up, and was employed to fit the curves of cumulative conversion vs. reaction time. The parameters of polymerization were obtained too. On the basis of the conclusion described above, effects of reaction conditions on the kinetics of one-step process were investigated and the results were given as follows: the conversion rate increases and the ultimate conversion decreases with the temperature increasing; the conversion rate and the ultimate conversion increase with the catalyst concentration increasing; the conversion rate and the concentration of catalyst are one-order kinetics relationship in certain range;The conversion rate and the ultimate conversion decrease with the water concentration increasing.