四氟乙烯等的水相沉淀调聚反应的聚合度方程及其模拟

对于非衰减或弱衰减的＂理想链转移体系＂,考虑生成的聚合物对气相空间的压缩作用,导出了采用稀水溶液沉淀聚合工艺（俗称的分散聚合和悬浮聚合）制备低分子质量聚四氟乙烯等一类调聚反应中的瞬时和累积数（质）均聚合度随聚合转化率变化的方程,并进行了讨论和模拟。结果显示：在恒压聚合期,聚合度可以呈逐渐升高的趋势,但也可以维持恒定或逐渐降低,链转移剂浓度则呈与此相反的变化;阐明了此类反应的链转移剂或聚合压力的选择原则为：CS/M]g=Mr,M/ρp,一般CS〈〈1;降压聚合期间,因CS〈〈1,链转移剂相对含量大幅度提高,聚合度急剧下降。贯穿整个聚合周期生成的聚合物粒子呈一种内外分子质量有别的核壳结构。结果有望对此类低分子质量聚合物的合成起到一定的理论指导作用,但对强衰减链转移体系可能误差较大。

Equation and Simulation of Degree of the Dilute Aqueous Solution Precipitation Telomerization of Tetrafluoroethylene

For a hypothetical ＂ideal chain transfer system＂that have a non degenerative or lower degenerative chain transfer process,considering the compressing effect of the generated polymer to the gas phase space,a relationship of instantaneous and cumulate number and weight average degree of polymerization in the preparation of low molecular weight polytetrafluoroethylene etc by dilute aqueous solution precipitation telomerization process（ commonly known as the suspension polymerization and dispersion polymerization process） with the change of polymerization conversion was derived and a discussion and simulation was carried out. Results showed that the degree of polymerization had the trend to gradually rise,but as well as could maintain constant or had the trend to gradually reduce during the constant pressure period of the polymerization,at the same time,the concentration of chain transfer agent took on a contrary trend. The selection principle of chain transfer agent or polymerization pressure of this kind of reaction was expounded ： CS/M]g= Mr,M/ ρP,commonly CS〈〈1. During the pressure reducing period of the polymerization,since CS〈〈1,the relative content of chain transfer agent will be greatly improved,so the degree of polymerization decreased sharply. The polymer particle generated throughout the polymerization cycle had a core- shell structure that inner and outer molecular weight were discriminating. The results could play a certain theoretical guidance function for the synthesis of this kind of low molecular weight polymers,but the errors may be larger for the strong degenerative chain transfer system.