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The effect of molecular architecture of polymeric dispersants on the stabilization and rheology of dispersions.

机译：聚合物分散剂的分子结构对分散体稳定性和流变性的影响。

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摘要

In this work, we have investigated the effect of polymer molecular architecture on the stabilization and rheology of dispersions. Well-defined model systems of functionalized polystyrene chains with narrow molecular weight distributions and monodisperse silica particles have been used.;Different sizes of monodisperse silica particles were prepared by the hydrolysis of tetraethylorthosilicate. Different molecular weight linear and bilinear alkoxysilane functionalized-polystyrenes were synthesized by anionic polymerization techniques. Bilinear alkoxysilane-polystyrenes were defined as polystyrenes with alkoxysilane functional groups located exactly in the middle of the chains. The alkoxysilane functionality allowed reaction with surface silanol groups to chemically graft the polystyrene onto silica surfaces.;The effect of molecular weight on dispersion stability, as monitored by the dispersion turbidity as a function of time, showed that the dispersion stability increased with increasing molecular weight up to molecular weights of 10,000 to 30,000, after which little additional effect was found. These critical molecular weights were found to be dependent on particle size and molecular architecture. Bilinear polystyrenes showed better dispersion efficiency than did linear polystyrenes having similar arm molecular weights. The effect of molecular architecture on stabilization diminished as the dispersed medium approached theta conditions for polystyrene.;In dilute suspensions, the deviation of the measured relative viscosity from the value calculated from the Einstein equation could be correlated with the stabilization efficiency of the polymer. The results found for the rheological properties were consistent with results obtained from the stabilization studies. The unstabilized particles exhibited wall-slip and critical shear thinning phenomena, while the rheological properties of stabilized silica suspension showed both shear thinning and shear thickening behavior. The thickness of the polymer surface layer, as calculated from the high shear viscosity of concentrated suspensions, increased with increasing polymer concentration on the silica surface. At high stabilizer surface coverage, the calculated polymer layer thickness indicated that the polymer chains were in a partially extended conformation. At low stabilizer surface coverage, the apparent decrease in stabilizer thickness suggested that inter-mixing of grafted polymer chains between neighboring particles occurred.
机译：在这项工作中，我们研究了聚合物分子结构对分散体稳定性和流变性的影响。使用了分子量分布窄，官能化的聚苯乙烯链和单分散二氧化硅颗粒的定义明确的模型系统。通过原硅酸四乙酯的水解制备了不同尺寸的单分散二氧化硅颗粒。通过阴离子聚合技术合成了不同分子量的线性和双线性烷氧基硅烷官能化聚苯乙烯。双线性烷氧基硅烷-聚苯乙烯定义为具有恰好位于链中间的烷氧基硅烷官能团的聚苯乙烯。烷氧基硅烷官能团允许与表面硅烷醇基反应将聚苯乙烯化学接枝到二氧化硅表面上；分子量对分散体稳定性的影响（通过分散体浊度随时间的变化监测）表明，分散体稳定性随分子量的增加而增加分子量高达10,000至30,000，此后几乎没有发现其他作用。发现这些临界分子量取决于粒度和分子结构。双线性聚苯乙烯比具有相似臂分子量的线性聚苯乙烯表现出更好的分散效率。当分散介质接近聚苯乙烯的theta条件时，分子结构对稳定性的影响减弱。在稀悬浮液中，测得的相对粘度与爱因斯坦方程计算值的偏差可能与聚合物的稳定效率相关。流变性质的结果与稳定化研究的结果一致。未稳定化的颗粒表现出壁滑和临界剪切稀化现象，而稳定化的二氧化硅悬浮液的流变特性表现出剪切稀化和剪切增稠行为。由浓缩悬浮液的高剪切粘度计算出的聚合物表面层的厚度随二氧化硅表面上聚合物浓度的增加而增加。在高稳定剂表面覆盖率下，计算的聚合物层厚度表明聚合物链处于部分延伸的构型。在低稳定剂表面覆盖率的情况下，稳定剂厚度的明显降低表明在相邻颗粒之间发生了接枝聚合物链的相互混合。

著录项

  • 作者

    Yang, Zhiqi.;

  • 作者单位

    Michigan Technological University.;

  • 授予单位 Michigan Technological University.;
  • 学科 Chemistry Physical.;Chemistry Polymer.
  • 学位 Ph.D.
  • 年度 1995
  • 页码 141 p.
  • 总页数 141
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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