聚二甲基硅氧烷接枝二氧化硅球在聚二甲基硅氧烷熔体中的润湿性与流变行为的关联

Connecting the wetting and rheological behaviors of poly(dimethylsiloxane)-grafted silica spheres in poly(dimethylsiloxane) melts.

作者信息

Green David L, Mewis Jan

机构信息

Department of Chemical Engineering, University of Virginia, 102 Engineers Way, Charlottesville, Virginia 22904, USA.

出版信息

Langmuir. 2006 Nov 7;22(23):9546-53. doi: 10.1021/la061136z.

DOI:10.1021/la061136z

PMID:17073478

Abstract

Using dynamic light scattering, mechanical rheometry, and visual observation, the static wetting behavior of PDMS-grafted silica spheres (PDMS-g-silica) in PDMS melts is related to their rheology. A phase diagram is mapped out for a constant grafted chain length as a function of grafting density and free polymer chain length. The transition between stable and aggregated regions is determined optically and with dynamic light scattering. It is associated with a first-order wetting transition. In the stable region Newtonian behavior is observed for semidilute suspensions. The hydrodynamic brush thicknesses, deduced from viscosity measurements, correspond closely to values obtained from self-consistent field calculations for the various parameter values. At the transition, the brush collapses suddenly and shear-thinning and thixotropy appear. The rheology indicates a degree of aggregation that increases with increasing length of the free polymer, as suggested by the theory.

摘要

通过动态光散射、机械流变学和视觉观察，聚二甲基硅氧烷接枝二氧化硅球（PDMS-g-二氧化硅）在聚二甲基硅氧烷熔体中的静态润湿行为与其流变学相关。绘制了一个相图，该相图表示在接枝链长度恒定的情况下，接枝密度和自由聚合物链长度的函数关系。通过光学方法和动态光散射确定稳定区域和聚集区域之间的转变。它与一级润湿转变相关。在稳定区域，对于半稀悬浮液观察到牛顿行为。由粘度测量推导得到的流体动力学刷厚度与针对各种参数值通过自洽场计算获得的值密切对应。在转变点，刷突然塌陷，出现剪切变稀和触变性。流变学表明聚集程度随着自由聚合物长度的增加而增加，正如理论所暗示的那样。