Structure of Monodisperse and Bimodal Brushes
Structure of Monodisperse and Bimodal Brushes
复制标题
单分散和双峰刷的结构
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
A. A. V. Well
中科院分区：
文献类型：
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作者：
E. Currie;M. Wagemaker;M. Stuart;A. A. V. Well
用中子反射率研究了由聚环氧乙烷（PEO）组成的单分散和双峰电刷在空气/水界面上的结构，并将结果与Scheutjens-Fleer自一致场晶格模型预测的结构进行了比较。在低接枝密度和中等接枝密度下，单分散PEO电刷的单体密度分布呈块状，并有一个扩展的尾部区域，其中密度平滑地衰减到零。然而，在高接枝密度下，正如解析自洽场模型所预测的那样，剖面主要是抛物线形的。实验测量的分布与Scheutjens-Fleer模型预测的分布在数量上是一致的。研究了不同接枝密度下双峰刷的三种链长比和混合比。结果表明，在一定的接枝密度下，双峰刷的长链比单分散刷的长链更长。这种额外的拉伸随着小块长度的增加或小块的比例的增加而增加。在双峰刷的情况下，Scheutjens-Fleer和测量密度剖面之间的一致性也很好。
The structure of monodisperse and bimodal brushes consisting of poly(ethylene oxide) (PEO) at the air/water interface is investigated with neutron reflectivity, and the results are compared with the structure predicted by the Scheutjens-Fleer self-consistent-field lattice model. The monomer density profile of a monodisperse PEO brush at low and intermediate grafting densities is block-like with an extended tail region in which the density smoothly decays to zero. At high grafting densities, however, the profile is predominantly parabolic, as predicted by analytical self-consistent-field models. Quantitative agreement is found between the experimentally measured profiles and those predicted by the Scheutjens-Fleer model. Bimodal brushes are investigated for three chain length ratios and mixing ratios at various grafting densities. It is concluded that at a given grafting density, the long chains are more extended in bimodal brushes than in monodisperse brushes at the same grafting density. This additional stretching increases with increasing length of the smaller block or increasing fraction of smaller blocks. The agreement between the Scheutjens-Fleer and measured density profiles is also good in the case of bimodal brushes.