Conformational switching of modified guest chains in polymer brushes.
Conformational switching of modified guest chains in polymer brushes.
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DOI：
10.1063/1.4816125
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发表时间：
2013-07
期刊：
影响因子：
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通讯作者：
D. Romeis;J. Sommer
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文献类型：
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作者：
D. Romeis;J. Sommer
使用一个数值准离格自洽场方法，描述了异质链的球形单体，我们研究的情况下，一个密集的接枝聚合物刷的自由链端的一部分被取代的改性端基不同的大小和溶剂选择性。我们可以证实从分子动力学模拟的观察，即在改变溶剂条件时，发生比单体大的端基的位置从“暴露”于溶剂的状态（在刷的顶部）到“隐藏”状态（在刷的内部）的切换。我们的数值方法可以详细研究的开关效应作为相关参数的函数，如接枝密度，链长，端基的大小和它们的体积分数。我们发现，开关效应增强长链，低分数的改性链，和大的端基。我们考虑的情况下，更详细地使用测试链的方法修改链的低分数。在这里，我们探索的最佳接枝密度作为一个功能的大小的端基，开关是最敏感的。对于比单体大至少3-4倍的端基，这些值可以在实验范围内。端基可以通过将纳米颗粒附着到刷链的最后一个单体上来实现。
Using a numerical quasi off-lattice self-consistent field method which describes heterogeneous chains of spherical monomers we study the case of a densely grafted polymer brush with a fraction of free chain ends being replaced by a modified end-group differing in size and solvent selectivity. We can confirm the observation from molecular dynamics simulations that upon changing the solvent conditions, a switching in location of end-groups which are bigger than monomers from a state "exposed" to the solvent (on the top of the brush) to a "hidden" state (inside the brush) takes place. Our numerical method allows a detailed study of the switching effect as a function of the relevant parameters, such as grafting density, chain length, size of end-groups and their volume fraction. We find that the switching effect is enhanced for long chains, low fractions of modified chains, and big end-groups. We consider the case of low fraction of modified chains in more detail using a test chain method. Here, we explore the optimal grafting density as a function of the size of the end-groups, where the switching is most sensitive. These values can be in the experimental range for end-groups which are at least 3-4 times bigger than the monomers. The end-groups can be realized by attaching nano-particles to the last monomer of a brush-chain.