Kaewsaiha Ploysai, Matsumoto Kozo, Matsuoka Hideki
Department of Polymer Chemistry, Kyoto University, Kyoto 615-8510, Japan.
Langmuir. 2007 Jun 19;23(13):7065-71. doi: 10.1021/la063462k. Epub 2007 May 19.
The nanostructure of a spread monolayer of diblock copolymers of poly(hydrogenated isoprene) and poly(styrenesulfonate) at the air/water interface were studied by in situ X-ray reflectivity as a function of the brush density and salt concentration. When the monolayer was compressed beyond the "critical brush density", its nanostructure changed from a flat, adsorbed "carpet" layer to a "carpet + brush" structure. The critical brush density was found to be about 0.12 nm-2, independent the brush length and salt concentration under a low-salt condition. The brush formation behavior was considered to be controlled by an electrostatic interaction between polyelectrolyte chains rather than by a steric hindrance. This might be because the distance between the chains at the critical point is rather long and also because of the effect of the salt on the critical brush density. The critical brush density increased at higher added salt concentration beyond 1 M. As a result, we found a new structure transition behavior of the polymer brushes between carpet-only and carpet + brush structures, which was induced by salt addition. Finally, we succeeded in the controlled release of salt ions from the salted brush layer by changing the brush density by compression of the monolayer.
通过原位X射线反射率研究了聚（氢化异戊二烯）和聚（苯乙烯磺酸盐）的二嵌段共聚物在空气/水界面上扩展单分子层的纳米结构，该纳米结构是刷密度和盐浓度的函数。当单分子层被压缩超过“临界刷密度”时，其纳米结构从平坦的吸附“地毯”层变为“地毯+刷”结构。发现在低盐条件下，临界刷密度约为0.12 nm-2，与刷长度和盐浓度无关。刷的形成行为被认为是由聚电解质链之间的静电相互作用控制的，而不是由空间位阻控制的。这可能是因为临界点处链之间的距离相当长，也可能是因为盐对临界刷密度的影响。在添加盐浓度超过1 M时，临界刷密度增加。结果，我们发现了聚合物刷在仅地毯结构和地毯+刷结构之间的一种新的结构转变行为，这种行为是由添加盐引起的。最后，我们通过压缩单分子层改变刷密度，成功地实现了从加盐刷层中控制释放盐离子。
