Interdiffusion in Polyelectrolyte Multi layers
Interdiffusion in Polyelectrolyte Multi layers
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DOI：
10.1021/ma101279q
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发表时间：
2010-09-14
期刊：
影响因子：
5.5
通讯作者：
Helm, Christiane A.
中科院分区：
文献类型：
--
作者：
Soltwedel, Olaf;Ivanova, Oxana;Helm, Christiane A.
利用中子反射率，在纳米尺度上描述了聚电解质多层膜的内部结构。每层膜分别由x质子化聚阳离子/多阴离子双层膜和y氢化聚阴离子/阳离子双层膜组成。双层膜的数目N=x+y保持不变；块之间的界面位置是系统变化的。聚阴离子为聚苯乙烯磺酸盐(PSS)，聚阳离子为聚烯丙基胺盐酸盐(PAH)或聚二烯丙基二甲基氯化铵(PDADMAC)。通常，前四到五个双分子层比平均双分子层厚度薄，但终止的三个双分子层有时会更厚。在核心区，双层厚度是恒定的。薄膜/空气界面附近的内部粗糙度最小，并且随着远离薄膜/空气界面的双层数的增加而增加。这表明每个沉积步骤都促进了支撑层的相互扩散。在所选择的制备条件下，PDADMAC/PSS比PAH/PSS的内部粗糙度增加更多，扩散常数相差2个数量级。
Using neutron reflectivity, the internal structure of polyelectrolyte multilayers is described on the nanoscale. Each film consists of a protonated and a deuterated block, built from x protonated and y deuterated polycation/polyanion bilayers, respectively. The number of bilayers N = x + y is kept constant; the position of the interface between the blocks is varied systematically. The polyanion is poly(styrenesulfonate) (PSS), and the polycation is poly(allylamine hydrochloride) (PAH) or poly(diallyldimethylammonium chloride) (PDADMAC). Always, the first four to five bilayers are thinner than the average bilayer thickness, but the three terminating bilayers are sometimes thicker. In the core zone, the bilayer thickness is constant. The internal roughness is smallest next to the film/air interface and increases with the number of bilayers away from the film/air interface. This suggests that each deposition step promotes the interdiffusion of the supporting layers. At the selected preparation conditions, the internal roughness increases more for PDADMAC/PSS than for PAH/PSS; the diffusion constants differ by 2 orders of magnitude.