Radeva Tsetska, Kamburova Kamelia
Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.
J Colloid Interface Sci. 2007 Apr 15;308(2):309-17. doi: 10.1016/j.jcis.2007.01.028. Epub 2007 Jan 19.
The buildup of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on beta-FeOOH colloidal particles was investigated by means of electro-optics and electrophoresis. The films were built at different (acidic) pH in the absence of salt. We found that the thickness of the film grows linearly when the fully charged PLL (at pH 5.5) is combined with almost fully charged PGA (at pH 6.5), with a thickness of about 2 nm per single layer. When the fully charged PLL is combined with weakly charged PGA (at pH 4.5), the film thickness increases exponentially with the number of deposited layers. The thickness of the exponentially growing film increases to 300 nm after deposition of 16 layers. The exponential film growth is attributed to the ability of the PLL to diffuse "in" and "out" of the film bulk at each deposition step. The variation in the electrical polarizability of the film-coated particles was also monitored as a function of the number of adsorbed layers. The result reveals that the PLL chains, which can diffuse into the film bulk, have no measurable contribution to the electro-optical effect of the films terminated with PLL. It is only due to the polarization of counterions of the PLL adsorbed on the film surface.
通过电光和电泳手段研究了聚（L-谷氨酸）（PGA）和聚（L-赖氨酸）（PLL）多层膜在β-FeOOH胶体颗粒上的堆积情况。这些膜是在无盐条件下于不同（酸性）pH值下构建的。我们发现，当完全带电的PLL（在pH 5.5时）与几乎完全带电的PGA（在pH 6.5时）结合时，膜的厚度呈线性增长，每层厚度约为2 nm。当完全带电的PLL与弱带电的PGA（在pH 4.5时）结合时，膜厚度随沉积层数呈指数增加。在沉积16层后，指数增长的膜厚度增加到300 nm。指数膜生长归因于PLL在每个沉积步骤中能够在膜体中“扩散进”和“扩散出”。还监测了膜包覆颗粒的电极化率随吸附层数的变化。结果表明，能够扩散到膜体中的PLL链对以PLL终止的膜的电光效应没有可测量的贡献。这仅仅是由于吸附在膜表面的PLL反离子的极化。
