Buron C C, Filiâtre C, Membrey F, Perrot H, Foissy A
LCMI, Université de Franche-Comté, 16 route de Gray, 25030 Besancon cedex, France.
J Colloid Interface Sci. 2006 Apr 15;296(2):409-18. doi: 10.1016/j.jcis.2005.09.034. Epub 2005 Nov 15.
This work aimed to the determination of weight uptakes and charge balance in the course of successive deposition of polyelectrolytes, using the so-called self-assembled multilayer technique. Polyelectrolytes were the quaternized polydimethylaminoethyl methacrylate chloride, (MADQUAT) and poly(acrylic acid) (PAA). Experiments were made at pH 5.5 in NaCl solutions between 10(-3) and 10(-1) M. Deposits (5 bilayers) on a gold substrate were monitored using a quartz crystal microbalance (QCM) and optical fixed-angle reflectometry. Analysis of data lead to the determination of the sensitivity factor of the reflectometric output. QCM allowed the direct measurement of weight uptakes in 10(-3) and 10(-2) M solutions, while the viscoelastic properties of the film did not look appropriate for the measurement in 10(-1) M solutions. The layer-by-layer uptakes and charge balances in 10(-3) and 10(-2) M solutions revealed a large contribution of the counterions in the neutralization of the electrical charge in the film, more so for the highly charged MADQUAT polymer. The difference between two successive polymer charge densities increased significantly with the layer number and the electrolyte concentration. The increase of NaCl concentration induced an increase of MADQUAT but reversely a decrease of PAA deposits. The results were consistent with the determining influence of the salt in polyelectrolyte adsorption, both with regards to the concentration and the type of ions that has been well demonstrated in the literature. This work also draws attention to the role of small ions in the structural and application properties of self-assembled multilayer films.
本研究旨在利用所谓的自组装多层技术，测定聚电解质连续沉积过程中的重量吸收和电荷平衡。聚电解质为季铵化聚甲基丙烯酸二甲氨基乙酯氯化物（MADQUAT）和聚丙烯酸（PAA）。实验在pH 5.5的NaCl溶液中进行，浓度范围为10⁻³至10⁻¹M。使用石英晶体微天平（QCM）和光学固定角反射仪监测金基底上的沉积物（5个双层）。数据分析得出反射测量输出的灵敏度因子。QCM可直接测量10⁻³和10⁻²M溶液中的重量吸收，而薄膜的粘弹性性质似乎不适合在10⁻¹M溶液中进行测量。10⁻³和10⁻²M溶液中的逐层吸收和电荷平衡表明，抗衡离子在中和薄膜中的电荷方面起了很大作用，对于高电荷的MADQUAT聚合物更是如此。两个连续聚合物电荷密度之间的差异随层数和电解质浓度显著增加。NaCl浓度的增加导致MADQUAT沉积增加，但PAA沉积反而减少。结果与盐在聚电解质吸附中的决定性影响一致，这在文献中关于离子浓度和类型方面已得到充分证明。这项工作还提请人们注意小离子在自组装多层膜的结构和应用性质中的作用。
