Horvath Andrew T, Horvath A Elisabet, Lindström Tom, Wågberg Lars
Royal Institute of Technology, Department of Fibre and Polymer Technology, SE-100 44 Stockholm, Sweden.
Langmuir. 2008 Jun 1;24(13):6585-94. doi: 10.1021/la800274w. Epub 2008 May 29.
The adsorption behavior of a low charge density cationic polyelectrolyte to cellulosic fibers has been studied. Cationic dextran served as a model polyelectrolyte, as it can be prepared over a range in molecular mass and charge density. The adsorption behavior of the cationic dextran was measured in electrolyte-free conditions using polyelectrolyte titration techniques. By fluorescent labeling the cationic dextran, the extent to which adsorption occurs inside the porous structure was further determined by fluorescent confocal laser scanning microscopy. Cationic dextran having a sufficiently low charge density adsorbed into the pores, although the extent the cationic dextran adsorbed was governed by the molecular mass. The adsorption behavior of the cationic dextran was also studied in various electrolyte concentrations. The adsorbed mass monotonically decreased with increasing electrolyte, as the electrostatic interaction with the substrate was more effectively screened. This behavior also suggests that the interactions between adsorbed polyelectrolyte chains, i.e. lateral correlation effects, are negligible for low charge density polyelectrolytes. Finally, the effect of having a preadsorbed layer of cationic dextran on the adsorption behavior was determined in electrolyte-free conditions using fluorescent double staining techniques. The preadsorbed cationic dextran had almost no effect on the adsorption of low molecular mass fractions. Low molecular mass fractions directly adsorbed into the pore structure, as opposed to adsorbing to a free surface and diffusing into the pores. It was also shown that cationic dextran can be selectively adsorbed to different locations, such that the surface of a porous substrate can be treated uniquely from the bulk.
研究了低电荷密度阳离子聚电解质对纤维素纤维的吸附行为。阳离子葡聚糖用作模型聚电解质，因为它可以在不同分子量和电荷密度范围内制备。使用聚电解质滴定技术在无电解质条件下测量阳离子葡聚糖的吸附行为。通过对阳离子葡聚糖进行荧光标记，利用荧光共聚焦激光扫描显微镜进一步确定了在多孔结构内部发生吸附的程度。电荷密度足够低的阳离子葡聚糖会吸附到孔中，尽管阳离子葡聚糖的吸附程度受分子量控制。还研究了阳离子葡聚糖在各种电解质浓度下的吸附行为。随着电解质浓度增加，吸附质量单调下降，因为与底物的静电相互作用被更有效地屏蔽。这种行为还表明，对于低电荷密度聚电解质，吸附的聚电解质链之间的相互作用，即横向相关效应可以忽略不计。最后，在无电解质条件下使用荧光双重染色技术确定了预先吸附的阳离子葡聚糖层对吸附行为的影响。预先吸附的阳离子葡聚糖对低分子量级分的吸附几乎没有影响。低分子量级分直接吸附到孔结构中，而不是吸附到自由表面并扩散到孔中。还表明阳离子葡聚糖可以选择性地吸附到不同位置，从而可以对多孔基材的表面与整体进行独特处理。
