Adamczyk Zbigniew, Michna Aneta, Szaraniec Magdalena, Bratek Anna, Barbasz Jakub
Institute of Catalysis and Surface Chemistry, Polish Academy of Science, Niezapominajek 8, 30-239 Cracow, Poland.
J Colloid Interface Sci. 2007 Sep 1;313(1):86-96. doi: 10.1016/j.jcis.2007.04.005. Epub 2007 May 22.
Deposition kinetics of polystyrene latex (averaged particle size of 0.66 microm) on mica covered by poly(ethylene imine) (PEI), a cationic polyelectrolyte having an average molecular mass of 75,000 g mol(-1), was studied using the impinging-jet method. The hydrodynamic radius of PEI, determined by PCS measurements, was 5.3 nm. The electrophoretic mobility of PEI was measured as a function of pH for ionic strengths of 10(-3) and 10 (-2) M, which made it possible one to determine the amount of electrokinetic charge of the molecule and its zeta potential. Formation of the polyelectrolyte layer on mica was followed by measuring the streaming potential in the parallel-plate channel. From these measurements, the dependence of the apparent zeta potential of mica on the surface coverage of PEI was determined. The amount of adsorbed PEI on mica was calculated from the convective diffusion theory. These results were quantitatively interpreted in terms of the theoretical model postulating a particle-like adsorption mechanism for PEI with not too significant shape deformation upon adsorption. On the other hand, the Gouy-Chapman model postulating the adsorption in the form of flat disks was proved inappropriate. After the surface was fully characterized, particle deposition experiments were carried out with the aim of finding the correlation between the polymer coverage and the initial rate of latex particle deposition. In the range of small polyelectrolyte coverage, a monotonic relation between the polymer coverage and the initial deposition rate of particles, as well as the jamming coverage, was found. For Theta(PEI)>0.25, the initial particle deposition rate attained the value predicted from the convective diffusion theory for homogeneous surfaces. These results were interpreted theoretically by postulating that an effective immobilization of colloid particles occurred on local polyelectrolyte assemblages containing between two and three PEI molecules.
采用冲击射流法研究了聚苯乙烯胶乳（平均粒径0.66微米）在覆盖有聚（乙烯亚胺）（PEI）的云母上的沉积动力学，PEI是一种平均分子量为75,000 g mol(-1)的阳离子聚电解质。通过PCS测量确定的PEI的流体动力学半径为5.3纳米。测量了PEI在10(-3)和10 (-2) M离子强度下的电泳迁移率随pH的变化，这使得能够确定分子的电动电荷量及其zeta电位。通过测量平行板通道中的流动电位来跟踪云母上聚电解质层的形成。从这些测量中，确定了云母的表观zeta电位对PEI表面覆盖率的依赖性。根据对流扩散理论计算了云母上吸附的PEI的量。这些结果根据假设PEI具有颗粒状吸附机制且吸附时形状变形不太明显的理论模型进行了定量解释。另一方面，假设以扁平圆盘形式吸附的古依-查普曼模型被证明是不合适的。在对表面进行充分表征后，进行了颗粒沉积实验，目的是找出聚合物覆盖率与胶乳颗粒初始沉积速率之间的相关性。在小聚电解质覆盖率范围内，发现了聚合物覆盖率与颗粒初始沉积速率以及堵塞覆盖率之间的单调关系。对于Theta(PEI)>0.25，初始颗粒沉积速率达到了均匀表面对流扩散理论预测的值。这些结果通过假设在含有两到三个PEI分子的局部聚电解质聚集体上发生了胶体颗粒的有效固定而从理论上进行了解释。
