Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Cracow, Poland.
J Colloid Interface Sci. 2015 Jul 15;450:82-90. doi: 10.1016/j.jcis.2015.02.057. Epub 2015 Feb 28.
Monolayers of the cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDADMAC) on mica were thoroughly characterized using the streaming potential and the colloid deposition methods. Initially, the stability of the monolayers was determined by performing desorption experiments carried out under diffusion-controlled regime. It was shown that the desorption of the polyelectrolyte at the ionic strength range 0.01-0.15 M is negligible over the time of 20 h. The structure of PDADMAC monolayers and orientation of molecules were evaluated using the colloid deposition measurements involving negatively charged polystyrene latex microspheres, 820 nm in diameter. The functional relationships between the polyelectrolyte coverage and latex coverage deposited within 20 h were acquired by direct optical microscope. In this way the influence of ionic strength varied in the range 0.15-0.01 M on the molecule orientation in monolayers was determined. It was shown that for ionic strength of 0.15 M nearly one to one mapping of polyelectrolyte chains by colloid particles can be achieved for PDADMAC coverage below 0.1%. In this way, because of a considerable surface area ratio between the macromolecule and the colloid particle, an enhancement factor of 10(3) can be attained. This behavior was quantitatively interpreted in terms of the random site adsorption model whereas the classical mean-field theory proved inadequate. On the other hand, for lower ionic strength, it was confirmed that an irreversible immobilization of latex particles can only occur at a few closely spaced PDADMAC chains. It was shown that these experimental results were consistent with the side-on adsorption mechanisms of PDADMAC at mica for the above ionic strength.
采用流动电势和胶体沉积法对云母上的阳离子聚电解质聚二烯丙基二甲基氯化铵（PDADMAC）单层进行了彻底的表征。首先，通过在扩散控制条件下进行解吸实验来确定单层的稳定性。结果表明，在 0.01-0.15 M 的离子强度范围内，聚电解质在 20 h 内的解吸可以忽略不计。使用直径为 820nm 的带负电荷的聚苯乙烯乳胶微球进行胶体沉积测量，评估了 PDADMAC 单层的结构和分子取向。通过直接光学显微镜获得了在 20 h 内沉积的聚电解质覆盖率和乳胶覆盖率之间的功能关系。通过这种方式，确定了离子强度在 0.15-0.01 M 范围内对单层中分子取向的影响。结果表明，对于离子强度为 0.15 M，对于 PDADMAC 覆盖率低于 0.1%，可以通过胶体颗粒实现聚电解质链的近乎一对一映射。通过这种方式，由于大分子和胶体颗粒之间的表面积比相当大，可以达到 10(3) 的增强因子。这种行为可以根据随机位吸附模型进行定量解释，而经典的平均场理论证明是不够的。另一方面，对于较低的离子强度，仅在少数紧密间隔的 PDADMAC 链上才能确认乳胶颗粒的不可逆固定化。结果表明，这些实验结果与上述离子强度下 PDADMAC 在云母上的侧吸附机制一致。
