Köhler Karen, Shchukin Dmitry G, Möhwald Helmuth, Sukhorukov Gleb B
Max-Planck-Institute of Colloids and Interfaces, 14424 Potsdam, Germany.
J Phys Chem B. 2005 Oct 6;109(39):18250-9. doi: 10.1021/jp052208i.
The temperature-dependent behavior of hollow polyelectrolyte multilayer capsules consisting of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(styrene sulfonate) (PSS) with a different number of layers was investigated in aqueous media using confocal laser scanning microscopy, scanning and transmission electron microscopy, atomic force microscopy, and elemental analysis. Capsules with an even number of layers exhibited a pronounced shrinking at elevated temperature resulting in a transition to a dense sphere, whereas capsules with an odd number of layers swelled during heating to 5-fold of their initial size followed by their rupture. This effect increases for odd layer numbers and decreases for even layer numbers with increasing layer number. According to elemental analysis, an excess of PDADMAC monomers exists within the multilayers of capsules with an odd number of layers leading to a repulsion between the positive charges, whereas shells with an even number of layers have a balanced ratio between the oppositely charged polyions, so that the temperature-dependent behavior is controlled by the different interactions between polyelectrolytes and the bulk water. At a certain temperature, the polyelectrolyte material softens thus facilitating any rearrangement. Besides incubation temperature, the duration of heating has an influence on the restructuring of the multilayers.
采用共聚焦激光扫描显微镜、扫描电子显微镜、透射电子显微镜、原子力显微镜和元素分析等方法，研究了由不同层数的聚二烯丙基二甲基氯化铵（PDADMAC）和聚苯乙烯磺酸盐（PSS）组成的中空聚电解质多层胶囊在水性介质中的温度依赖性行为。偶数层的胶囊在温度升高时表现出明显的收缩，导致转变为致密球体，而奇数层的胶囊在加热过程中膨胀至初始尺寸的5倍，随后破裂。随着层数增加，这种效应在奇数层数时增强，在偶数层数时减弱。元素分析表明，奇数层胶囊的多层结构中存在过量的PDADMAC单体，导致正电荷之间相互排斥，而偶数层的壳层中带相反电荷的聚离子比例平衡，因此温度依赖性行为受聚电解质与大量水之间不同相互作用的控制。在一定温度下，聚电解质材料变软，从而有利于任何重排。除了孵育温度外，加热时间对多层结构的重组也有影响。
