Neff Petra A, Wunderlich Bernhard K, Klitzing Regine V, Bausch Andreas R
Lehrstuhl für Biophysik-E22, Technische Universität München, Germany, and Stranski-Laboratorium, Technische Universität Berlin, Germany.
Langmuir. 2007 Mar 27;23(7):4048-52. doi: 10.1021/la063632t. Epub 2007 Feb 22.
The formation of polyelectrolyte multilayers (PEMs) is investigated using a silicon-on-insulator based thin film resistor which is sensitive to variations of the surface potential. The buildup of the PEMs at the silicon oxide surface of the device can be observed in real time as defined potential shifts. The influence of polymer charge density is studied using the strong polyanion poly(styrene sulfonate), PSS, combined with the statistical copolymer poly(diallyl-dimethyl-ammoniumchloride-stat-N-methyl-N-vinylacetamide), P(DADMAC-stat-NMVA), at various degrees of charge (DC). The multilayer formation stops after a few deposition steps for a DC below 75%. We show that the threshold of surface charge compensation corresponds to the threshold of multilayer formation. However, no reversion of the preceding surface charge was observed. Screening of polyelectrolyte charges by mobile ions within the polymer film leads to a decrease of the potential shifts with the number of layers deposited. This decrease is much slower for PEMs consisting of P(DADMAC-stat-NMVA) and PSS as compared to PEMs consisting of poly(allylamine-hydrochloride), PAH, and PSS. From this, significant differences in the dielectric constants of the polyelectrolyte films and in the concentration of mobile ions within the films can be derived.
使用基于绝缘体上硅的薄膜电阻器研究聚电解质多层膜（PEMs）的形成，该电阻器对表面电位的变化敏感。随着定义的电位偏移，可以实时观察到器件氧化硅表面上PEMs的形成。使用强聚阴离子聚苯乙烯磺酸盐（PSS）与统计共聚物聚（二烯丙基二甲基氯化铵-stat-N-甲基-N-乙烯基乙酰胺）（P（DADMAC-stat-NMVA））在不同电荷程度（DC）下研究聚合物电荷密度的影响。对于低于75%的DC，在几个沉积步骤后多层形成停止。我们表明表面电荷补偿的阈值对应于多层形成的阈值。然而，未观察到先前表面电荷的反转。聚合物膜内移动离子对聚电解质电荷的屏蔽导致电位偏移随沉积层数的增加而减小。与由聚（烯丙胺盐酸盐）（PAH）和PSS组成的PEMs相比，由P（DADMAC-stat-NMVA）和PSS组成的PEMs这种减小要慢得多。由此，可以得出聚电解质膜介电常数和膜内移动离子浓度的显著差异。
