Department of Chemistry, Surface and Corrosion Science, Royal Institute of Technology, Drottning Kristinas väg 51, SE-100 44 Stockholm, Sweden.
Langmuir. 2011 Feb 1;27(3):1044-50. doi: 10.1021/la103957v. Epub 2011 Jan 5.
Adsorption properties of stoichiometric and nonstoichiometric polyelectrolyte complexes (PECs) have been investigated by means of dual polarization interferometry (DPI) and X-ray photoelectron spectroscopy (XPS). Poly(sodium styrenesulfonate) (NaPSS) of molecular weight 4300 g/mol was used as polyanion, and two bottle-brush copolymers possessing different molar ratios of the cationic segment methacryloxyethyltrimethylammonium chloride (METAC) and the nonionic segment poly(ethylene oxide) methyl ether methacrylate (PEO(45)MEMA) were used as polycations. They are referred to as PEO(45)MEMA:METAC-25 and PEO(45)MEMA:METAC-50, where the last digits denote the mol % of charged main-chain segments. The time evolution of the adsorbed amount, thickness, and refractive index of the PEC layers were determined in aqueous solution using DPI. We demonstrate that cationic, uncharged, and negatively charged complexes adsorb to negatively charged silicon oxynitride and that maximum adsorption is achieved when small amounts of PSS are present in the complexes. The surface composition of the adsorbed PEC layers was estimated from XPS measurements that demonstrated very low content of NaPSS. On the basis of these data, the PEC adsorption mechanism is discussed and the competition between PSS and negative surface sites for association with the cationic polyelectrolyte is identified as a key issue.
通过双折射干涉法（DPI）和 X 射线光电子能谱法（XPS）研究了化学计量和非化学计量聚电解质复合物（PEC）的吸附性能。分子量为 4300 g/mol 的聚（苯乙烯磺酸钠）（NaPSS）用作聚阴离子，两种梳型共聚物具有不同摩尔比的阳离子段甲基丙烯氧基乙基三甲基氯化铵（METAC）和非离子段聚（氧化乙烯）甲基醚甲基丙烯酸酯（PEO(45)MEMA）用作聚阳离子。它们分别称为 PEO(45)MEMA:METAC-25 和 PEO(45)MEMA:METAC-50，最后一位数字表示带电荷主链段的摩尔%。使用 DPI 在水溶液中确定了 PEC 层的吸附量、厚度和折射率的时间演变。我们证明了带正电荷、不带电和带负电荷的复合物会吸附到带负电荷的硅氧氮化物上，并且当复合物中存在少量 PSS 时会达到最大吸附量。通过 XPS 测量估计了吸附的 PEC 层的表面组成，结果表明 PSS 的含量非常低。基于这些数据，讨论了 PEC 吸附机制，并确定了 PSS 与带负电荷的表面位点与阳离子聚电解质缔合的竞争是一个关键问题。
