Coupled measurement system for investigation of adsorption and complexing behaviour of polymers and nanoparticles in mortar and concrete: FFF-MALS-ICP-MS

现代水泥基粘结剂体系是以多组分组成为特征的高性能材料。在硬化过程中，许多反应同时发生，如溶解、成核和生长以及溶胶-凝胶反应。有机掺合料的部分未知结构、整个体系的复杂组成以及早期反应产物的尺寸很小，使得研究水泥水化早期阶段的过程变得困难。魏玛包豪斯大学的F.A.Finger研究所(FIB)几十年来一直在国际层面上研究这些过程。应用一种耦合测量系统，能够分别表征不同结构、组成和电荷的离子、聚合物、络合物、纳米粒子和微粒。该系统由分馏模块和检测模块组成。分离模块由基本的高效液相色谱泵和自动进样器、可由GPC/SEC柱替代的非对称流量场流分离通道(AF4通道)和带电场的AF4通道组成。分离发生在明渠(AF4)中，不对称的流型取决于颗粒的流体动力学半径，因此小半径的颗粒比大半径的颗粒更早洗脱。如果在流体动力学流型上另外施加电场，则根据颗粒的电泳迁移率来分离颗粒。Zeta电位可以通过比较两个色谱图(分别是AF4和电AF4)来计算。如果必须测定纯聚合物的分子质量，可以用GPC/SEC柱取代AF4通道。检测模块由多角度激光散射检测器(MALS)、动态光散射检测器(DLS)、折射率检测器(RI)和电感耦合等离子体质谱仪(ICPMS)组成。MALS用于确定粒子的回转半径，可用于计算聚合物的相对分子质量。与静态光散射相结合，流体动力学半径提供了有关聚合物构象及其二级结构的重要信息。特殊的RI检测器是一种高度浓度灵敏的检测器，用于定量溶液中的聚合物。具有低检测下限和高检测速度的在线耦合的电感耦合等离子体质谱提供了有关颗粒化学成分的信息。通过对许多质量示踪的瞬时记录，应该能够区分颗粒的有机和无机性质。应用耦合测量系统集成到F.A.Finger建筑材料研究所的化学分析实验室，由建筑化学和聚合物材料主席(Osburg教授)和建筑材料科学主席(Ludwig教授)操作。

Modern cement-based binder systems are high-performance materials that are characterized by a multi-component composition. During the hardening process many reactions occur simultaneously, for instance solution, nucleation and growth as well as sol-gel reactions. The partially unknown structure of organic admixtures, the complex composition of the entire system and the very small dimensions of the early reaction products make it difficult to study the processes in the early phase of cement hydration. The F.A. Finger Institut für Baustoffkunde (FIB) at the Bauhaus Universität Weimar has been researching these processes on an international level for decades. A coupled measurement system is applied for which is capable of characterizing ions, polymers, complexes, nanoparticles and microparticles of different structure, composition and charge respectively. The system consists of a fractionation module and a detection module. The fractionation module consists of the basic HPLC components pump and autosampler, an asymmetric flux-field flow fractionation channel (AF4 channel) which can be replaced by a GPC/SEC column as well as an AF4 channel with electric field. The separation takes place in an open channel (AF4) with an asymmetrical flow profile depending on the hydrodynamic radii of the particles, whereby particles with small radii elute earlier than larger ones. If an electric field is additionally applied to the hydrodynamic flow profile, the particles are separated according to their electrophoretic mobility. The zeta potential can be calculated by comparing both chromatograms (AF4 and electric-AF4 respectively). The AF4 channel could be replaced by a GPC/SEC column if the molecular mass of pure polymers has to be determined. The detection module consists of a multi-angle laser scattering detector (MALS), a dynamic light scattering detector (DLS), a refractive index detector (RI) and an inductively coupled plasma mass spectrometer (ICP-MS). The MALS is used to determine the gyration radii of the particles, which can be used to calculate the molecular weight of polymers. In combination with static light scattering, the hydrodynamic radius provides important information about the conformation of the polymer and its secondary structure. The special RI detector is a highly concentration-sensitive detector used for quantification of polymers in solution. An inline-coupled ICP-MS possessing low detection limits and high detection speed provides information on the chemical composition of the particles. The transient recording of many mass traces should make it possible to distinguish between the organic and inorganic nature of the particles. The applied coupled measuring system is integrated into the chemical analysis laboratory of the F.A. Finger Institute of building materials and is operated by the Chair of Building Chemistry and Polymer Materials (Prof. Osburg) as well as the Chair of Construction Material Science (Prof. Ludwig).