Rheology and structural properties of protein and particle-stabilized foams - a multi-scale approach

该项目旨在更深入地了解和更好地控制蛋白质和颗粒稳定泡沫的流变学和结构特性。因此，必须在不同的长度尺度上研究结构与动力学之间的关系。我们希望采用一种多尺度的方法，包括宏观泡沫、单泡沫膜/片层以及液体/空气界面。这一战略需要不同的科学和技术技能，而不是单个研究小组所涵盖的。Willenbacher小组（机械过程工程）在泡沫和界面流变学方面贡献了专业知识。m<s:1> ller- buschbaum小组（物理学）将使用各种散射技术来探索吸附的两亲性表面层的结构。v. Klitzing组（物理化学）在表征泡沫膜中的相互作用和界面吸收现象方面有着丰富的经验。屈服应力和剪切模量是表征泡沫材料流变特性的重要参数。对牛奶蛋白泡沫的初步研究表明，这些物理参数与相应蛋白溶液的界面弹性性能直接相关。但在一定的物理化学条件下，泡沫流变性和界面弹性之间的这些简单相关性出现了剧烈的偏差，这可能是由于连接相邻表面层的泡沫膜内部的聚集和结构形成所致。基于这些发现，提议的项目有两个目标：1。我们想评估在牛奶蛋白中发现的屈服应力与泡沫模量以及相应溶液的界面弹性之间的简单关系是否也适用于其他体系。不同的蛋白质和纳米颗粒将用于泡沫稳定。在此基础上，建立了泡沫流变参数与相应溶液界面弹性的预测物理模型。在一定的物理化学条件下（pH、离子强度和价），上述界面与泡沫流变的关系失效。表面活性成分在液/气界面和泡沫片层内的聚集和结构形成将被研究。镜面反射和掠入射x射线和中子反射将用于阐明表层的横向和垂直组成（长度尺度：1-100 nm）。在微米长度尺度上，表层的横向非均质性将从示踪粒子的热扩散系数的变化中推断出来。此外，将利用薄膜压力平衡技术探讨泡沫膜稳定性方面的聚集和结构形成。排水过程中的结构研究将揭示泡沫片层排水结构形成的特征状态。

The project aims at a deeper understanding and a better control of rheology and structural properties of protein and particle-stabilized foams. Therefore, the correlation between structure and dynamics has to be investigated on different length scales. We want to employ a multi-scale approach comprising the macroscopic foam, single foam films/ lamellae as well as the liquid/air interface. This strategy requires different scientific and technical skills not covered by an individual research group. The Willenbacher group (mechanical process engineering) contributes its expertise regarding rheology of foams and interfaces. The Müller-Buschbaum group (physics) will use various scattering techniques to explore the structure of the adsorbed amphiphilic surface layer. The v. Klitzing group (physical chemistry) has profound experience in characterizing interactions in foam films and interfacial absorption phenomena.Yield stress and shear modulus are crucial parameters characterizing rheological properties of foams. Preliminary work on milk protein foams disclosed that these physical parameters are directly related to interfacial elastic properties of the corresponding protein solutions. But under certain physico-chemical conditions drastic deviations from these simple correlations between foam rheology and interfacial elasticity were found presumably due to aggregation and structure formation within foam films interconnecting adjacent surface layers. Based on these findings the proposed project has two goals:1. We want to evaluate whether the simple relationship between yield stress and modulus of foams and interfacial elasticity of corresponding solutions found for milk proteins is also valid for other systems. Different proteins and nanoparticles will be used for foam stabilization. Based on these data a predictive physical model relating foam rheological parameters and interfacial elasticity of corresponding solutions will be developed.2. Under certain physico-chemical conditions (pH, ionic strength and valency) the above mentioned relationship between interfacial and foam rheology fails. Aggregation and structure formation of surface active ingredients at the liquid/ air interface and within foam lamellae will be investigated.Specular and grazing incidence X-ray and neutron reflection will be used to elucidate the lateral and vertical composition of the surface layer (length scale: 1-100 nm). Lateral heterogeneities of the surface layer on a micrometer length scale will be deduced from variations in the thermal diffusivity of tracer particles. Furthermore, aggregation and structure formation will be explored with respect to foam film stability using the Thin Film Pressure Balance technique. Structural investigations during drainage will reveal how and at which characteristic state of drainage structure formation across foam lamellae takes place.