Rheological Control of Microemulsions via Multifunctional Thermoresponsive Polymer Surfactants

该项目的目的是通过添加新型两亲性热敏聚合物来控制微乳液的流变性能。为了实现粘度随温度升高的可控增长，我们将设计具有片段的共聚物，显示从亲水到疏水行为的LCST转变，然后在介观水平上诱导结构重组。通过系统地改变热响应块的类型、数量和位置，我们将获得量身定制的聚合物结构，以诱导微乳液/聚合物混合体系的复杂结构和流变行为随温度的变化。另一个主要目的是获得对结构相互作用机制的透彻理解。聚合物表面活性剂将通过控制自由基聚合来合成，这允许非常可变的方法来获得这种定义良好的聚合物结构。然后这些将被纳入生物相容性微乳液中，形成的结构将通过静态和动态光散射以及小角度中子散射（SANS）作为温度的函数进行全面研究，其中SANS将通过对比度变化产生详细的结构信息。这将成为低温透射电子显微镜（cryo-TEM）的重要补充，用于全面的介观结构表征。此外，荧光测量将产生关于形成的网络的连通性的信息。同时，这些网络系统将在整个相关温度范围内通过流变学进行全面研究。特别有趣和具有挑战性的将是合成和研究具有两种不同LCST块的聚合物。它们应表现出特别复杂的聚集行为（以混合或分离的疏水域作为交联点），并具有相应的流变特性。然后，我们的目标是推导出不同聚合物/微乳液杂化体系中聚合物表面活性剂的分子结构、可切换交联聚集体的介观结构、微乳液的结构和浓度以及由此产生的宏观流变性能之间的详细相关性。这样的系统不仅具有基础的科学兴趣，而且在应用方面也非常有趣，例如在制药或化妆品中，特别是当微乳液的高溶解能力与高粘度甚至凝胶状行为相结合时。

Aim of the project is the temperature control of the rheological properties of microemulsions by the addition of novel amphiphilic thermoresponsive polymers. In order to achieve a controlled viscosity increase with increasing temperature we will design copolymers with segments, that show an LCST transition from hydrophilic to hydrophobic behaviour, which then induces a structural reorganisation on the mesoscopic level. Via a systematic variation of type, number and position of the thermoresponsive blocks we will obtain tailor-made polymer architectures in order to induce a controlled complex structural and rheological behaviour of the microemulsion/polymer hybrid systems as a function of temperature. The other main aim is to gain a thorough understanding of the mechanism of the structural interaction. The polymer surfactants will be synthesized by controlled radical polymerisation, which allows for a very variable approach to such well-defined polymer structures. These will then become incorporated into biocompatible microemulsions and the formed structures will become studied as a function of temperature comprehensively by means of static and dynamic light scattering as well as small-angle neutron scattering (SANS), where SANS will yield detailed structural information by using contrast variation. This will become importantly complemented by cryogenic-transmission electron microscopy (cryo-TEM) for a comprehensive mesoscopic structural characterisation. In addition, fluorescence measurements will yield information regarding the connectivity of the formed network. In parallel, these network systems will be investigated comprehensively by rheology over the whole relevant temperature range. Particularly interesting and challenging will be synthesis and investigation of polymers with two different LCST blocks. They shall exhibit a particularly complex aggregation behaviour (with mixed or separated hydrophobic domains as cross-linking points) with corresponding rheological properties. Our aim then is to derive for the different polymer/microemulsion hybrid systems detailed correlations between the molecular structure of the polymer surfactants, the mesoscopic structure of the switchably cross-linked aggregates, the structure and concentration of the microemulsion and the resulting macroscopic rheological properties. Such systems are not only of fundamental scientific interest but also highly interesting for applications, e g. in pharmacy or cosmetics, especially when the high solubilisation capacity of microemulsions is to be combined with high viscosity or even gel-like behaviour.