DFG-DST Project: Stimuli-Responsive Microgels with Permanent and Dynamic Ionic Crosslinks: Chemical Design and Behavior in Aqueous Solutions

在这个项目中，我们建议设计一个两性离子构建块的分子工具箱，并制定新的合成方案，以获得具有控制分布和高负载两性离子基团的微凝胶。对于这些两性离子微凝胶，我们将对其分子结构与水溶液中刺激响应行为之间的关系进行全面的研究。我们的目标是合成具有精确控制分子结构（两性离子基团的化学结构）和可调尺寸（单体与大单体）的两性离子反应构建块。我们将使用不同的聚合方法合成基于n -乙烯基己内酰胺（VCL）、n -乙烯基胡椒酮（VPP）和n -乙烯基吡啶酮（VPR）的温度响应微凝胶，这些微凝胶中两性离子基团的数量可调，分布可控（随机或核壳）。合成的微凝胶将表现出两个独特的特征：它们同时具有较高的临界溶液温度（UCST）（由于聚合物链中两性离子基团的存在）和较低的临界溶液温度（LCST）（由于聚合物链中内酰胺基团的存在）。它们也会有两种类型的交联，由两性离子基团产生的离子动态交联和由交联剂产生的共价交联。为了了解合成的两性离子微凝胶的性质，我们将使用不同的分析方法对其进行表征，以了解其在水溶液中的内部结构和行为。具体来说，我们将关注以下问题：-微凝胶中需要多少两性离子基团才能形成离子（动态）交联？两性离子构建单元（单体与大单体）的结构和聚合物链的两亲性（内酰胺环的大小）如何影响离子（动态）交联的形成？-能否调节两性离子基团含量高的微凝胶的体积相变温度（UCST和LCST）、膨胀度和胶体稳定性？该项目的科学成果将是设计一个具有共价和离子（动态）交联的温度响应两性离子微凝胶工具箱，并了解它们在水溶液中的行为。基于这些知识，将产生新的应用前景，这些微凝胶作为药物递送载体和自愈和蛋白质排斥涂层的构建块的候选物。

In this project we propose to design a molecular toolbox of zwitterionic building blocks and to elaborate new synthesis protocols to obtain microgels with a controlled distribution and a high loading of zwitterionic groups. For these zwitterionic microgels a comprehensive picture to show the relationship between the molecular structure and the stimuli-responsive behavior in aqueous solutions is going to be developed.We aim to synthesize zwitterionic reactive building blocks with precisely controlled molecular architecture (chemical structure of zwitterionic group) and tunable size (monomers vs. macromonomers). Using different polymerisation approaches we will synthesize temperature-responsive microgels based on N-vinylcaprolactam (VCL), N-vinylpiperidone (VPP) and N-vinylpyrolidone (VPR) with tunable amount and controlled distribution of zwitterionic groups in the microgels (random vs. core-shell). The synthesized microgels will exhibit two unique features: They will have both, an upper critical solution temperature (UCST) (due to the presence of zwitterionic groups in polymer chains) and a lower critical solution temperature (LCST) (due to the presence of lactam groups in polymer chains). They will also have two types of crosslinks, ionic dynamic crosslinks generated by zwitterionic groups and covalent crosslinks generated by a crosslinker.To understand the properties of the synthesized zwitterionic microgels we will perform their characterization using different analytical methods to understand the internal structure and behavior in aquous solutions. Specifically, we will focus on following questions:-Which amount of zwitterionic groups in the microgels is required for the formation of ionic (dynamic) crosslinks?;-How do the structure of the zwitterionic building blocks (monomers vs. macromonomers) and the amphiphilic properties of the polymer chains (size of the lactam rings) influence the formation of ionic (dynamic) crosslinks?; -Can we tune the volume phase transition temperatures (UCST and LCST), swelling degree and colloidal stability of the microgels with high contents of zwitterionic groups?The scientific outcome of this project will be an elaborated synthesis to design a toolbox of temperature-responsive zwitterionic microgels with covalent and ionic (dynamic) crosslinks and an understanding of their behavior in aqueous solutions. Based on this knowledge new application perspectives for such microgels, as candidates for drug delivery vehicles and building blocks for self-healing and protein-repelling coatings, will be generated.