Responsive and biodegradable hydrogels from radical ring-opening polymerisation of CKAs and their in-depth characterisation using advanced light scattering and fluorescence

自由基开环聚合（RROP）的环状烯酮缩酮（CKAs）已获得越来越多的关注，作为工具，以产生新的聚酯作为可生物降解的聚合物。该项目将看到它们扩展到聚合物网络中，以产生基于CKA 2-亚甲基-1，3，6-三氧杂环辛烷（MTC）的亲水性聚酯的pH响应和完全生物降解的水凝胶。鉴于我们最近报道的含胺CKA，其产生pH敏感的聚酯，pH敏感的水凝胶现在可以用RROP实现。为了评估基于RROP的水凝胶的全部范围，我们将评估不含胺的bis-CKA、新的带有胺的bis-CKA以及甲基丙烯酸交联剂。后者将是评估基于CKA的交联剂质量的重要基准物质。在该项目的过程中，将合成各种pH响应和非响应水凝胶，这是我们在水凝胶领域建立RROP的努力的基础。合成后，将使用最先进的动态和静态光散射技术对凝胶进行彻底表征。连同流变学和基于荧光的分析，网格大小，在微米和纳米尺度上的不均匀性以及客体物质在水凝胶内的扩散行为将被评估。不均匀性将产生对交联剂的反应性的洞察，以提供对合成努力的直接反馈，从而优化合成策略。与荧光方法一起评估扩散特性，将深入分析凝胶的pH响应行为及其微观和宏观变化。还将使用流变学和光散射来确认聚酯凝胶在环境条件下的稳定性。在对水凝胶进行全面分析之后，它们将经历由添加酯酶引发的完全降解。将使用与完整水凝胶相似的一系列方法监测降解，以了解降解期间凝胶的微观和宏观变化。降解过程中的流变学评估将允许确定凝胶点何时被破坏以及凝胶何时被破坏。然而，降解将进一步继续，直到没有寡聚残基留下。将对最终小分子进行分析，以确认完全降解，并确认最终羟基酸的预期结构。总而言之，该项目将引入一系列基于RROP的水凝胶，使用流变学，光散射和荧光方法对其进行全面分析，然后进行降解。这将是深入了解RROP并在聚合物化学领域进一步建立RROP的关键。

Radical Ring-Opening Polymerisation (RROP) of cyclic ketene actals (CKAs) has gained increasing attention as tool to generate novel polyesters as biodegradable polymers. This project will see their expansion into polymer networks to generate pH-responsive and fully biodegradable hydrogels based on the hydrophilic polyester from the CKA 2-methylene-1,3,6-trioxocane (MTC). In light of our recently reported amine-bearing CKA, which produces pH sensitive polyesters, pH-sensitive hydrogels are now in reach with RROP. In order to assess the full scope of RROP-based hydrogels, we will assess a bis-CKA without amines, a new amine-bearing bis-CKA as well as a methacrylic cross-linker. The latter will be an important benchmark substance to assess the quality of the CKA-based cross-linkers. A broad range of pH responsive and non-responsive hydrogels will be synthesised over the course of the project, underlying our efforts to establish RROP in the field of hydrogels. Following their synthesis, the gels will be thoroughly characterised using state-of-the-art dynamic and static light scattering techniques. Together with rheology and fluorescence-based analysis, mesh-sizes, inhomogeneities on the micro- and nanoscale as well as the diffusion behaviour of guest substances within the hydrogel will be assessed. Inhomogeneities will yield insights into the reactivity of the cross-linkers to provide direct feedback to the synthetic efforts in order to optimise the synthetic strategy. Together with the fluorescence methods to assess diffusion properties, the pH responsive behaviour with its micro- and macroscopic changes of the gel will be analysed in-depth. Rheology and light scattering will also be used to confirm the stability of the polyester-gels at ambient conditions. Following this full-scale analysis of the hydrogels, they will undergo a complete degradation triggered by the addition of esterase. Degradation will be monitored using a similar array of methods as the intact hydrogels to get insights into the micro- and macroscopic changes of the gels during degradation. Rheological assessments during degradation will allow to determine when the gel point has been breached and the gels have been destroyed. However, degradation will continue further until no oligomeric residues are left over. The final small molecules will be analysed to confirm a complete degradation but also to confirm the expected structure of the final hydroxy-acids. Altogether, this project will see the introduction of a broad array of hydrogels based on RROP, their full-scale analysis using rheology, light scattering and fluorescence methods, followed by their degradation. This will be key to get a deeper understanding of RROP and to establish it further in the field of polymer chemistry.