Self-healing coatings by reversible crosslinking: Mechanistic investigations of defined model systems on the molecular level using linear and non-linear Raman microspectroscopy

聚合物涂层对每一个现代社会都是必不可少的，它可以保护无数产品的表面。自修复性能的引入将对这些材料的寿命产生重要影响。尽管第一个具有自我修复性能的商用涂层已经存在，但其潜在的分子过程仍远未被了解。该项目的中心目标是阐明依赖可逆交联链，特别是可逆Diels-Alder(DA)环加成反应的涂层自愈的潜在分子机制。在这个项目中，我们建议(I)使用一种含有双烯呋喃和亲双烯马来酰亚胺的新型聚合物，同时改变取代模式来调节愈合温度和愈合效率，以及(Ii)研究一种新型的杂化Diels-Alder反应(硫酮/二硫代酯与双烯)用于自我修复应用。这两种类型的交联体系将通过线性和非线性拉曼光谱结合二维相关分析进行详细的研究。对于自我修复系统，还没有描述这种方法；它将允许调查受损和非受损区域，因此可以区分两者。作为自我修复过程的触发器，主要将利用热量；将根据对基本原理和机制的尝试增加知识来研究其他激活剂。

Polymer coatings are essential for every modern society, protecting surfaces of an uncountable number of products. The introduction of self-healing properties would have an important impact on the lifetime of these materials. Even despite the fact that first commercial coatings with self-healing properties exist, the underlying molecular processes are far from being understood. The central target of the proposed project is the elucidation of the underlying molecular mechanisms of self-healing in coatings relying on reversible crosslinks, in particular on reversible Diels-Alder (DA) cycloadditions. In this project we propose (i) the usage of a new type of polymer containing both the diene furan and the dienophile maleimide, while varying the substitution pattern to tune the healing temperature as well as the healing efficiency, and (ii) the investigation of a new type of a hetero-Diels-Alder reactions (thioketones/dithioesters with dienes) for self-healing applications. Both types of crosslinked systems will be investigated in detail by linear and non-linear Raman microspectroscopy in combination with two-dimensional correlation analysis. For self-healing systems, such an approach has not yet been described; it will allow the investigation of damaged and non-damaged areas and, therefore, the differentiation between both. As a trigger for the self-healing process, primarily heat will be utilised; additional activators will be investigated based on the attempted increased knowledge of the basic principles and mechanisms.