Dopamine (DA) surface chemistry has received significant attention because of its applicability in a wide range of research fields and the ability to graft functional molecules onto numerous solid surfaces. Various DA derivatives have been newly synthesized to identify key factors affecting the coating efficiency and to advance the coating system development. The oxidation of catechol into quinone followed by internal cyclization via the nucleophilic attack of primary amine is crucial for DA-based surface coating. Thus, it is expected that the amine group’s nucleophilicity control directly affects the coating efficiency. However, it has not been systematically investigated, and most studies have been conducted with the focus on the transformation of amines into amides, despite such approaches decreasing the coating efficiency; the nitrogen in amides is less nucleophilic than that in free amines. In this study, we investigated the effect of N-alkylation on dopamine surface chemistry. N,N-Dimethyldopamine (DMDA) was newly synthesized, and the coating efficiency was systematically compared with DA and N-methyldopamine (MDA). DA N-monomethylation improved the coating rate by increasing the nitrogen nucleophilicity, whereas N,N-dimethylation dramatically decreased the DA surface coating property. In addition, MDA remained capable of universal surface coating and secondary reactions using the surface catechols. This study provides opportunities for developing coating materials with advanced functions and an improved coating rate.

中文翻译：

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N-甲基化对多巴胺表面化学的影响

多巴胺（DA）表面化学因其在广泛的研究领域中的适用性以及将功能分子接枝到众多固体表面上的能力而受到了极大的关注。新合成了各种 DA 衍生物，以确定影响涂层效率的关键因素并推进涂层系统的开发。儿茶酚氧化成醌，然后通过伯胺的亲核攻击进行内部环化对于 DA 基表面涂层至关重要。因此，预计胺基的亲核性控制直接影响涂层效率。然而，尚未对其进行系统研究，并且大多数研究都集中在将胺转化为酰胺，尽管这种方法会降低涂层效率；酰胺中的氮的亲核性低于游离胺中的氮。在这项研究中，我们研究了多巴胺表面化学上的N-烷基化。新合成了N,N-二甲基多巴胺（DMDA），并系统地比较了DA和N-甲基多巴胺（MDA）的包覆效率。DA N -单甲基化通过增加氮的亲核性来提高包覆率，而N , N -二甲基化显着降低了DA表面包覆性能。此外，MDA 仍然能够使用表面邻苯二酚进行通用表面涂层和二次反应。该研究为开发具有先进功能和提高涂层速率的涂层材料提供了机会。