Covalent layer-by-layer (LbL) assembly is a powerful method used to construct functional ultrathin films that enables nanoscopic structural precision, componential diversity, and flexible design. Compared with conventional LbL films built using multiple noncovalent interactions, LbL films prepared using covalent crosslinking offer the following distinctive characteristics: (i) enhanced film endurance or rigidity; (ii) improved componential diversity when uncharged species or small molecules are stably built into the films by forming covalent bonds; and (iii) increased structural diversity when covalent crosslinking is employed in componential, spacial, or temporal (labile bonds) selective manners. In this review, we document the chemical methods used to build covalent LbL films as well as the film properties and applications achievable using various film design strategies. We expect to translate the achievement in the discipline of chemistry (film-building methods) into readily available techniques for materials engineers and thus provide diverse functional material design protocols to address the energy, biomedical, and environmental challenges faced by the entire scientific community.

中文翻译：

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共价逐层薄膜：化学，设计和多学科应用

共价逐层（LbL）组装是一种用于构建功能性超薄膜的有力方法，该薄膜可实现纳米级的结构精度，组件多样性和灵活的设计。与使用多种非共价相互作用构建的常规LbL薄膜相比，使用共价交联制备的LbL薄膜具有以下鲜明的特征：（i）增强的薄膜耐久性或刚度；（ii）当通过形成共价键将不带电荷的物种或小分子稳定地内置于膜中时，改善了组分多样性；（iii）当以部分，空间或时间（不稳定键）选择性方式使用共价交联时，结构多样性增加。在这篇评论中，我们记录了用于构建共价LbL膜的化学方法，以及使用各种膜设计策略可实现的膜性能和应用。我们希望将化学（成膜方法）学科的成就转化为材料工程师可以轻松获得的技术，从而提供多样化的功能材料设计方案，以解决整个科学界面临的能源，生物医学和环境挑战。