Covalent molecular assembly: Construction of ultrathin multilayer films by a two-dimensional fabrication method

► Ultrathin films were fabricated layer-wise by vertical and lateral assembly. ► Intra and interlayer covalent bonding were used to cross-link the molecular layers. ► Films with lateral cross-links, random cross-links, and linear links were fabricated. ► Laterally cross-linked films showed best resistance to harsh environments. ► The method developed can be used to build complex, robust nanostructures.