Role of architecture and molecular weight in the formation of tailor-made ultrathin multilayers using dendritic macromolecules and click chemistry.
The high efficiency and mild reaction conditions associated with the Cu(I) catalyzed cycloaddition of azides and alkynes were exploited for the covalent layer-by-layer synthesis of dendritic thin films on silicon wafers. The preparation of azide and alkyne-terminated dendrimers based on bisMPA was accomplished by a divergent strategy; combinations of these monodisperse building blocks from the 2nd to the 5th generation were used for construction of the thin films. The layer-by-layer self assembly process proceeds under ambient conditions and was monitored by ellipsometry, XPS, and ATR-IR, which showed extremely regular growth of the dendritic thin films. Film thickness could be accurately controlled by both the size/generation number of the dendrimers as well as the number of layers. In comparison with linear analogues, the growth of the dendritic films was significantly more controlled and defect-free with each layer being thinner than the corresponding films prepared from the isomeric linear polymers, demonstrating the well-defined, three-dimensional nature of the dendritic architecture.