Structure and dynamic process of two-dimensional monodendron assembly

The formation and structure of self-assembled monolayers of three monodendrons, 5-(benzyloxy)-isophthalic acid derivatives, bearing different alkyl substitutents on highly oriented pyrolytic graphite have been studied by scanning tunneling microscopy (STM). It is found that the arrangements of the molecules with one and two alkyl substituents are different, although the two molecules both form long-range ordered structures. For the derivative with three alkyl substituents, no ordered arrangement in a large area was observed. The interaction mechanism of the self-assembly monolayer is discussed. As an example, the formation and dynamic process of the adlayer of monodendron derivative with one alkyl chain was directly investigated by STM. In the same scanning area, time-dependent disorder-order transition was observed. The result can be explained by the minimization of the free energy in the whole system.