Solid state structures in spin-coated assemblies of oligo(cyclohexylidene) oxime derivatives and (partly) saturated analogues: an atomic force microscopy study

Abstract The deposition mechanism of a series of oligo(cyclohexylidene) oximes and their (partly) saturated analogues is studied, using atomic force microscopy (AFM). Hydrophilic silicon wafers have been spin-coated with chloroform solutions of a number of compounds which are denoted as 1( n ) , with n =1 or 2 , and as 2 – 6 . The compounds 1(1) and 2 formed either micro-crystals or multilayer structures, depending on the amount dissolved in the spin-coating solution. Compounds 1(2) and 3 – 6 had a different deposition behavior. In the beginning of the deposition process, the films were not rigid enough to reveal structural characteristics with AFM. Under ambient conditions initially small crystals were formed which slowly grew to micro-meter-sized crystals. High-resolution AFM images of these micro-crystals revealed the molecular packing. Single-crystal X-ray data of 1(1) , 2 and 3 showed that the surface structure of the micro-crystals was consistent with that of a terminated bulk crystal. The relations between the molecular structure of the various compounds and the characteristic times for the nucleation, the crystallization and the ripening stages of the deposition process are qualitatively discussed. We compare the present results with structural and stability data of Langmuir monolayers, in cases where the latter are accessible.