SOLID-STATE STRUCTURES IN SPIN-COATED ASSEMBLIES OF OLIGO(CYCLOHEXYLIDENE) OXIME DERIVATIVES AND (PARTLY) SATURATED ANALOGS - AN ATOMIC-FORCE MICROSCOPY STUDY

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 wit h 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 eith er micro-crystals or multilayer structures, depending on the amount di ssolved in the spin-coating solution. Compounds 1(2) and 3-6 had a dif ferent 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 form ed which slowly grew to micro-meter-sized crystals. High-resolution AF M images of these micro-crystals revealed the molecular packing. Singl e-crystal X-ray data of 1(1), 2 and 3 showed that the surface structur e 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 crystal lization and the ripening stages of the deposition process are qualita tively discussed. We compare the present results with structural and s tability data of Langmuir monolayers, in cases where the latter are ac cessible. (C) 1998 Published by Elsevier Science B.V. All rights reser ved.