HIGH-RESOLUTION IMAGING OF N-ALKANE CRYSTALS BY ATOMIC-FORCE MICROSCOPY

X-ray and electron crystallography of polymethylene chain compounds ar e known to be hindered by the very strong scattering from a dominant s ublattice, and the use of high-resolution electron microscopy is sever ely limited by radiation damage. This study shows that these problems may be overcome by using high-resolution atomic force microscopy (AFM) imaging. The work was performed on four types of linear alkane crysta l, namely n-C26H54, n-C30H62, n-C36H74 and n-C44H90, of different mole cular lengths. They were prepared by vapour deposition and from soluti on and deposited on mica and on highly oriented pyrolytic graphite. Th e results show that firstly AFM may complement, at a molecular and a s ubmolecular level, the data provided by X-ray and electron crystallogr aphy, secondly alkane crystals may be prepared with different orientat ions and the type of substrate has no influence, and thirdly AFM may b e used to induce orientational and conformational changes.