Oriented growth of n-alkanes crystals on nanostructured poly(tetrafluoroethylene) substrates

The growth of n-alkane (CnH2n+2) crystals on poly(tetrafluoroethylene) subs trates (PIA) obtained by the friction-transfer method was studied by optica l microscopy and grazing incidence x-ray diffraction. The experiments perfo rmed on a series of molecules ranging from n=21 to n=33 reveal the existenc e of a preferred contact plane with the PIA substrate corresponding to a mi nimum in lattice mismatch between the two crystallographic systems. Indepen dently of the chain length, the n-alkane crystals tend to orient with their (200) planes parallel to the substrate, the molecular axis being preferent ially aligned along the friction direction of the PTFE substrate. In our st udy, we demonstrate that the pathways (i.e., the orientation mechanisms) st rongly influence the observed morphology in the low temperature phase. (C) 2001 American Institute of Physics.