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Molecular structure and dynamics in monolayers of long chain alkanes and alkyl‐derivatives
Author(s) -
Rabe Jürgen P.,
Buchholz Stefan
Publication year - 1991
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19910500125
Subject(s) - alkyl , monolayer , graphite , alkane , chemistry , crystallography , scanning tunneling microscope , lattice (music) , perpendicular , stereochemistry , chemical physics , materials science , hydrocarbon , organic chemistry , geometry , nanotechnology , physics , biochemistry , acoustics , mathematics
Long chain alkanes (C 34 H 70 and C 50 H 102 ), a fatty acid (C 17 H 35 COOH) and an alkyl‐substituted triiodobenzoate (I 3 H 2 C 6 COOC 18 H 37 ) have been adsorbed at the interface between organic solutions and the basal plane of graphite. In‐situ scanning tunneling microscopy (STM) has been employed to investigate their structure and dynamics on the scale of 10 pm and 1 ms or longer. All adsorbates form two‐dimensional polycrystals. The molecules tend to organize in lamellae with the extended alkyl chains oriented parallel to a lattice axis within the basal plane of graphite. The n‐alkane chains pack in a lattice commensurate with the graphite lattice and the carbon skeleton planes approximately perpendicular to the substrate. Due to the additional space required by a carboxyl end group the alkyl lattice in the fatty acid is incommensurate with the substrate and the carbon skeleton planes lie approximately parallel to the surface. In the triiodobenzoate the headgroup takes the space of about two alkyl chains resulting in an interdigitated packing.