Published on Web 11/27/2003
Transfer of π-Conjugated Columnar Stacks from Solution to
Surfaces
Pascal Jonkheijm, Freek J. M. Hoeben, Ralf Kleppinger, Jeroen van Herrikhuyzen,
Albertus P. H. J. Schenning,* and E. W. Meijer*
Contribution from the Laboratory of Macromolecular and Organic Chemistry, EindhoVen
UniVersity of Technology, P.O. Box 513, 5600 MB EindhoVen, The Netherlands
Received September 3, 2003; E-mail: j.schenning@tue.nl; e.w.meijer@tue.nl
Abstract: Three hydrogen-bonded oligo(p-phenylenevinylene)s, OPV3, OPV4, and OPV5, that differ in
conjugation length have been synthesized and fully characterized. All three compounds contain chiral side
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chains, long aliphatic chains, and a ureido-s-triazine hydrogen bonding unit. H NMR and photophysical
measurements show that the OPV oligomers grow hierarchically in an apolar solvent; initially, dimers are
formed by hydrogen bonds that subsequently develop into stacks by π-π interactions of the phenylenevi-
nylene backbone with induced helicity via the chiral side chains. SANS measurements show that rigid
cylindrical objects are formed. Stacks of OPV4 have a persistence length of 150 nm and a diameter of 6
nm. OPV3 shows rigid columnar domains of 60 nm with a diameter of 5 nm. Temperature and concentration
variable measurements show that the stability of the stacks increases with the conjugation length as a
result of more favorable π-π interactions. The transfer of the single cylinders from solution to a solid support
as isolated objects is only possible when specific concentrations and specific solid supports are used as
investigated by AFM. At higher concentrations, an intertwined network is formed, while, at low concentration,
ill-defined globular objects are observed. Only in the case of inert substrates (graphite and silicium oxide)
single fibers are visible. In the case of the repulsive surfaces (mica and glass), clustering of the stacks
occurs, while, at attractive surfaces (gold), the stacks are destroyed.
Introduction
In optoelectronic materials science, the specific properties of
a device are likewise determined by the chemical structure and
Noncovalent interactions of molecular building blocks into
supramolecular structures is a fundamental building principle
for biological materials and found in various systems ranging
from double stranded DNA to complex structures such as
Tobacco Mosaic Virus.1 The appeal that nature holds lies in
the fact that the information at the molecular level guides the
organization at the supramolecular level. This intelligent
engineering of molecules has inspired many research groups to
direct disordered molecules via molecular recognition into well-
organized self-assembled structures with a specific function.2
A manifold of examples exist in which different types of
noncovalent interactions are applied to construct complex
architectures adopting stable and compact conformations which
may find applications in the field of biology and materials
science.3 An emerging challenge for applying these supramo-
lecular architectures is the often required nanomanipulation of
the objects. A restricted number of studies show the opportuni-
ties and limitations of transferring the objects from solution to
surfaces in a controlled way.4
the supramolecular organization of the building blocks. Although
the control of the chemical composition is thoroughly investi-
gated, ways to control the supramolecular organization are
deficient. The supramolecular organization is mainly investi-
gated in solution, while the organization in the solid state as
relevant to devices is almost unknown. Columnar liquid
crystalline materials as bulk materials have a high degree of
organization in the solid state, and high electron and hole
mobility have already been reported.5 Very recently, Percec et
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10.1021/ja0383118 CCC: $25.00 © 2003 American Chemical Society
J. AM. CHEM. SOC. 2003, 125, 15941-15949
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