Furthermore, these issues could influence the charge carrier mobilities that are
required for applications as photovoltaic solar cells and field-effect transistors [209].
This is indeed the case for perylene bisdiimides (PBI) functionalized with
dendritic goups. These dendronized PBIs self-assemble into a complex helical
column generated from tetramers containing a pair of molecules arranged sideby-side and another pair in the next stratum of the column, turned upside-down and
rotated around the column axis at an intratetramer angle that is different from that of
the intertetramer angle (Fig. 53). In most cases, the intratetramer stacking distance
in this column is 4.1 A ˚ , while the intertetramer distance is 3.5 A ˚ . The architecture
of this complex helical column, the structure of its 3D periodic array, and its
kinetically controlled self-organization with such a long intrateramer distance are
not ideal for the design of supramolecular structures with high charge carrier
mobility. In fact, the mobility of electrons is only moderate. However, in some
cases heating above 100
C into the LC phase optimizes the packing, resulting in
shorter intertetramer distances and much higher charge mobilities [210], This is
accompanied by substantial narrowing of the
1
H NMR lines. Computer simulation
showed that this narrowing of the NMR spectra indicates a complex reorganization
mechanism, where the PBI molecules leave the supramolecular column, flip over,
and reenter a column at a later time (Fig. 53) [210].
4.7 Conclusions
The examples briefly reviewed here demonstrate that the interplay of synthesis,
multi-technique characterization and computer simulation is crucial for the development of functional materials based on supramolecular organization of carefully
designed building blocks. Local conformation, intrinsic mobility, incompatibility,
and well-established noncovalent interactions such as hydrogen bonds or π–π
interactions can govern self-assembly in highly specific ways. Moreover, complex
molecular dynamics is relevant for generating stable structures with desired
properties such as high charge carrier mobility. In contrast, ill-defined sample
preparation can lead to partially disordered structures with inferior properties.
Magnetic resonance, both NMR and EPR, can provide unique detailed information
about all these aspects over large ranges in space and time. Therefore, these
techniques play an important role in the generation of functional organic materials.
5 Block Copolymers and Confinement
This section deals with the influence of amphiphilicity on the formation of block
copolymer structures. These block copolymers are either confined in the spherical
shape of a nanodroplet or on a surface. Whereas in the first case, the fundamental
aspects of mesoscospic structure formation are the focus of attention, we concentrate in the second case on a specific function, i.e., switchable wettability due to the
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K. Binder et al.
required for applications as photovoltaic solar cells and field-effect transistors [209].
This is indeed the case for perylene bisdiimides (PBI) functionalized with
dendritic goups. These dendronized PBIs self-assemble into a complex helical
column generated from tetramers containing a pair of molecules arranged sideby-side and another pair in the next stratum of the column, turned upside-down and
rotated around the column axis at an intratetramer angle that is different from that of
the intertetramer angle (Fig. 53). In most cases, the intratetramer stacking distance
in this column is 4.1 A ˚ , while the intertetramer distance is 3.5 A ˚ . The architecture
of this complex helical column, the structure of its 3D periodic array, and its
kinetically controlled self-organization with such a long intrateramer distance are
not ideal for the design of supramolecular structures with high charge carrier
mobility. In fact, the mobility of electrons is only moderate. However, in some
cases heating above 100
C into the LC phase optimizes the packing, resulting in
shorter intertetramer distances and much higher charge mobilities [210], This is
accompanied by substantial narrowing of the
1
H NMR lines. Computer simulation
showed that this narrowing of the NMR spectra indicates a complex reorganization
mechanism, where the PBI molecules leave the supramolecular column, flip over,
and reenter a column at a later time (Fig. 53) [210].
4.7 Conclusions
The examples briefly reviewed here demonstrate that the interplay of synthesis,
multi-technique characterization and computer simulation is crucial for the development of functional materials based on supramolecular organization of carefully
designed building blocks. Local conformation, intrinsic mobility, incompatibility,
and well-established noncovalent interactions such as hydrogen bonds or π–π
interactions can govern self-assembly in highly specific ways. Moreover, complex
molecular dynamics is relevant for generating stable structures with desired
properties such as high charge carrier mobility. In contrast, ill-defined sample
preparation can lead to partially disordered structures with inferior properties.
Magnetic resonance, both NMR and EPR, can provide unique detailed information
about all these aspects over large ranges in space and time. Therefore, these
techniques play an important role in the generation of functional organic materials.
5 Block Copolymers and Confinement
This section deals with the influence of amphiphilicity on the formation of block
copolymer structures. These block copolymers are either confined in the spherical
shape of a nanodroplet or on a surface. Whereas in the first case, the fundamental
aspects of mesoscospic structure formation are the focus of attention, we concentrate in the second case on a specific function, i.e., switchable wettability due to the
176
K. Binder et al.