interact to form hydrogels. Naphthalene diimides decorated with dipeptides have also
been shown to assemble into helical molecular fibers [29]. Faul et al. employed a
combination of hydrophobic and electrostatic interactions to assemble supramolecular
polymers from two oppositely charged dyes: a perylenediimide and a copper phthalocyanine derivative [30]. Photoactive donor (pthalocyanine) and acceptor (perylene
diimide) molecules were arranged in a “double cable” motif, addressing the concept of
molecular heterojunction systems relevant to solar energy conversion.
The complexity of aromatic self-assembly in aqueous media is exemplified by
the formation of tubular structures from relatively simple amphiphiles. The 1D
nanotubes are hierarchically ordered supramolecular polymeric structures in which
the interaction of aromatic moieties brings about an assembling motif that, in
synergy with additional interactions, results in tubular morphology [24].
For example, the nanotubes assembled from benzocoronene derivatives feature
interactions between aromatic moieties and alkyl side groups that produce separate
domains and result in long, highly ordered nanotubes [31]. Such aromatic/alkyl
interplay represents a simple yet powerful tool for controlling the self-assembly
aptitudes of aromatic amphiphiles (see Sect. 3.5). Partially oxidized benzocoronene
nanotubes exhibit electrical conduction, which is due to long-range intermolecular
electronic communication through graphite-like molecular arrays. The latter system
illustrates the power of aromatic self-assembly in water, enabling robust functional
materials constructed from small molecules.
Self-assembly of aromatic amphiphiles in aqueous media presents both opportunities and challenges: robust ordered systems with interesting functions can be easily
assembled, but the rational synthetic approaches needed to achieve such arrays remain
to be developed. In addition, an intriguing question arises: does the robust yet adaptive
character of the aromatic assemblies make them viable candidates to challenge the
performance and stability of conventional covalent materials? In the following sections
we will describe our work on encoding structures and functions in the regime of strong
hydrophobic interactions (Sect. 3), and address the challenge of creating functional
noncovalent materials for real-life applications (Sect. 4).
3 Structure Encoding
3.1 Code: Electrons/O 2 . Reversible Structure/Function
Switching via Redox Chemistry
We chose perylene diimide (PDI) as a basic aromatic unit in our systems.
PDI-based amphiphiles benefit from high stability, diverse synthetic strategies,
and advantageous photonic and electronic properties [32].
When we began working with PDI-based amphiphiles we decided to target the
simplest supramolecular structure – a 1D stacked polymeric chain that will be
robust yet adaptive (capable of reversible depolymerization). In this respect, PDI
systems have many advantages, including unique redox behavior in water: they can
Aqueous Supramolecular Polymers Based on Aromatic Amphiphiles: Rational. . .
367
been shown to assemble into helical molecular fibers [29]. Faul et al. employed a
combination of hydrophobic and electrostatic interactions to assemble supramolecular
polymers from two oppositely charged dyes: a perylenediimide and a copper phthalocyanine derivative [30]. Photoactive donor (pthalocyanine) and acceptor (perylene
diimide) molecules were arranged in a “double cable” motif, addressing the concept of
molecular heterojunction systems relevant to solar energy conversion.
The complexity of aromatic self-assembly in aqueous media is exemplified by
the formation of tubular structures from relatively simple amphiphiles. The 1D
nanotubes are hierarchically ordered supramolecular polymeric structures in which
the interaction of aromatic moieties brings about an assembling motif that, in
synergy with additional interactions, results in tubular morphology [24].
For example, the nanotubes assembled from benzocoronene derivatives feature
interactions between aromatic moieties and alkyl side groups that produce separate
domains and result in long, highly ordered nanotubes [31]. Such aromatic/alkyl
interplay represents a simple yet powerful tool for controlling the self-assembly
aptitudes of aromatic amphiphiles (see Sect. 3.5). Partially oxidized benzocoronene
nanotubes exhibit electrical conduction, which is due to long-range intermolecular
electronic communication through graphite-like molecular arrays. The latter system
illustrates the power of aromatic self-assembly in water, enabling robust functional
materials constructed from small molecules.
Self-assembly of aromatic amphiphiles in aqueous media presents both opportunities and challenges: robust ordered systems with interesting functions can be easily
assembled, but the rational synthetic approaches needed to achieve such arrays remain
to be developed. In addition, an intriguing question arises: does the robust yet adaptive
character of the aromatic assemblies make them viable candidates to challenge the
performance and stability of conventional covalent materials? In the following sections
we will describe our work on encoding structures and functions in the regime of strong
hydrophobic interactions (Sect. 3), and address the challenge of creating functional
noncovalent materials for real-life applications (Sect. 4).
3 Structure Encoding
3.1 Code: Electrons/O 2 . Reversible Structure/Function
Switching via Redox Chemistry
We chose perylene diimide (PDI) as a basic aromatic unit in our systems.
PDI-based amphiphiles benefit from high stability, diverse synthetic strategies,
and advantageous photonic and electronic properties [32].
When we began working with PDI-based amphiphiles we decided to target the
simplest supramolecular structure – a 1D stacked polymeric chain that will be
robust yet adaptive (capable of reversible depolymerization). In this respect, PDI
systems have many advantages, including unique redox behavior in water: they can
Aqueous Supramolecular Polymers Based on Aromatic Amphiphiles: Rational. . .
367