solution) on the membrane, and an activity assay solution containing a substrate (onitrophenyl-β-galactoside, ONPG) was run through it, resulting in enzyme-catalyzed
hydrolysis of ONPG, as manifested by the yellow color of the reaction product
(Fig. 16c). The biocatalytic conversion is very stable; it was performed for 6 h
under a continuous flow of substrate through the membrane, exhibiting a constant
reaction yield of 90% [67]. Overall, our water-based noncovalent membranes are
robust, recyclable, and biocompatible, suggesting new avenues for manipulating
biological systems.
Addressing the viability and versatility of water-based noncovalent polymeric
materials, we have shown that hydrophobic interactions are adequate for creating
noncovalent membranes for size-selective separation of nanoparticles and proteins.
These membranes exhibit separation properties similar to their covalent counterparts. Unlike conventional membranes, our systems are fully recyclable and more
versatile, shaping a paradigm of water-based materials as a viable alternative to
covalent systems.
5 Summary
Supramolecular polymers constructed from aromatic amphiphiles in aqueous media
can be based on several design concepts. One design is derived from an analogy
with hydrogen bonding and relies on pairwise directional interactions. Another
design utilizes the intrinsic anisotropy of hydrophobic interactions stemming from
aromatic and aliphatic moieties. The outcome of self-assembly in this case can be
controlled via tuning of the size and nature of the aromatic, aliphatic, and hydrophilic groups, whose hierarchical assembly modes enable noncovalent synthesis of
photofunctional fibers or crystalline arrays. Coordination chemistry has proven to
be a convenient tool for promoting diversity-oriented noncovalent synthesis.
Furthermore, strong hydrophobic interactions can lead to a breakdown of thermodynamic control; thus, kinetic trapping can be used to regulate self-assembly,
enabling diversity and complex supramolecular transformations, where pathwaydependence serves as a powerful synthetic tool. We believe that an important future
research direction is mechanistic studies, so that supramolecular transformations
will be rationally designed on the basis of retrosynthetic approaches. This requires
creating an intellectual framework for noncovalent synthesis, akin to the mechanistically driven methodologies used for covalent synthesis.
Water-based noncovalent polymeric materials such as adaptive membranes or
robust self-healing plastic-like hydrogels may generate a paradigm shift in material
science, thus introducing the concept of recyclable/self-healing materials that
perform as well as the covalent materials, while being more adaptive, versatile,
and prone to advantageous fabrication and processing. Similarly to biological
systems, these materials largely consist of water, which also make them costefficient and environmentally friendly.
Aqueous Supramolecular Polymers Based on Aromatic Amphiphiles: Rational. . .
385
hydrolysis of ONPG, as manifested by the yellow color of the reaction product
(Fig. 16c). The biocatalytic conversion is very stable; it was performed for 6 h
under a continuous flow of substrate through the membrane, exhibiting a constant
reaction yield of 90% [67]. Overall, our water-based noncovalent membranes are
robust, recyclable, and biocompatible, suggesting new avenues for manipulating
biological systems.
Addressing the viability and versatility of water-based noncovalent polymeric
materials, we have shown that hydrophobic interactions are adequate for creating
noncovalent membranes for size-selective separation of nanoparticles and proteins.
These membranes exhibit separation properties similar to their covalent counterparts. Unlike conventional membranes, our systems are fully recyclable and more
versatile, shaping a paradigm of water-based materials as a viable alternative to
covalent systems.
5 Summary
Supramolecular polymers constructed from aromatic amphiphiles in aqueous media
can be based on several design concepts. One design is derived from an analogy
with hydrogen bonding and relies on pairwise directional interactions. Another
design utilizes the intrinsic anisotropy of hydrophobic interactions stemming from
aromatic and aliphatic moieties. The outcome of self-assembly in this case can be
controlled via tuning of the size and nature of the aromatic, aliphatic, and hydrophilic groups, whose hierarchical assembly modes enable noncovalent synthesis of
photofunctional fibers or crystalline arrays. Coordination chemistry has proven to
be a convenient tool for promoting diversity-oriented noncovalent synthesis.
Furthermore, strong hydrophobic interactions can lead to a breakdown of thermodynamic control; thus, kinetic trapping can be used to regulate self-assembly,
enabling diversity and complex supramolecular transformations, where pathwaydependence serves as a powerful synthetic tool. We believe that an important future
research direction is mechanistic studies, so that supramolecular transformations
will be rationally designed on the basis of retrosynthetic approaches. This requires
creating an intellectual framework for noncovalent synthesis, akin to the mechanistically driven methodologies used for covalent synthesis.
Water-based noncovalent polymeric materials such as adaptive membranes or
robust self-healing plastic-like hydrogels may generate a paradigm shift in material
science, thus introducing the concept of recyclable/self-healing materials that
perform as well as the covalent materials, while being more adaptive, versatile,
and prone to advantageous fabrication and processing. Similarly to biological
systems, these materials largely consist of water, which also make them costefficient and environmentally friendly.
Aqueous Supramolecular Polymers Based on Aromatic Amphiphiles: Rational. . .
385