Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
2 Aromatic Amphiphiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
3 Structure Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
3.1 Code: Electrons/O 2 . Reversible Structure/Function Switching via Redox
Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
3.2 Code: Metal Coordination. Diversity via Coordination Chemistry . . . . . . . . . . . . . . . . . 369
3.3 Code: The Self-Assembly Pathway. Complexity via Kinetic Control . . . . . . . . . . . . . . 371
3.4 Code: Directional Pairwise Hydrophobic Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
3.5 Code: Anisotropic Hierarchical Hydrophobic Interactions. 2D Crystalline Arrays. 375
4 Water-Based Noncovalent Polymeric Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
4.1 Adaptive Hydrogel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
4.2 Recyclable Noncovalent Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386
1 Introduction
Research on supramolecular polymers represents a central theme in supramolecular
science [1]. From a fundamental standpoint, one-dimensional supramolecular fiber is
the simplest supramolecular motif and serves as an analog of covalent polymeric chains.
Noncovalent supramolecular polymers have two main advantages in comparison with
their covalent counterparts: they are easy to make using self-assembly and they are
adaptive, i.e., capable of structural changes and depolymerization by external stimuli
[1]. However, these attractive properties present key challenges related to robustness
and rational design: noncovalent interactions result in relatively weak bonds, whereas
multiple molecular units and interaction modes render synthesis of predesigned structures very difficult.
Noncovalent interactions in water are crucial in biological systems, providing
bonding motifs that are robust yet adaptive [2], and mediate unique molecular
recognition patterns [3]. Is it possible to utilize the unique properties of water by
employing synthetic amphiphiles in order to create supramolecular polymers with
high robustness? If so, can we rationally design such water-based noncovalent
polymers? Can we program them to perform useful functions?
A number of supramolecular systems in water display ample robustness.
For example, noncovalent interactions have been employed to create stable macroscopic sacs [4], a self-healing hydrogel having exceptional mechanical strength [5],
and multifunctional stimuli-responsive molecular printboards [6]. Hydrophobic interactions have been recently shown to induce a dramatic change in chemical properties.
Thus, pyrophoric white phosphorus (P 4 ) that ignites in air is rendered air-stable within
the hydrophobic cavities of self-assembled cage molecules in water, but is readily
oxidized when displaced from a cavity with a more strongly binding guest molecule
[7], thus demonstrating its adaptivity. Supramolecular fibers and their threedimensional (3D) networks in water, as well as supramolecular hydrogels, can be
sufficiently robust and biocompatible for biomedical applications [8].
364
B. Rybtchinski
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
2 Aromatic Amphiphiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
3 Structure Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
3.1 Code: Electrons/O 2 . Reversible Structure/Function Switching via Redox
Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
3.2 Code: Metal Coordination. Diversity via Coordination Chemistry . . . . . . . . . . . . . . . . . 369
3.3 Code: The Self-Assembly Pathway. Complexity via Kinetic Control . . . . . . . . . . . . . . 371
3.4 Code: Directional Pairwise Hydrophobic Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
3.5 Code: Anisotropic Hierarchical Hydrophobic Interactions. 2D Crystalline Arrays. 375
4 Water-Based Noncovalent Polymeric Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
4.1 Adaptive Hydrogel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
4.2 Recyclable Noncovalent Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386
1 Introduction
Research on supramolecular polymers represents a central theme in supramolecular
science [1]. From a fundamental standpoint, one-dimensional supramolecular fiber is
the simplest supramolecular motif and serves as an analog of covalent polymeric chains.
Noncovalent supramolecular polymers have two main advantages in comparison with
their covalent counterparts: they are easy to make using self-assembly and they are
adaptive, i.e., capable of structural changes and depolymerization by external stimuli
[1]. However, these attractive properties present key challenges related to robustness
and rational design: noncovalent interactions result in relatively weak bonds, whereas
multiple molecular units and interaction modes render synthesis of predesigned structures very difficult.
Noncovalent interactions in water are crucial in biological systems, providing
bonding motifs that are robust yet adaptive [2], and mediate unique molecular
recognition patterns [3]. Is it possible to utilize the unique properties of water by
employing synthetic amphiphiles in order to create supramolecular polymers with
high robustness? If so, can we rationally design such water-based noncovalent
polymers? Can we program them to perform useful functions?
A number of supramolecular systems in water display ample robustness.
For example, noncovalent interactions have been employed to create stable macroscopic sacs [4], a self-healing hydrogel having exceptional mechanical strength [5],
and multifunctional stimuli-responsive molecular printboards [6]. Hydrophobic interactions have been recently shown to induce a dramatic change in chemical properties.
Thus, pyrophoric white phosphorus (P 4 ) that ignites in air is rendered air-stable within
the hydrophobic cavities of self-assembled cage molecules in water, but is readily
oxidized when displaced from a cavity with a more strongly binding guest molecule
[7], thus demonstrating its adaptivity. Supramolecular fibers and their threedimensional (3D) networks in water, as well as supramolecular hydrogels, can be
sufficiently robust and biocompatible for biomedical applications [8].
364
B. Rybtchinski