Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
2 Ionomers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
3 Stimuli-Responsive Metallopolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
4 Self-Healing Metallopolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
4.1 Biological Archetypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
4.2 Synthetic Self-Healing Metallopolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
4.3 Self-Healing on the Molecular Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
5 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
1 Introduction
The ground-breaking work of Lehn, Pedersen, and Cram has been honored with the
Nobel Prize in chemistry “for their development and use of molecules with
structure-specific interactions of high selectivity”, namely, for their investigations
in the field of crown ethers and host–guest interactions [1]. It was the beginning of
supramolecular chemistry as a new important research field in chemistry. Lehn
defined supramolecular chemistry as the chemistry “beyond the molecule” [2].
Structures of higher complexity are constructed and hold together by a wide range
of interactions, like hydrogen-bonding [3], hydrophobic interactions [4], π–π
stacking interactions [5], and metal–ligand interactions [6–8]. Thereby, Nature
acts as a role model by providing many inspiring examples of supramolecular
structures like the DNA structure (double helix), metallo-proteins, etc. [9]. This
field of research on noncovalent systems expands the world of covalent high
molar mass materials (i.e., synthetic macromolecules or polymers) discovered by
Staudinger, who was honored with the Noble Prize in 1953.
In recent years, an area of special interest has been identified that combines
both worlds, i.e., covalent and noncovalent macromolecules, in particular the field
of metallo(supramolecular) polymers. These materials combine many polymeric
with metal complexes and metallic properties, enabling the design of new materials
with outstanding properties, e.g., with self-X properties such as self-repair, selforganization, self-assembly, and self-healing. For instance, metallo-polymers have
also been utilized for the fabrication of stimuli-responsive structures, resulting in
reversible polymeric materials [10]. Due to this fact, metallopolymers have also
been discussed in the context of self-healing materials. Their structural elements
can feature reversible interactions similar to those known from hydrogen bonding
polymers [11–14] or reversible covalently linked polymers [9, 15–19].
The above-mentioned properties, i.e., reversibility and stimuli-responsiveness,
are directly linked to the metal–ligand binding strength. By changing the ligand(s)
and the corresponding metal ion, respectively, the intrinsic properties of the final
material can be tuned.
240
B. Sandmann et al.
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
2 Ionomers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
3 Stimuli-Responsive Metallopolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
4 Self-Healing Metallopolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
4.1 Biological Archetypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
4.2 Synthetic Self-Healing Metallopolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
4.3 Self-Healing on the Molecular Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
5 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
1 Introduction
The ground-breaking work of Lehn, Pedersen, and Cram has been honored with the
Nobel Prize in chemistry “for their development and use of molecules with
structure-specific interactions of high selectivity”, namely, for their investigations
in the field of crown ethers and host–guest interactions [1]. It was the beginning of
supramolecular chemistry as a new important research field in chemistry. Lehn
defined supramolecular chemistry as the chemistry “beyond the molecule” [2].
Structures of higher complexity are constructed and hold together by a wide range
of interactions, like hydrogen-bonding [3], hydrophobic interactions [4], π–π
stacking interactions [5], and metal–ligand interactions [6–8]. Thereby, Nature
acts as a role model by providing many inspiring examples of supramolecular
structures like the DNA structure (double helix), metallo-proteins, etc. [9]. This
field of research on noncovalent systems expands the world of covalent high
molar mass materials (i.e., synthetic macromolecules or polymers) discovered by
Staudinger, who was honored with the Noble Prize in 1953.
In recent years, an area of special interest has been identified that combines
both worlds, i.e., covalent and noncovalent macromolecules, in particular the field
of metallo(supramolecular) polymers. These materials combine many polymeric
with metal complexes and metallic properties, enabling the design of new materials
with outstanding properties, e.g., with self-X properties such as self-repair, selforganization, self-assembly, and self-healing. For instance, metallo-polymers have
also been utilized for the fabrication of stimuli-responsive structures, resulting in
reversible polymeric materials [10]. Due to this fact, metallopolymers have also
been discussed in the context of self-healing materials. Their structural elements
can feature reversible interactions similar to those known from hydrogen bonding
polymers [11–14] or reversible covalently linked polymers [9, 15–19].
The above-mentioned properties, i.e., reversibility and stimuli-responsiveness,
are directly linked to the metal–ligand binding strength. By changing the ligand(s)
and the corresponding metal ion, respectively, the intrinsic properties of the final
material can be tuned.
240
B. Sandmann et al.