16.1 Introduction
Owing to their potential applications in the fields of optics, biology, and medicine,
supramolecular materials are drawing more and more attention from researchers.
Supramolecular polymers are constructed from monomer components, small supramolecular systems, or polymers that are repeatedly linked by such reversible noncovalent interactions as hydrogen bonds, π-π stacking, hydrophobic effects,
host–guest interaction, and electrostatic interactions [1]. Since the noncovalent
interactions are reversible, supramolecular polymers tend to make differences to
external factors, such as pH changes, chemical and electrochemical redox, light
stimulation, temperature/concentration changes, enzyme stimuli, etc. and accompanied by assembly conformation or property changes.
The host–guest interaction is the driving force of the host–guest complex, which
involves the synergy of a variety of noncovalent bonds, such as hydrophobic
interactions, hydrogen bonds, ionic bonds, van der Waals forces, and electrostatic
interactions. Since the discovery of cryptands and crown ethers by Lehn, Cram,
and Pedersen, the host–guest system has greatly contributed to the development
of supramolecular chemistry. As the name suggests, the host–guest system consists
mainly of two components: the host and the guest, which form the supramolecular
inclusion. The host molecule usually contains a cavity that specifically recognizes
the guest molecule. The host–guest function has characteristic selectivity, because
the subject has various restrictions on the object, such as size, shape, charge, and
polarity. In the development of supramolecular chemistry, the control and regulation
of molecular recognition based on host–guest interaction in supramolecular polymers has attracted a lot of attention [2]. The mechanism of polymerization and the
nature of the polymer are determined by the strength and nature of the host–guest
units.
The host molecules involved in the preparation of supramolecular polymers based
on host–guest systems are typically crown ethers, cyclodextrins, cucurbiturils,
calixarenes, and column aromatics. And the guest molecules are generally organic
compounds that can enter the bulky cavity. In the following, we will outline the
development of photoresponsive supramolecular polymers in this field according to
the classification of the host molecules.
Organic materials have many advantages such as good regulation, rich color,
smart molecular design, low cost, and toxicity compared with inorganic materials.
The combination of supramolecular chemistry to construct highly efficient luminescent materials not only simplifies the preparation process but also imparts good
stimuli responsiveness and reversibility to these materials through noncovalent
attachment. The noncovalently guided assembly–disassembly process can affect
the aggregation and energy transfer between the fluorophores [3], thus regulate
the luminescence behavior of the materials. Therefore, luminescent systems
constructed concerning supramolecular systems are generally capable of responding
to external stimuli such as pH, temperature, solvent polarity, light radiation, redox,
etc. accompanied by reversible conformation and structural transformation. In recent
years, materials with tunable luminescence properties have been demonstrated their
452
F. Gu and X. Ma
Owing to their potential applications in the fields of optics, biology, and medicine,
supramolecular materials are drawing more and more attention from researchers.
Supramolecular polymers are constructed from monomer components, small supramolecular systems, or polymers that are repeatedly linked by such reversible noncovalent interactions as hydrogen bonds, π-π stacking, hydrophobic effects,
host–guest interaction, and electrostatic interactions [1]. Since the noncovalent
interactions are reversible, supramolecular polymers tend to make differences to
external factors, such as pH changes, chemical and electrochemical redox, light
stimulation, temperature/concentration changes, enzyme stimuli, etc. and accompanied by assembly conformation or property changes.
The host–guest interaction is the driving force of the host–guest complex, which
involves the synergy of a variety of noncovalent bonds, such as hydrophobic
interactions, hydrogen bonds, ionic bonds, van der Waals forces, and electrostatic
interactions. Since the discovery of cryptands and crown ethers by Lehn, Cram,
and Pedersen, the host–guest system has greatly contributed to the development
of supramolecular chemistry. As the name suggests, the host–guest system consists
mainly of two components: the host and the guest, which form the supramolecular
inclusion. The host molecule usually contains a cavity that specifically recognizes
the guest molecule. The host–guest function has characteristic selectivity, because
the subject has various restrictions on the object, such as size, shape, charge, and
polarity. In the development of supramolecular chemistry, the control and regulation
of molecular recognition based on host–guest interaction in supramolecular polymers has attracted a lot of attention [2]. The mechanism of polymerization and the
nature of the polymer are determined by the strength and nature of the host–guest
units.
The host molecules involved in the preparation of supramolecular polymers based
on host–guest systems are typically crown ethers, cyclodextrins, cucurbiturils,
calixarenes, and column aromatics. And the guest molecules are generally organic
compounds that can enter the bulky cavity. In the following, we will outline the
development of photoresponsive supramolecular polymers in this field according to
the classification of the host molecules.
Organic materials have many advantages such as good regulation, rich color,
smart molecular design, low cost, and toxicity compared with inorganic materials.
The combination of supramolecular chemistry to construct highly efficient luminescent materials not only simplifies the preparation process but also imparts good
stimuli responsiveness and reversibility to these materials through noncovalent
attachment. The noncovalently guided assembly–disassembly process can affect
the aggregation and energy transfer between the fluorophores [3], thus regulate
the luminescence behavior of the materials. Therefore, luminescent systems
constructed concerning supramolecular systems are generally capable of responding
to external stimuli such as pH, temperature, solvent polarity, light radiation, redox,
etc. accompanied by reversible conformation and structural transformation. In recent
years, materials with tunable luminescence properties have been demonstrated their
452
F. Gu and X. Ma