Supramolecular Polymerization Controlled by Reversible Conformational Modulation

Shape-Assisted Self-Assembly of Hexa-Substituted Carpyridines into 1D Supramolecular Polymers

The extent of the influence that molecular curvature plays on the self-assembly of supramolecular polymers remains an open question in the field. We began addressing this fundamental question with the introduction of "carpyridines", which are saddle-shaped monomers that can associate with one another through π-π interactions and in which the rotational and translational movements are restricted. The topography displayed by the monomers led, previously, to the assembly of highly ordered 2D materials even in the absence of strong directional interactions such as hydrogen bonding. Here, we introduce a simple strategy to gain control over the dimensionality of the formed structures yielding classical unidimensional polymers. These have been characterized using well-established protocols allowing us to determine and confirm the self-assembly mechanism of both fibers and sheets. The calculated interaction energies are significantly higher than expected for flexible self-assembling units lacking classical "strong" non-covalent interactions. The versatility of this supramolecular unit to assemble into either supramolecular fibers or 2D sheets with strong association energies highlights remarkably well the potential and importance of molecular shape for the design of supramolecular materials and the applications thereof.

Chiral Supramolecular Polymers Assembled from Conformationally Flexible Amino-Acid-Substituted Biphenyldiimides

Hydrogen-bonded polymers are a class of highly dynamic supramolecular aggregates, whose self-assembly may be tuned by very mild external or internal stimuli. However, the rational design of chiral supramolecules remains challenging especially when flexible components are involved. The combination of the inherent weakness and dynamic nature of the intermolecular bonds that hold together such assemblies with unrestricted molecular motions introduces additional factors which may affect the self-assembly process. In this report, the self-assembly of four amino acid-derived chiral biphenyldiimides into open-chain 1D supramolecular polymers is presented. While the primary driving force, COOH···HOOC hydrogen bonding, is responsible for the polymer growth in all cases, the amino acid side chains play an important role in either stabilizing or destabilizing the assemblies obtained, as deduced from studies of the thermodynamics of the self-assembly process. Furthermore, substantial differences in the structural factors governing the polymerization process between dynamic liquid and static solid are found. This work demonstrates the potential of the rather unexplored class of diimide-based organic dyes in the formation of well-organized chiral supramolecular assemblies with tunable properties.

A Strategy Based on Aggregation-Induced Ratiometric Emission to Differentiate Molecular Weight of Supramolecular Polymers

Molecular weight has an important bearing on the properties of supramolecular polymers. However, the intuitive differentiation of the molecular weight of supramolecular polymers remains challenging. Given this situation, establishing a reliable relationship between fluorescence properties and molecular weight may be a promising strategy. Herein, we prepared a supramolecular monomer M1 with aggregation-induced ratiometric emission characteristics. With the increasing M1 concentration (0.100-100 mM), the average degree of polymerization (DP_DOSY ) rose from 1.00 to 293. Meanwhile, the color changed from dark blue to cyan, finally to yellow-green in the same concentration range. Hence, the intuitive relationship between DP_DOSY and fluorescence colors was constructed, allowing the visual differentiation of molecular weight. Moreover, the fluorescence color could be regulated by introducing a competitive molecule to induce the depolymerization of supramolecular polymers.

Supramolecular Emulsion Interfacial Polymerization

A new method of supramolecular emulsion interfacial polymerization is developed, which can be used to fabricate supramolecular polymeric nanospheres. We designed a water-soluble monomer containing two maleimide end groups, acting as both building block and surfactant, and an oil-soluble supramonomer bearing two thiol groups connected by quadruple hydrogen bonds. With the assist of ultrasonication, hollow nanospheres can be controllably prepared by thiol-maleimide reaction of two monomers at the emulsion interface, which exhibit good stability and dynamic property. In addition, the encapsulated guest molecules could be controllably released from the supramolecular polymeric nanospheres, owing to their stimuli-responsiveness. It is anticipated that this approach will enrich the methodology of supramolecular polymerization and can be applied to constructing supramolecular materials with controllable structures and functions.

Photoresponsive supramolecular polymers based on quadruple hydrogen-bonding and a photochromic azobenzene motif

A photoresponsive quadruple hydrogen-bonded supramolecular polymer was constructed using photochromic azobenzene and ureidopyrimidinone motifs.

A thermoresponsive supramolecular polymer gel from a heteroditopic calix[4]pyrrole

Anion recognition was utilized on heteroditopic calix[4]pyrrole host–guest systems to obtain a thermoresponsive supramolecular polymer gel.

Supramolecular Porphyrin Photosensitizers: Controllable Disguise and Photoinduced Activation of Antibacterial Behavior

A series of supramolecular photosensitizers were fabricated from porphyrin derivatives (Por) containing quaternary ammonium groups with cucurbit[7]uril (CB[7]) based on host-guest interactions. The antibacterial activity of Por in the dark could be turned off upon binding with CB[7], whereas the antibacterial activity under white-light illumination could be turned on. In addition, its antibacterial efficiency could be greatly enhanced by introducing metal ions. When Pd(II) was introduced into porphyrin, its antibacterial efficiency was enhanced from 40 to 100%. It should be noted that these small molecules showed little to no cytotoxicity toward mammalian cells even at concentrations higher than those under the antibacterial condition studied. This line of research will provide a strategy for germicides consisting of quaternary ammonium groups to fight against bacterial accumulation in the long term and holds huge potential for application in the real world.

Controllable Supramolecular Polymerization Promoted by Host-Enhanced Photodimerization

In this letter, we report a new method of controllable supramolecular polymerization, taking advantage of host-enhanced photodimerization. The low-molecular-weight supramolecular oligomers were formed by noncovalent complexation between cucurbit[8]urils (CB[8]) and the bifunctional monomers (DBN) with Brooker's merocyanine moiety (MOED) on either end. Interestingly, when irradiated with UV light, the supramolecular oligomers could transform into supramolecular polymers with high molecular weight. The molecular weight of supramolecular polymers could be controlled by varying the irradiation time. It is highly anticipated that this work can enrich the methods on the modulation of supramolecular polymerization.

Supramolecular Microgels Fabricated from Supramonomers

This letter describes a new method for fabricating supramolecular microgels from supramonomers. To this end, we designed and assembled supramonomers with one acrylate moiety on each end on the basis of noncovalent host-guest interactions, which could be utilized as a cross-linker. Then supramolecular microgels were fabricated through the copolymerization of supramonomers and N-isopropylacrylamide (NIPAm). The supramolecular microgels not only showed temperature-responsive properties as expected from conventional PNIPAm-based microgels but also exhibited stimuli-responsive and degradable properties benefiting from the dynamic nature of supramonomers. In addition, it was found that the degradation kinetics of the supramolecular microgels was related greatly to the structure of the microgels, providing a way to tune the degradation kinetics of the supramolecular microgels. Various supramolecular microgels with desired structure and function are supposed to be facilely fabricated from supramonomers. It is anticipated that the supramolecular microgels can enrich the application of microgels by easily endowing the microgels with stimuli-responsive and degradable properties.

Synthesis of a disulfide-bridged bispillar[5]arene and its application in supramolecular polymers

A disulfide-bridged bispillar[5]arene was synthesized efficiently and applied to fabricate supramolecular polymers, which were redox-responsive and could be used to prepare fluorescent water-dispersible nanospheres.

Photo-responsive supramolecular polymers synthesized by olefin metathesis polymerization from supramonomers

This communication reports the construction of photo-responsive supramolecular polymers that are synthesized by olefin metathesis polymerization from quadruple hydrogen bonded supramonomers.