Photoreversible Supramolecular Polymerisation and Hierarchical Organization of Hydrogen‐Bonded Supramolecular Co‐polymers Composed of Diarylethenes and Oligothiophenes

Abstract

Diarylethene 1 equipped with two monotopic melamine hydrogen-bonding sites and oligothiophene-functionalized ditopic cyanurate (OTCA) were mixed in a nonpolar solvent to form AA-BB-type supramolecular co-polymers (SCPs) bearing photoswitchable moieties in their main chains and extended π systems as side chains. UV/Vis, fluorescence, dynamic light scattering (DLS), TEM, and AFM studies revealed that the two functional co-monomers formed flexible quasi-one-dimensional SCPs in solution that hierarchically self-organized into helical nanofibers through H-aggregation of the oligothiophene side chains. Upon irradiating the SCPs with UV light, a transition occurred from the H-aggregated state to non-aggregated monomeric oligothiophene side chains, as shown by spectroscopic studies, which indicates the formation of small oligomeric species held together only by hydrogen-bonding interactions. TEM and AFM visualized unfolded fibrils corresponding to elongated single SCP chains formed upon removal of solvent. The helical nanofibers were regenerated upon irradiating the UV-irradiated solution with visible light. These results demonstrated that the supramolecular polymerisation followed by hierarchical organization can be effectively controlled by proper supramolecular designs using diarylethenes and π-conjugated oligomers.

Recent advance of photochromic diarylethenes-containing supramolecular systems

“…The construction of stimuli-responsive supramolecular self-assembly has recently attracted significant interest because these assembles are promising candidates for smart materials that could find applications in chemistry, biology and material science [20][21][22]. By virtue of the significant difference of absorption spectra in open and closed forms, the morphology and chemical/physical properties of diarylethenes-based supramolecular assemblies, which are thermally irreversible, can be regulated by photoirradiation [23][24][25][26].…”

Supramolecularly Engineered Functional π-Assemblies Based on Complementary Hydrogen-Bonding Interactions

“…DAE 5 was studied for complexation with oligothiophene-functionalized cyanurate 9 (Figure 6a), 29 which has been previously shown to coassemble with a bismelamine receptor to form helical nanoaggregates (Figure 6c). Upon UVirradiation of the gels, ring-closure reaction of DAE moieties took place, which induced a gel-to-sol transition as a result of the transition of helical fibers into thin fibrils.…”

Photoswitchable Exciton Coupling in Merocyanine–Diarylethene Multi‐Chromophore Hydrogen‐Bonded Complexes

“…Because the absorption band of 2 o could be attributed to the p-p* transition of the phenylenethienylene moieties, its induced CD signal strongly suggests that this molecule adopts the parallel conformation [13] upon complexation with 1. The complexation-induced CD signal of 2 o was not observed when nonchromophoric N-dodecylcyanurate [10] was used as a guest, indicating that the J-type aggregation of 1 is responsible for the formation of the specific assemblies.…”

“…[9] From the spectroscopic and the NMR studies, it was suggested that the formation of discrete oligomers (1 + BM3) and folded supramolecular polymers (1 + BM12) are responsible for such contrasting exciton interactions. In the present study melamine-equipped diarylethene 2 [10] was used as a photoresponsive receptor for 1. Chiral substituents [11] were introduced to melamine moieties to induce chiral exciton coupling, which is conveniently studied by circular dichroism (CD) spectroscopy.…”