Light-Controlled Aggregation and Gelation of Viologen-Based Coordination Polymers
journal contributionposted on 2021-10-22, 19:40 authored by Shagor Chowdhury, Quentin Reynard-Feytis, Clément Roizard, Denis Frath, Floris Chevallier, Christophe Bucher, Thomas Gibaud
Ditopic bis-(triazole/pyridine)viologens are bidentate ligands that self-assemble into coordination polymers. In such photo-responsive materials, light irradiation initiates photo-induced electron transfer to generate π-radicals that can self-associate to form π-dimers. This leads to a cascade of events: processes at the supramolecular scale associated with mechanical and structural transition at the macroscopic scale. By tuning the irradiation power and duration, we evidence the formation of aggregates and gels. Using microscopy, we show that the aggregates are dense, polydisperse, micron-sized, spindle-shaped particles which grow in time. Using microscopy and time-resolved micro-rheology, we follow the gelation kinetics which leads to a gel characterized by a correlation length of a few microns and a weak elastic modulus. The analysis of the aggregates and the gel states vouch for an arrested phase separation process, a new scenario to supramolecular systems.
weak elastic moduluspyridine ) viologensinduced electron transfergel states vouchsupramolecular scale associatedsupramolecular systemsmacroscopic scalegel characterizedusing microscopystructural transitionshaped particlesresponsive materialsresolved micronew scenarioirradiation powergenerate πform πcorrelation lengthcoordination polymerscontrolled aggregationbidentate ligands