Bis‐Bipyridinium Gemini Surfactant‐Based Supramolecular Helical Fibers and Solid State Thermochromism

Abstract

The processability and functional performance of stimuli-responsive supramolecular materials are key factors in determining their utility and potential for mass adoption, usage, and profitability. However, it is difficult to predict how structural changes to the molecular components of these systems will impact their operation. Here, a series of π-electron-deficient bis-bipyridinium gemini surfactants were synthesized and evaluated to elucidate the structure-property relationships that govern their ability to form helical-fiber-based donor-acceptor hydrogels, impact hydrogel strength, and influence their solid-state thermochromism. When combined with the π-electron-rich donor melatonin, the helical-fiber- and hydrogel-forming ability of the gemini surfactants was largely influenced by the dimensions of the rigid bridging group that connects the two bis-bipyridinium units. Dynamic viscoelastic rheology and linear sweep voltammetric analysis revealed a positive correlation between the length of the gemini-surfactant bridging group and both the hydrogel strength and the magnitude of the charge-transfer interaction between the donor-acceptor pair. Solid-state thermochromic transition temperatures of processed aerogels, xerogel films, and inkjet-printed patterns were positively correlated with the strength of the charge transfer interaction between the donor-acceptor pair and, thus, also with the length of the gemini surfactant bridging group. The results provide impactful insights that will enable the development of new donor-acceptor-based thermochromes with versatile processability and tunable functionality.

Light-controlled aggregation and gelation of viologen-based coordination polymers

“…Such a scenario is new to supramolecular systems but has already been observed in colloidal dispersions [67], polymers [68] and proteins solutions [69]. It opens up new perspectives in the field of viologen-based responsive supramolecular gels [7][8][9][10][11]. This work provides a physical analysis of a highly complex chemical system.…”

“…Those materials may in particular self-assemble into a wide variety of structures ranging from aggregates, capsules, gels or textured thin films [1]. The gel state [2][3][4][5][6][7][8][9][10][11] is an interesting class of soft materials with broad potential applications ranging from structure directing agents for the synthesis of nanoporous materials, surface patterning, ink, 3D printing to pollutant removal and biomedical applications [12][13][14][15][16].…”

“…Here, we take advantage of the photo-sensitivity of viologen-based supramolecular polymers [7][8][9][10][11][19][20][21][22][23] to direct the self-assembly toward aggregates or gels.…”

Light-Controlled Aggregation and Gelation of Viologen-Based Coordination Polymers

“…Those materials may in particular self-assemble into a wide variety of structures ranging from aggregates, capsules, gels, or textured thin films . The gel state − is an interesting class of soft materials with broad potential applications ranging from structure directing agents for the synthesis of nanoporous materials, surface patterning, ink, 3D printing to pollutant removal, and biomedical applications. − …”

Photoredox Processes in the Aggregation and Gelation of Electron-Responsive Supramolecular Polymers Based on Viologen

“…9,[12][13][14][15][16] The incorporation of redox/photo-active units based on N,N′disubstituted 4,4′-bispyridinium salts, commonly known as viologens, in the structure of gels has been shown to confer interesting electron-accepting and photo/electrochromic properties to the responsive molecular materials. [17][18][19][20][21][22][23] These responsive units have already been used as key elements for the development of electrochromic devices, molecular machines and organic batteries. 24 Recently, viologens have also been used as redox-responsive components in molecular junctions showing great promises for uses as conductive material in molecular electronics.…”