Photoresponsive chiral nanotubes of achiral amphiphilic azobenzene

Abstract

Supramolecular chirality has generally been fabricated by an aggregation process of chiral building blocks. Herein, we report the fabrication of the soft chiral nanotubes by chiral self-assembly, exclusively from a novel designed achiral carboxylic-substituted bolaamphiphilic azobenzene. Based on the studies with UV-vis absorption, circular dichroism (CD), transmission electron microscopy (TEM), and X-ray diffraction (XRD) spectra, a plausible mechanism by which a chirally helical shape emerges from the nonsymmetric packing of an achiral molecule has been proposed. Our results demonstrate a valid approach for correlating the molecular structure to the macroscopic properties, in which, by ingenious molecular design, supramolecular chirality can be achieved from achiral molecular building blocks. It was further revealed that the morphology and chirality of the self-assembled nanostructures change in response to external stimuli such as light and heat. This should open an avenue for a good understanding of the ways in which structural variation affects self-assembled structures at the molecular level. We should also find potential applications as smart carriers for the controlled release and site-specific targeting of the loading, modulated by environmental stimuli.

Polymorphic transformation towards formation of nanotubes by self-assembly of an achiral molecule

“…[50][51][52] If such kinds of molecules can also undergo a similar morphic transition to the molecules with a chiral center, the result would be very interesting and serve as an expansion to the theory proposed by Selinger et al [50][51][52] If such kinds of molecules can also undergo a similar morphic transition to the molecules with a chiral center, the result would be very interesting and serve as an expansion to the theory proposed by Selinger et al…”

Colloidal chirality in wormlike micellar systems exclusively originated from achiral species: Role of secondary assembly and stimulus responsivity

“…As for the overall macroscopic chirality it is still an interesting topic to exploit. Our previous work in soft matter shows the chirality by the achiral molecule [39]. However, the supramolecular chirality herein in this work concerns a new type of colloidal aggregates, wormlike micelles (one kind of typical cylindrical soft aggregate).…”

Switchable Solubility of Azobenzene‐Based Bolaamphiphiles

“…In the case of azobenzene, absorption of photons induces a reversible change in N=N bond geometry . The resulting changes in cis/trans configuration and dipole moment allow tuning the solution properties of azobenzene‐based bolaamphiphiles by irradiation with light of low intensity . This enabled the development of photo‐switchable surface agents, hydrogelators, and supramolecular aggregates with great potential for biomedical applications …”

“…With the aim of gaining remote control over the solution properties of bolaamphiphiles, many photo-responsive systems, such as azobenzene, [17][18][19][20][21][22][23][24] thymine, [25] or stilbene, have been introduced. [26,27] In the case of azobenzene, absorption of photons induces a reversible change in N=N bond geometry.…”

“…[28,29] The resulting changes in cis/trans configuration and dipole moment allow tuning the solution properties of azobenzene-based bolaamphiphiles by irradiation with light of low intensity. [17][18][19][20][21][22][23][24] This enabled the development of photoswitchable surface agents, hydrogelators, and supramolecular aggregates with great potential for biomedical applications. [17][18][19][20][21][22][23][24] Due to the diversity of available bolaamphiphiles, it remains challenging to rationalize design guidelines that allow a predictable tuning of their solution properties.…”