Morphological Transitions of a Photoswitchable Aramid Amphiphile Nanostructure

• Main Authors: Kim, Dae-Yoon (Author), Christoff-Tempesta, Ty (Author), Lamour, Guillaume (Author), Zuo, Xiaobing (Author), Ryu, Ki-Hyun (Author), Ortony, Julia H (Author)
• Format: Article
• Language: English
• Published: American Chemical Society (ACS), 2022-05-16T18:48:51Z.
• Subjects: Article
• Online Access: Get fulltext

 Self-assembly of small amphiphilic molecules in water can lead to nanostructures of varying geometries with pristine internal molecular organization. Here we introduce a photoswitchable aramid amphiphile (AA), designed to exhibit extensive hydrogen bonding and robust mechanical properties upon self-assembly, while containing a vinylnitrile group for photoinduced cis-trans isomerization. We demonstrate spontaneous self-assembly of the vinylnitrile-containing AA in water to form nanoribbons. Upon UV irradiation, trans-to-cis isomerizations occur concomitantly with a morphological transition from nanoribbons to nanotubes. The nanotube structure persists in water for over six months, stabilized by strong and collective intermolecular interactions. We demonstrate that the nanoribbon-to-nanotube transition is reversible upon heating and that switching between states can be achieved repeatedly. Finally, we use electron microscopy to capture the transition and propose mechanisms for nanoribbon-to-nanotube rearrangement and vice versa. The stability and switchability of photoresponsive AA nanostructures make them viable for a range of future applications.