Dual-Responsive Ultrathin Peptoid Nanofibers Assembled from Amphiphilic Alternating Peptoids with an Integration of Azobenzene and Histamine Moieties

Ultrathin organic nanofibers (UTONFs) have favorable potential as emerging nanomaterials due to their large aspect ratio, lightweight nature, and mechanical flexibility. Achieving dual stimuli-responsive UTONFs is necessary to satisfy the on-demand requirements of smart and miniature devices but remains challenging. Herein, amphiphilic alternating peptoids (AAPs) modified with azobenzene and histamine groups were successfully synthesized using the solid-phase submonomer synthesis technique. Following subsequent solution self-assembly, photo/CO2 dual-responsive ultrathin peptoid nanofibers (UTPNFs) with a diameter of ∼1.8 nm and a length of up to several micrometers were generated based on the pendant hydrophobic conjugate stacking mechanism. The photoisomerization of azobenzene was accountable for the reversible transformation from UTPNFs to spherical micelles (∼60 nm) under recyclable light irradiation. Owing to the protonation and the resulting electrostatic repulsion interaction, both UTPNFs and spherical micelles displayed a reversible variation in shape and physicochemical properties, including the size, diameter, zeta potential, and pH. Our work offers prospective guidance on the construction of dual-responsive ultrathin organic nanofibers with controllable shape transformation and performance transition.