Wholly-rigid rod–rod amphiphiles: synthesis,crystal structures,and self-assembling behavior in water

A series of fully rigid rod–rod type amphiphilic molecules have been constructed by using 4,4′-bipyridin-1-ium or 4,4′-bipyridin-1,1′-diium (viologen) as a hydrophilic segment and phenyl, biphenyl or para-tert-phenyl as a hydrophobic unit. The crystal structures of four of the molecules have been elucidated. TEM, SEM, AFM, and DLS experiments revealed that these stiff amphiphiles could self-assemble into diverse architectures, including spherical micelles, ultra-long straight nanofibers (>1 mm), and nanotubes in water, which depend on the hydrophilic/hydrophobic fraction ratios of the molecules.