Another reported case of the rod-selective solvent system involves PANI-b-PEG-b-PANI triblock polymers in mixed solvents of THF/diethyl ether [106]. In a THF solution, the micelles with a middle-layer was formed by the π–π stacking of the PANI segments while the PEG segments aggregated anisotropically in two dimensions to form the up and down layers of a sandwich structure. By adding the rod-selective diethyl ether solvent, the micelles changed into the spring-like helical superstructures for short PANI block, but presented fibrous helical superstructures for longer PANI blocks. Such helical superstructures probably resulted from the twist of the belt-like structure grown from the π–π stacking of PANI.