3.2.1. Rod-selective solvent system
In the rod-selective solvent system, the aggregated shape of conjugated rods affecting the photophysical properties was well addressed by Jenekhe and Chen [56] and [57]. Diverse aggregated morphologies of PPQ-b-PS were observed at different compositions of mixed trifluoroacetic acid (TFA)/dichloromethane (DCM) solvents, including spheres, lamellae, cylinders, and vesicles. Note that TFA was a good solvent for the PPQ block and DCM was acted as a common solvent for both blocks. The spherical and cylindrical aggregates were further processed to form large hollow cavities with a PS inner shell and a PPQ outer shell. In addition, all of the different PPQ aggregates were observed with highly ordering crystalline features. Such different aggregation shapes led to distinct luminescence emission spectra and time-resolved photoluminescence decay dynamics. However, only the vesicular morphology was obtained for a triblock PPQ-b-PS-b-PPQ copolymer in a similar mixed TFA/DCM solvent [58], quite different from the multiple morphologies observed in the diblock PPQ-b-PS. This implies that the vesicular morphology is thermodynamically a more stable aggregate than the flat disk, microtubules, or other morphologies in such rod-selective solvent system. Also, it demonstrates the importance of polymer architecture and the π–π interaction of the conjugated rod on the aggregated morphology.