A class of amphiphilic rod-rod diblock copolymers composed of hydrophilic pi-conjugated poly(3-triethylene glycol thiophene) (P3(TEG)T) and hydrophobic rigid-rod-like poly(phenyl isocyanide) (PPI) was synthesized in one pot via mechanistically distinct, sequential block copolymerization with Ni(dppp)Cl-2 as a single catalyst. The hydrophilic P3(TEG)T homopolymer self-assembled into well-defined nanoparticles in THF and methanol with different dimensions and exhibited orange-light emission in THF and red-light emission in methanol. Interestingly, the resultant P3(TEG)T-b-PPI block copolymers were found to self-assembled into various well-defined supramolecular structures, such as nanofibrils in THF, micelles in methanol, and vesicles in 3/2 mixtures of THF and methanol. The assemblies of these block copolymers in solutions exhibited unique light emissions with the emission color spanned widely from orange red to blue depending on self-assembled morphology and solvents used. White light emission can be readily achieved through the control of self-assembled morphologies by variation on the solvent composition. Moreover, the light emissions of the block copolymers were completely reversible, demonstrating the tunable emissions were indeed ascribed to the morphological transitions of the block copolymer.