In this study, a self-assembly technique assisted with thermoresponsive diblock copolymer poly(N,N-dimethylacrylamide)-b-poly(N-isopropylacrylamide) (PDMA-b-PNIPAM) is developed to fabricate crystalline microtubes of 2-(4′-((4′-vinylbenzyl)oxyl)phenyl)-4,5-diphenylimidazole (VPD). The as-prepared VPD microtubes are identified to have a hollow tubular structure with a rectangular cross section. All the obtained microtubes under optimal conditions have a uniform size of 220 nm in diameter, 20 nm in wall thickness, and 4.5 μm in length. Additionally, the length of the VPD microtubes can be readily controlled by adjusting the concentration of VPD. Furthermore, the VPD microtubes exhibit interesting size-dependent optical properties, of which the UV-vis absorption band shows an obvious red shift compared to that of the monomer. These results should be significant in triphenylimidazole derivative crystallization and their potential applications in optoelectronic devices.