In order to gain insight into the photophysical properties of 4a and 4b, diffuse reflectance spectroscopies were carried out. Each polymer was dispersed to 1w% in magnesium oxide as dispersant and ground for 30 min prior to the measurements. The diffuse reflectance spectra of 4a and 4b are shown in Fig. with the absorption spectrum of 5 in dimethyl sulfoxide (DMSO) solution as a reference. Both spectra show two broad peaks that can be assigned as Soret bands (4a: 436 nm, 4b: 430 nm) and Q bands (4a: 667 nm, 4b: 664 nm). In comparison to the absorption spectrum of 5 (soret: 335 nm, Q: 634 nm) in DMSO, the Soret and Q bands of 4a were red-shifted by 101 and 33 nm (6.91 × 10 3 and 7.80 × 10 2 cm -1 ), respectively, indicating the extension of π-conjugation through polymerization. Similar results were observed for 4b (6.59 × 10 3 cm -1 for soret band and 7.13 × 10 2 cm -1 for Q band).