cm0c02199_0002

(a) Chemical structure, (b) normalized UV–vis absorption spectra, and (c) cross-polarized optical microscopy (CPOM) images of DPP-T-TT and corresponding films with different thicknesses. The high-energy transition in b (blue background) has predominantly π–π* character delocalized across both the donor and acceptor units (blue region in a). The low energy transition (red background in b) is assigned to the π–π* transition of the DPP unit (red region in a). The 0–0 and 1–0 vibronic transitions of the π–π* DPP transition are centered at 820 and 750 nm, respectively. The inset shows magnification of the high-energy transition revealing an increase in its intensity with film thickness. The dark areas in the cross-polarized POM images in (c) highlight polymer chains that are aligned along one of the two polarized directions, while the bright regions are associated with chains aligned close to ±45° (the angle for maximum transmission light intensity). The 16 nm thick film (bottom image) shows polymer chains elongated in extended fibrelike domains. In contrast, the image of the 100 nm thick film shows short flakelike birefringence structures.

(a) Chemical structure, (b) normalized UV–vis absorption spectra, and (c) cross-polarized optical microscopy (CPOM) images of DPP-T-TT and corresponding films with different thicknesses. The high-energy transition in b (blue background) has predominantly π–π* character delocalized across both the donor and acceptor units (blue region in a). The low energy transition (red background in b) is assigned to the π–π* transition of the DPP unit (red region in a). The 0–0 and 1–0 vibronic transitions of the π–π* DPP transition are centered at 820 and 750 nm, respectively. The inset shows magnification of the high-energy transition revealing an increase in its intensity with film thickness. The dark areas in the cross-polarized POM images in (c) highlight polymer chains that are aligned along one of the two polarized directions, while the bright regions are associated with chains aligned close to ±45° (the angle for maximum transmission light intensity). The 16 nm thick film (bottom image) shows polymer chains elongated in extended fibrelike domains. In contrast, the image of the 100 nm thick film shows short flakelike birefringence structures.