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Page 4 of 14 Shen et al. Soft Sci 2023;3:20 https://dx.doi.org/10.20517/ss.2023.10

Figure 1. The schematic of the preparation of PBED, P(BED-T), and P(BED-TT) films. BED-T: 2,5-bis(2,3-dihydrothieno[3,4-
b][1,4]dioxin-5-yl)thiophene; BED-TT: 2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)thieno[3,2-b]thiophene.

and 5 position on the Th ring . This indicates that the polymerization reaction mainly occurred at the α
[39]
position of the conjugated Th. Additionally, we observed absorption bands for the stretching vibration of
the C=C bond in the Th ring at 1,513 cm -1[40] . This suggests that the polymerization process did not involve
any ring-opening reactions. In summary, our results demonstrate that we have successfully produced
reliable PBEDs films.

The impact of introducing thienyl on the quality of PBEDs were evaluated by comparing their macroscopic
uniformity and micro-roughness. Figure 2A-C indicates that PBEDs exhibit excellent uniform continuity,
indicating that the addition of thienyl groups to the precursor does not affect the homogeneous continuity
of the polymer film. This finding suggests that the spray-spin coating polymerization technique is a highly
effective strategy for preparing high-quality films of precursor molecules with large conjugated rigid
structures. Furthermore, we used atomic force microscopy (AFM) to analyze the morphology of PBEDs
films and quantify the change in surface flatness caused by the introduction of thienyl groups. Figure 2D-F
depict the topography of PBED, P(BED-T), and P(BED-TT) films, respectively. No differences in their
aggregation at the topographic level were observed. Interestingly, the root-mean-square roughness (R ) of
ms
PBED, P(BED-T), and P(BED-TT) films were measured to be 49.4 nm, 26.9 nm, and 16.8 nm, respectively.
This indicates a decrease in the R of PBEDs film with the introduction of a larger conjugated structure of
ms
thienyl. The observed result is attributed to the introduction of larger conjugated structures, which increase
the effective conjugated length of polymer molecules and promote their planar packing. Additionally, the
non-covalent intermolecular and intramolecular interactions of O and S atoms of EDOT and Th or TT tend
to give the polymer molecules a one-dimensional planar structure. The line profile graphs and large
scanning areas of 80 μm × 80 μm, as shown in Figure 2G-I and Supplementary Figure 5, respectively,
support the results of the above analysis.