Ring‐Banded Spherulitic Crystals of Poly(3‐butylthiophene) via Controlled Solvent Evaporation

The preparation of ring‐banded spherulites in poly(3‐butylthiophene) via controlled solvent evaporation of solution‐cast films is reported. The spherulites display unusual concentric ring‐banded structures under both polarized and unpolarized lights. The size of the ring‐banded spherulites is 300 ± 100 µm in diameter and the periodicity of the bands is 15 ± 2 µm. The periodic bands of the spherulite consist of alternating ridge and valley surface patterns and the crystalline lamellae in the bands are more or less parallel to the radial growth direction of the spherulites. Local lamellar bending and branching are observed analogous to that of classical non‐conjugated polymers. A possible diffusion‐induced rhythmic growth mechanism is proposed to interpret the formation of periodic banding of the spherulite.