Morphology of organic semi-crystalline polymer after thermal nanoimprint

Abstract

The morphology of highly regular, semi-crystalline P3HT (poly 3-hexylthiophene-2.5-diyl) after thermal nanoimprint is studied and compared to that of its amorphous counterpart. Differential scanning calorimetry measurements of both materials provide the glass transition temperature (below room temperature) as well as the melting temperature (T _m ≈ 235 °C) and the crystallization temperature (T _c ≈ 200 °C) of the semi-crystalline polymer. Imprint experiments are performed at temperatures below and above the melting temperature of the crystallites. The samples imprinted with line structures in the range of 135–500 nm are investigated by scanning electron microscopy and transmission measurements. In agreement with T _m, the investigations indicate that the crystallites do not melt when semi-crystalline P3HT is imprinted below T _m. After imprint above T _m, no more indication of the crystallites is found. Furthermore, physical self-assembly only occurred after imprint beyond T _m with semi-crystalline P3HT, indicating a fully amorphous state. The morphology observed—the roughness of the surface within partly filled cavities when crystallites are present—correlates well with the results from optical measurements.