Vertical Conducting Nanodomains Self-Assembled from Poly(3-hexyl thiophene)-Based Diblock Copolymer Thin Films

We have synthesized π-conjugated poly(3-hexyl thiophene)- block -poly(methyl methacrylate) (P3HT- b -PMMA) with a P3HT molecular weight of 11 kDa and a PMMA volume fraction of 0.53, which potentially has several organic electronic applications. Its phase-separation behavior was investigated for various thicknesses cast from organic solvents. When cast onto 300 nm thick SiO 2 dielectrics from toluene, in which the P3HT segments have limited solubility, the P3HT- b -PMMA films consist of nanofibrillar self-assemblies of laterally π-stacked P3HT chains. In contrast, the P3HT segments were found to be highly mobile in chlorobenzene, generating a typical phase-separation morphology consisting of vertically conducting P3HT nanodomains on these dielectrics. As the thickness of the cast films increased, however, the topmost surface becomes covered with π-conjugated nanofibrils that are laterally oriented with respect to the surface. Due to the anisotropic domain orientations of P3HT, top-gate organic field-effect transistors (OFETs) containing the P3HT- b -PMMA films exhibited enhanced electrical performance compared to bottom-gate OFETs.