Crystalline thin films of β-phase poly(9,9-dioctylfluorene)

The detailed structure of crystalline β-phase poly(9,9-dioctylfluorene) (PFO) films was studied by polarized optical measurements, transmission electron microscopy, and grazing-incidence X-ray diffraction. Crystalline β-phase PFO thin films were fabricated by a friction transfer technique and subsequent vapor treatment. Compared to the α-phase, the lattice parameters of the β-phase crystals shrank along the a-axis (film thickness direction) and elongated along the b-axis (side-chain direction), but the period along the c-axis (main-chain direction) remained nearly equal. These changes in molecular packing were consistent with a planar conformational change from the α-phase to the β-phase of PFO.