Crystalline and Noncrystalline Forms of Poly(9,9-diheptylfluorene)

The formation of ordered morphologies in poly­(9,9-diheptylfluorene) (PF7) was investigated using X-ray diffraction and grazing incidence X-ray diffraction. Two crystalline phases were found. The α-phase is orthorhombic with <i>a</i> = 2.60 nm, <i>b</i> = 2.25 nm, and <i>c</i> = 3.34 nm, and it is structurally very close to the α-phase in poly­(9,9-dioctylfluorene) (PF8). The γ-phase is monoclinic with <i>a</i> = 2.88 nm, <i>b</i> = 0.96 nm, and <i>c</i> = 1.68 nm, and the oblique angle is close to 90°. The γ-phase is the stable form in the bulk while the α-phase preferentially forms in thin films. Well-ordered and aligned crystalline films were produced from both good (toluene) and moderate (methylcyclohexane, MCH) solvent. Preparing films from MCH without annealing resulted in mesoscopic crystal with decreased order along the <i>a</i>-axis. This mesoscopic structure differs from the β-phase found in PF8 and is more related to the crystalline γ-phase. This difference may explain why mesoscopic PF8 has a phase transition into the α-phase, whereas the mesoscopic PF7 rather into the γ-phase

Suzuki Polycondensation: Polyarylenes à la Carte

This review draws a rather comprehensive picture of how Suzuki polycondensation was discovered in 1989 and how it was subsequently developed into the most powerful polymerization method for polyarylenes during the last 20 years. It combines insights into synthetic issues with classes of polymers prepared and touches upon aspects of this method's technological importance. Because a significant part of the developmental work was carried out in industry, the present review makes reference to an unusually large number of patents