[reaction: see text] A twistacene, 6,8,15,17-tetraphenyl-1.18,4.5,9.10,13.14-tetrabenzoheptacene (3), was synthesized using a mild and novel bisbenzyne precursor. It was characterized by X-ray crystallography, NMR, UV-vis, and IR spectroscopies, as well as cyclic voltammetry and DFT calculations. The heptacene derivative possesses a nonpropeller twist topology and is unusually stable for a highly conjugated oligoacene. In addition, it is fluorescent, with a quantum efficiency of 15%. Distortion from planarity, mostly due to the phenyl substituents, causes only marginal changes in electronic properties and is beneficial for redox reversibility, which is required for efficient OLED devices.

A high-molecular-weight poly(2,5-dialkoxy-p-phenyleneethynylene) derivative has been prepared by the Heck reaction of 1,4-bis(2-ethylhexyloxy)-2,5-diiodobenzene and 1,4-diethynyl-2,5-dioctyloxybenzene. The highly luminescent polymer exhibits excellent solubility and can readily be processed into hi h optical-quality films. The weight-average molecular weight Mw was 240000 g -mol-, with a polydispersity index of 2.9. Thermal analysis revealed a glass transition around 90°C, and an onset of chemical crosslinking at 130°C. The high Mw and the remarkable solubility enabled the preparation of liquid crystalline solutions of the new PPE.

Within the wealth of hydrocarbon polymers, poly(p‐phenylene alkylene)s (“alkarotics”) hold a special position since they have been a long forgotten class of hydrophobic polymers. This is somewhat surprising, since the cornerstones of this polymer family cover extremely broad materials properties and the few known representatives attract attention with very favorable characteristics. In the course of this article, four new representatives of this family are presented. Whereas poly(p‐phenylene octylene) (PPPO; 90°C), poly(p‐phenylene hexylene) (PPPH; 120°C) and poly(p‐phenylene propylene) (PPPPr; 110–130°C) have surprisingly low melting temperatures, the highly crystalline poly(p‐phenylene butylene) (PPPB), melting between 200 and 225°C, meets many of the requirements that are essential for a novel, hydrophobic, processable, engineering polymer. In connection with the efforts to tailor the melting temperature of these polymers, a simple, semi‐empirical methodology to estimate melting temperatures of unknown representatives of homologous series of polymers was developed and verified. By means of this approach, the melting temperatures of PPPH and PPPB could be predicted with remarkable accuracy. In addition, it was shown that the method is not restricted to the present alkarotic polymers, but it seems to have a rather broad range of applications as shown by the successful description of the polymer series, including various liquid‐crystalline hydrocarbon polymers and different polyamides.

Acyclic diene metathesis (ADMET) polymerization was used as a new synthetic route to a class of processable, hydrophobic, and crystalline polymers which contain only aromatic and aliphatic hydrocarbon units in their backbone. Poly(p-phenylene octylene) (PPPO), as a first example, was prepared by the ADMET polymerization of 1,4-bis(pent-4-ene)benzene, followed by the catalytic reduction of the resulting unsaturated polymer. The weight-average molecular weights of the polymers obtained with this method were in the range of 13 000−25 000. Poly(p-phenylene octylene) was found to be highly soluble in common solvents and to have a melting temperature of around 90 °C, which enabled melt processing into fibers and films without decomposition. Wide-angle X-ray diffraction and annealing experiments on PPPO revealed two different crystal modifications. The polymer, as precipitated from the reaction mixture, predominantly forms the kinetically preferred modification α, while the annealing of pristine PPPO almost exclusively leads to the thermodynamically more stable modification β.