Simplified Synthesis of Spiro-Bridged Ladder-Type Poly(p-phenylene)

In this study, a simplified route to synthesize soluble, spiro-bridged ladder-type poly(p-phenylene)s (spiro-LPPP) was developed. The new, simplified synthesis route for spiro-LPPP involves two reaction steps: a single-stranded precursor polymer containing diaryloylbenzene building blocks was obtained by the Suzuki reaction, followed by a subsequent twofold cyclization cascade using methanesulfonic acid to form the target spiro-LPPP. Spiro-LPPP shows a well-defined chemical structure, high molecular weight (M-n of 17,500 g/mol with a polydispersity index of 2.0), excellent thermal stability (5% weight loss at 370 degrees C), and good solubility in common organic solvents. Spiro-LPPP emits blue light (lambda(max,em) = 455 nm) with the high solution PL quantum yield (94%). The spectral properties of spiro-LPPP in the solid state are very similar to the solution properties, thus indicating a low degree of intermolecular aggregation. After annealing a thin film of spiro-LPPP to 120 degrees C in air for 3 to 24 h, its emission spectrum is unchanged, reflecting excellent thermooxidative stability. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5137-5143, 2009