Highly Branched Polyphenylenes with 1,3,5-Triphenylbenzene Fragments via Cyclocondensation of Acetylaromatic Compounds and Ni0-Catalyzed Dehalogenation:  Synthesis and Light Emission

• Published in: Macromolecules Vol. 36; no. 22; pp. 8353 - 8360
• Main Authors: Khotina, Irina A, Shmakova, Olga E, Baranova, Diana Yu, Burenkova, Natalia S, Gurskaja, Anastasia A, Valetsky, Peter M, Bronstein, Lyudmila M
• Format: Journal Article
• Language: English
• Published: American Chemical Society 04.11.2003
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma0347114

Highly branched photoluminescent polyphenylenes (PP) containing 1,3,5-triphenylbenzene (TPB) fragments were prepared via combination of cyclocondensation of acetylaromatic compounds and Ni0-catalyzed dehalogenation. To develop optimal conditions for cyclocondensation of acetylaromatic compounds, we studied a model reaction of 1,3,5-triphenylbenzene formation using different solvents and catalysts. The maximum 85% yield of TPB was achieved using H2SO4 as a catalyst in ethanol−toluene medium at 50 °C for 5 h. Cyclocondensation polymerization of 4,4‘-diacetyl diphenyl ether or 4,4‘-diacetylbenzene in the presence of equimolar amounts of acetophenone (in the optimal conditions with respect to the soluble polymer yield) did not produce photoluminescent PP due to various defects in the polymer chain. Defect-free PP with starlike fragments were synthesized using Ni0-catalyzed polymerization of aromatic bromides obtained by modification of 1,3,5-tri(p-bromophenyl)benzene. The molecular weights of the polymers were 6700 and 8600 Da. The maximum photoluminescence in solution (quantum yield of 96%) was obtained for the highly branched polymer with starlike TPB fragments, bearing no Br or acetyl groups. The PP of this kind also show very bright fluorescence in the solid state under UV irradiation at 360 nm so they can be considered as promising materials for OLED applications.