Thermally stable and amorphous polyfluorene



Two-dimensional ladder-type polyfluorenes, which consist of polystyrene as the polymer backbone and polyfluorene as the light emitting component, were prepared through three synthetic pathways A, B, and C. In path A, the precursor polymer IP1 was obtained from the graft reaction of fluorene to units of poly(vinylbenzyl chloride) and then the ladder-type polymer P1 was prepared by coupling at the 2,7-position of fluorene with FeCl3 as an oxidizing agent in chloroform. In path B, IP2 was obtained from the graft reaction of lithiated 2,7-dibromofluorene and units of poly(vinylbenzyl chloride), and then P2 was prepared by the aryl-coupling of IP2 with a Ni-catalyst through the reductive polymerization. In path C, 4-(fluorenylmethyl)styrene was prepared by the reaction of 4-chloromethylstyrene and lithiated fluorene. Fluorene-attached syndiotatic polystyrene, IP3, was obtained in the polymerization of 4-(fluorenylmethyl)styrene with CpTiCl3-MAO catalyst, and for P3 oxidative coupling was further carried out. The polymers exhibited glass transition temperatures (Tg) of 422°C for P1, 404°C for P2, and 311°C for P3, and no melting endotherms were found. Syndiotaticity contributes the high glass temperature of P3 despite low molecular weight. Thermal decomposition temperatures at 5 wt % loss (Td) of 475°C for P1, 448°C for P2, and 365°C for P3 were observed. The fluorescence peaks of P1, P2, and P3 were observed at 401, 416, and 415 nm, respectively. For the emission spectrum of P3, no shoulder or peak regarding of aggregation of polyfluorene was observed. Syndiotacticity, due to the alternative configuration of fluorene, prevents a large Stoke's shift of the luminescence spectrum. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1335–1340, 2005