Polyethers possessing 9,9-diarylfluorene moieties in the main chain (F-PEs 3) were synthesized in 85-99% yields by the polycondensation of 9,9-bis(hydroxyaryl)fluorenes with alkyl ditosylates in the presence of cesium carbonate. Molecular weight of the F-PEs was dependent on the structure of the ditosylate 1; cyclohexyl-1,4-dimethylene (1a), 1,2-ethylene (1b), 1,3-trimethylene (1c), and 1,6-hexamethylene (1d). Higher molecular weight F-PEs (M n 32000-60000, M w 74000-160000) was obtained when longer alkyl chain ditosylates (1a and 1d) were used. The F-PEs showed good solubility toward various organic solvents such as toluene and high 5% weight loss temperature (T d5 : 424-447 C). The glass transition temperature of F-PEs (T g ) was ranging from 147 to 220 C. No melting point (T m ) was observed. F-PEs showed high water-resistance. The transmittance of F-PEs in film state (thickness: 21-32 mm) reached over 90% in the visible region. The F-PEs exhibited high refractive indices in a range of 1.62-1.66 at 590 nm in addition to sufficiently low birefringence values, probably due to the cardo structure of the fluorene moiety placed in the main chain. The structural dependence of dispersing ability to fullerene C 60 was investigated.KEY WORDS: Cardo Structure / Polyether / Refractive Index / Birefringence / Solubility / Thermal Stability / Processability / 9,9-Diarylfluorene-based polymers attract much attention due to the unique characteristics originated from the ''cardo'' structure as characterized often by the high refractive index and low birefringence.1-9 Such optical property is caused by the presence of many aromatic rings in the 9,9-diarylfluorene moiety which occupy the different planes to disturb the interchromophore packing, effectively decreasing the optical anisotropy. Meanwhile, such polymers also display excellent filler-dispersing ability [10][11][12] in addition to their high thermal stability, [13][14][15][16] high solubility, [17][18][19] and so on. [20][21][22][23][24][25] We have recently reported the special -interaction of the 9,9-diarylfluorene moiety in the matrix polymers toward -face of the carbon fillers.26 Although many polymers possessing 9,9-diarylfluorene moieties in the main chain have been developed to date, there is no study on polyethers. Polyethers are an important class of high performance engineering thermoplastics with a favorable combination of physical, mechanical, and chemical properties, other than processability, [31][32][33][34][35][36][37][38][39][40][41] and are easily synthesized usually by the polycondensation of diols and ditopic electrophiles. Polyethers with good optical and physical properties can be obtained, 42,43 if saturated alkyl group is introduced into the polymer main chain in addition to 9,9-diarylfluorene moiety, because the alkyl group often shows no optical anisotropy.Herein, we wish to disclose the synthesis and property of poly(alkyl aryl ether)s (F-PEs) containing 9,9-diarylfluorene moiety in the main chain, with emphasis on the effect of alkyl chai...