Poly(tetramethylsilarylenesiloxane) derivatives having diphenylfluorene (P1) or diphenyldibenzosilole (P2) moieties were prepared via polycondensation of the corresponding disilanol monomers, that is, 2,7-bis(dimethylhydroxysilyl)-9,9-diphenylfluorene (M1) and 2,7-bis(dimethylhydroxysilyl)-9,9-diphenyldibenzosilole (M2), respectively. P1 and P2 exhibited good solubility in common organic solvents. The glass transition temperatures (T g s) of P1 and P2 were determined by differential scanning calorimetry to be 125 and 119 1C, respectively. The melting temperature (T m ) of P1 was observed at 276 1C; however, the T m of P2 was not observed, indicating that the introduction of a dibenzosilole moiety decreased the crystallization tendency. The temperatures at 5% weight loss (T d5 s) of P1 and P2 were 539 and 520 1C, respectively, suggesting good thermostability of P1 and P2. Bathochromic and hyperchromic effects were observed in the absorption and fluorescence spectra by introducing a dimethylsilyl substituent onto diphenylfluorene and diphenyldibenzosilole skeletons. The replacement of diphenylfluorene by the corresponding diphenyldibenzosilole also led to bathochromic shifts. The fluorescence quantum yield (U F ) of P1 was lower than that of M1, probably because of the formation of aggregates; however, the U F of P2 was higher than that of M2, indicating a decrease in the tendency toward aggregation using a dibenzosilole skeleton.

KEY WORDS: Pyrene / Poly(tetramethylsilarylenesiloxane) / Heat-Resistant Polymer / Photoluminescence / Pyrene has been well-known to exhibit the good fluorescence property 1 and the unique emission based on its excited dimer in the fluorescence spectrum of the solution at a relatively high concentration (ca. 10 À3 mol/L) and/or of the solid state. Thus, various pyrene derivatives have been used for the emission moiety as an emitting fluorescence probe for biological analyst, electronics and photonics materials such as organic light-emitting diodes (OLEDs) and organic transistor, and so on.2 In addition, the incorporation of silyl substituents onto aromatic species has been reported to result in the high fluorescence quantum yield as well as in the red-shift of maximum absorption wavelength.3 If the silyl substituent is incorporated onto pyrene, the development of the highly efficient fluorophore is presumably promised. On the other hand, polysiloxanes having fluorophore moiety in the main chain have been reported to be obtained as oil products up to now. 4 Thus, the use of polysiloxane derivatives as polymeric OLED materials seems to be inadequate because of their low glass transition temperature (T g ) 5,6 inducing the formation of aggregates, even though the other properties of polysiloxanes such as good thermostability and stability against atomic oxygen 5,6 seem to be appropriate for the polymeric OLED materials. One of the methods for raising T g is incorporation of bulky and rigid moieties into the main chain.7 For example, the T g of poly(dimethylsiloxane) has been reported to be À123 C; 5 however, those of a series of poly(tetramethylsilarylenesiloxane) derivatives to be in the range from À52C to 156 C depending on the arylene moiety introduced. 7-9From these points of view, we report here the synthesis of poly-(tetramethyl-2,7-silpyrenylenesiloxane) (P1) via solution polycondensation of 2,7-bis(dimethylhydroxysilyl)pyrene (M1), as shown in Scheme 1. M1 was prepared by the hydrolysis of 2,7-bis(dimethylsilyl)pyrene (2), which had been obtained by the lithiation reaction of 2,7-dibromopyrene (1) 10 at À78 C followed by the addition of chlorodimethylsilane. M1 underwent polycondensation in chlorobenzene under reflux for 12 h to afford P1. The reaction solution was poured into acetone to isolate P1 as yellow precipitates. The structure of P1 was confirmed by 1 H and 13 C NMR spectroscopy, where each signal was consistently assigned ( Figure S1).P1 is soluble in common organic solvents such as tetrahydrofuran (THF), chloroform, and toluene. The number-average molecular weight (M n ) and the polydispersity index (M w =M n ) of P1 were estimated to be 43000 and 1.38, respectively, by the measurement of size-exclusion chromatography (SEC) of P1 in tetrahydrofuran (THF) eluent using polystyrene standards. The SEC profile of P1 indicated that the obtained polymer was unimodal and that the low-molecular-weight species as a cyclic dimer or trimer were almost completely removed by reprecipitation in acetone.The ther...

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Poly(tetramethyl-1,6-silpyrenylenesiloxane) derivative with phenyl groups on pyrenylene moieties (P1) was prepared via polycondensation of disilanol monomer, i.e. 1,6-bis(dimethylhydroxysilyl)-3,8-diphenylpyrene (M1). P1 exhibited the very high glass transition temperature (T g ) of 191°C. The temperature at 5% weight loss (T d5 ) of P1 was 482°C, indicating the relatively good thermostability of P1. P1 exhibited the bathochromic effect in the absorption and fluorescence spectra, indicating the expansion of p-conjugation by introducing phenyl groups onto pyrene skeleton as well as the r-p and r*-p* conjugation between pyrene and silyl moieties. In addition, P1 exhibited relatively weak excimer emission because of the inhibition of the excimer formation of pyrene skeleton by introduction of bulky phenyl groups onto pyrene skeleton. The fluorescence quantum yields (U F s) of M1 and P1 in chloroform were determined to be 0.46 and 0.37, respectively. It was revealed that M1 and P1 exhibited the higher fluorescence intensity than 1,6-diphenylpyrene, owing to the effect of the introduction of silyl moieties onto pyrene skeleton.

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