Phosphazene Backbones for Siloxanes and Organic Polymers
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Figure 1 Multifunctional Building Blocks for the Development of New Materials FG = Functional Group FG
FG
FG -111FG
GF
F
FG
FG
FG
FFG
4IIIIFG
FG
FG FG
atoms with FG in substituents
stars
F
FG FG
FG FG complex polyhedral structures
oligomeric or polymeric chain
In this work we focus on star systems with the inorganic cyclotriphosphazene core. We show the use of a commercially available molecule as a precursor for both star initiators in atom transfer radical polymerization (ATRP) and the sol-gel process.
129 Mat. Res. Soc. Symp. Proc. Vol. 576 ©1999 Materials Research Society
EXPERIMENTAL Materials: Laboratory grade reagents and solvents were used as received (Aldrich). 2,2,4,4,6,6Hexaxchlorocyclotriphosphazene was purified by recrystallization from hexanes. Preparation of the cyclotriphosphazene derivatives was carried out under an argon atmosphere with dry solvents. Physical measurements: IH and 3 'P NMR spectra were recorded in CDC1 on a 300 MHz Bruker spectrometer; 3 chemical shifts (8) given in ppm relative to TMS. Mass spectra were recorded on a Finnigan MAT LCQ mass spectrometer. Differential scanning calorimetric measurements (DSC) and thermogravimetric analyses (TGA) were performed on a Rheometric Scientific DSC Plus and TGA 1000, respectively. Heating rates were 10°C/min (DSC) and 20°C/min (TGA). BET measurements were performed by nitrogen adsorption on a Quantachrom Autosorb-l gas sorption system. Elemental analysis was carried out by Midwest Microlab, Indianapolis, IN. Cyclotriphosphazene derivatives: Synthesis of the 2,2,4,4,6,6-hexakis(4-(2-bromopropionyloxymethyl)phenoxy)cyclotriphosphazene for ATRP initiation (2) as well as the polymerization conditions and characterizations are described elsewhere [I]. Synthesis of 2,2,4,4,6,6-Hexakis(triethoxvsilylpropylamino)cyclotriphosphazene A solution of 5.00 g (14.4 rmmool) 2,2,4,4,6,6-hexachlorotriphosphazene in 20 ml toluene was added dropwise to a solution of 21.03 g (95 mmol) 3-aminopropyltriethoxysilane and 10.57 g (105 mmol) triethylamine in 50 ml toluene at room temperature over 20 min. The reaction mixture was heated under reflux for 4 h. During this time a white precipitate formed. The precipitate was removed by filtration. The solvent was evaporated from the filtrate and the 3aminopropyltriethoxysilane and triethylamine residues were evaporated under vacuum at 100 °C. The product was obtained as an opaque liquid in quantitative yield. Elemental analysis: calc. (found): C: 44.5 (39.89), H: 9.13 (9.08), N: 8.65 (7.04). 1H NMR (CDC13): 8 = 0.55 - 0.70 ppm (t, 12 H), 1.15 - 1.25 ppm (m, 60 H), 1.55 - 1.70 ppm (m, 12 H), 2.85 - 3.00 ppm, 3.75 - 3.90 ppm (q, 36 H). MS M+ = 1456.4 (calc. 1457.1). Sol-gel reactions: The sol-gel reactions were carried out by vigorous mixing of the precursor with ethanol in the ratios given in Table 1. After dilution the catalyst was added as an aqueous solution. The amount of water was calculated to be 3 equivalents per triethoxysilyl group. The solution was
again vigorously mixed and stored at room tem
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