苯乙炔基封端的聚(硅乙炔-4,4‘-二苯醚)的合成和性能

Synthesis and properties of phenyl acetylene terminated poly (silyleneethynylene-4,4’-phenylethereneethynylene)s1Xu Jinfeng Shen Yongjia*Institute of Fine Chemicals Institute of Fine ChemicalsEast China University of Science and Technology East China University of Science and Technology Shanghai 200237, P. R. China Shanghai 200237, P. R. China eleven_xu@ yjshen@Wang ChengyunInstitute of Fine ChemicalsEast China University of Science and TechnologyShanghai 200237, P. R. Chinacywang@AbstractTwo kinds of phenylacetylene-terminated poly(silyleneethynylene-4,4′-phenylethereneethynylene)s, {C6H5-C≡C-[Si(R)2-C≡C-C6H4-O-C6H4-C≡C]n-C6H5} wherein R represents methyl or phenyl, were synthesized by condensationreaction between dichlorosilanes and 4, 4′-diethynyldiphenyl ether using organicmagnesium reagents. The polymers were characterized by NMR, IR, gel permeationchromatography, thermogravimetric analysis, and differential scatteringcalorimetries.Keywords: phenyl acetylene, polysilanes, gel permeation chromatography,thermogravimetric analysis, differential scattering calorimetries1 IntroductionOrganosilicon polymers have received a great deal of attention because of their alternating arrangement in an organosilicon unit, π-electron system, and potential applications as advanced materials such as, ceramics precursors[1], organic semiconductors[2], hole-transporting materials[3], thermally stable polymers[4], liquid crystalline polymers[5]. In addition, polymers having ethynylene units in the π-electron system have been extensively studied[6]. An example includes the synthesis of poly [(hydrosilylene) ethynylene (phenylene) ethynylene]s with excellent heat-resistant and flame-resistant properties, reported by Itoh and his co-workers[7], which is fusible and soluble in most common organic solvents. In this paper, we report the synthesis of two kinds of new resins1 Support by the Specialized Research Fund for the Doctoral Program of Higher e ducation (No.20030251001)* Corresponding authorphenylacetylene-terminated poly(silyleneethynylene-4, 4′-phenyl etherene ethynylene)s (1a and 1b , Figure 1), which are highly heat-resistant, low moisture sensitive and highly processable polymers. Selecting appropriate monomers can further enhance specific and desirable properties.Si OSi R RR Rn1a R=Me1b R=PhFigure 1: phenyl acetylene terminated poly (silyleneethynylene-4,4′-phenylethereneethynylene)s2 Experimental SectionMaterials: All chemicals and solvents were purchased from Shanghai Reagent Company and distilled or dried when necessary using standard procedures.Instrument: IR spectra were recorded on a Nicolet spectrophotometer. 1H NMR spectra were obtained on a Bruker AVANCE 500 spectrometer operating at 500 MHz: chemical shifts were quoted downfield of TMS. Molecular weight distribution curves of polymers were determined by Gel Permeation Chromatography (GPC) using 105, 104 and 103 Å µ-Styragel columns at 35°C. Polymers were eluted with tetrahydrofuran and detected using a refractive detector (Waters. Model R4000). Polystyrene standards of molecular weight ranging from 233000 to 750 were used for calibrating GPC columns for hydrodynamic volume versus elution volume. Differential scattering calorimetries (DSC) were performed on a DSC50 Shimadzu (10°C/min). The thermo gravimetric were analysed on a Setaran TGA24 (10°C/min).The basic reactions used for the synthesis of phenylacetylene-terminated poly (silyleneethynylene-4, 4′-phenylethereneethynylene)s are shown in Scheme 1.1a R=Me 1b R=PhScheme 1: basic reactions used for the synthesis of phenyl acetylene terminated poly(silyleneethynylene-4, 4′-phenylethereneethynylene)sGeneral synthesis for phenylacetylene-terminated poly(silyleneethynylene-4, 4′-phenylethereneethynylene)s was condensation reaction using organic magnesium reagents. All the operations were carried out under inert atmosphere conditions using pure argon, solvents and reagents were dried and distilled.Synthesis of phenylacetylene-terminated poly(dimethylsilyleneethynylene-4, 4′-phenylethereneethynylene) s (1a)Ethyl bromide (21.8g, 0.2mol) in tetrahydrofuran (50ml) was added dropwise to a stirred mixture of magnesium powder (5.76g, 0.24mol) in tetrahydrofuran (50ml) at room temperature for 30min. The reaction mixture was heated at reflux for 2h, followed by the dropwise addition of a solution ofbis-(4-ethynyl-phenyl) ether (17.44g, 0.08 mol) and phenylacetylene (2.04g, 0.02mol) in tetrahydrofuran (50ml), After another one-hour reflux, the mixture turned from a clear solution to a suspension. Then dimethyldichlorosilane (11.61g, 0.09mol) in tetrahydrofuran (50ml) was added dropwise, and stirred at reflux for another 1 h. The reaction mixture was cooled, then treated with 0.1M HCl (50ml) and separated into two layers, the organic phase was isolated and the solvent was evaporated under reduced pressure. The residue was extracted by chloroform, neutralized with 0.1M NaOH, washed with water and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, to give 23.3g resin 1a(II) (yield 94%) as a pale yellow viscous oil. Mw=2430 (Mw/Mn=1.67). 1H NMR (500MHz, CDCl3): (ppm). 0.15 (Me2Si), 6.85~7.38(phenylene). IRν(neat) 2157 cm-1(C≡C).Synthesis of phenylacetylene-terminated poly(diphenylsilyleneethynylene-4, 4′-phenylethereneethynylene) s (1b)Using essentially the same procedure and employing diphenyldichlorosilane (22.77g, 0.09mol), 33.0g resin 1b(V) (yield 92%) was obtained as a pale yellow viscous oil. Mw=3045 (Mw/Mn=1.82). 1H NMR (500MHz, CDCl3): (ppm). 6.85-7.54( phenylene). IR ν(neat) 2150 cm-1(C≡C).3 Results and DiscussionPhenyl acetylene-terminated poly (silyleneethynylene-4, 4′-phenylethereneethynylene)s, {C6H5-C≡C-[Si(R)2-C≡C-C6H4-O-C6H4-C≡C]n-C6H5} wherein R represents methyl or phenyl, were synthesized by condensation reaction between dichlorosilanes and 4, 4′-diethynyldiphenyl ether using organic magnesium reagents. These reactions proceeded smoothly. Chemical structures of the polymers have been determined by 1H NMR. They are in good agreement with the desired structures. The addition of phenylacetylene to 4, 4′-diethynyldiphenyl ether allows a perfect control of the molecular masses of the macromoleculars shown in Table 1 and Table 2.Table 1: the molecular masses of 1a controlled by phenyl acetyleneindex No. The mol. ratio of phenyl acetylene to 4,4′-diethynyldiphenyl ether Mn Mw PolydispersityⅠ0 2131 3452 1.62Ⅱ1:4 1455 2430 1.67Ⅲ1:1 980 1564 1.60Table 2: the molecular masses of 1b controlled by phenyl acetyleneNo. The mol. ratio of phenyl acetylene to 4,4′-diethynyldiphenyl etherMn Mw Polydispersity indexIV 0 3068 5827 1.90 V 1:4 1341 2200 1.64 VI1:1 1028 1543 1.50By Gel permeation chromatography (GPC), molecular mass distributions of some polymers weredetermined. As presented in Figure 2, polymer IV possesses monomodal molecular mass distribution, whereas polymer V shows multimodal molecular mass distribution.Figure2: GPC curves of IV and VThermal properties of II and V were examined by TGA–DTA in nitrogen. Their Td5 and final weight loss at 1000°C are listed in Table 3. As expected, the materials obtained from the polymers exhibited excellent heat-resistant properties in nitrogen. In particular, V showed higher Td5 and lower weight loss at 1000°C (Table 3) than those of II . This is probably due to the larger number of Si-Me bonds in a repeating unit that are relatively unstable as indicated by the smaller bond dissociation energy of Si-Me (318 kJ/mol) than that of Si-Ph (358 kJ/mol) [8].Table 3: TGA of polymers in nitrogenTGA in nitrogen apolymersTd5 (°C) b Weight loss (%) cII 603 23V 625 19a. At a rate of 10°C /min from 25 to 1000°C.b. Temperature resulting in 5% weight loss based on the initial weight.c. Total weight loss at 1000°C.DTA of V revealed a sharp exothermic peak at 200–220°C in Figure 3. This signal above 200°C iscuring temperature. Presumably, cross-linking reactions of polymers occurred at this temperature,which would be responsible for the high heat resistance of these polymers. In fact, when polymer washeated at 210°C in nitrogen, the polymers became insoluble.Figure 3: TGA-DAT of VThe IR spectrum of V after being heated revealed a decrease of the absorption band at around 2150cm-1due to the C≡C bond stretching frequency (Figure 4, 5), indicating that some cross-linking reactions[9].Figure 4: IR spectra of polymer VFigure 5: IR spectra of polymer V after heating at 220°C for 30min in nitrogenA c k n o w l e d g m e n t sWe thank the foundation of the Specialized Research Fund for the Doctoral Program of Higher education (No. 20030251001) for financial support.References[1] Puerta AR, Remsen EE, Bradley MG, Sherwood W, Sneddon LG. (2003)Synthesis and Ceramic ConversionReactions of 9-BBN-Modified Allylhydridopolycarbosilane: A New Single-Source Precursor to Boron-Modified Silicon Carbide. 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