Polysiloxanes containing polyhedral oligomeric silsesquioxane groups in the side chains; synthesis and properties

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<ul><li><p>oties</p><p>anak</p><p>g diydrg pethy crolvmsnke</p><p>g beensilicon, andsuch aor wel isolat]. Becachanica</p><p>[1219]. POSS/polymer blend systems were also studied to improvethe polymers properties. However, POSSmolecules were also phase-separated and aggregated in polymer matrix. So the polymermembranes are not fully transparent and have optical defects even atlow POSS loading levels [14]. Therefore bulky groups such as phenyl,biphenyl, triphenyl, naphthalene, carbohydrate, cholesteric, andcyclohexyl groups also have been attached to the polysiloxanes</p><p>1,3,5,7,9,11,14-Heptacyclohexyltricyclo[,11]heptasiloxane-endo-3,7,14-triol (trisilanol-CyPOSS) was obtained from HybridPlastics Inc. and used without further purication. Allyltri-chlorosilane, 1-octene, and Platinum(0)-divinyl tetramethyldisi-loxane, Pt2[(CH2]CH)SiMe2OSiMe2(CH]CH2)]3, (Pt2(dvs)3, 2 wt%Pt solution in xylene) were used as received from Aldrich. Tolueneand tetrahydrofuran were distilled from Na/benzophenone andstored under dry nitrogen. All other reagents and solvents were</p><p>* Corresponding author. Tel.: 82 2 880 7070; fax: 82 2 888 1604.</p><p>Contents lists availab</p><p>ym</p><p>ls</p><p>Polymer 51 (2010) 22962304E-mail address: jongchan@snu.ac.kr (J.-C. Lee).dimensional stability, cross-linked polysiloxanes or copolymershaving siloxane units were prepare to improve their thermal/mechanical properties [711]. As an alternative approach to improvetheir thermal/mechanical properties, polysiloxane composites canbe prepared by mixing linear polysiloxanes with metal oxide llerssuch as zinc oxide, aluminum oxide, and ferric oxide, etc. or poly-hedral oligomeric silsequioxane (POSS) nanoparticles, but phaseseparation of these inorganic materials in the polymer matrix wasfound to be major problem to improve their physical properties</p><p>methods such as nuclear magnetic resonance, Fourier transforminfrared, gel-permeation chromatography, wide-angle X-ray scat-ting, differential scanning calorimetry, thermogravimetry analysis,rheometry, dynamic mechanical thermal analysis, and universaltesting machine are discussed in this paper.</p><p>2. Experimental</p><p>2.1. Materials1. Introduction</p><p>Polysiloxane derivatives have lonapplications including elastomers,adhesives, low dielectric materialsbecause of their unique propertiesoxygen permeability, low toxicity, posurface tension, outstanding electricaresistance, and biocompatibility [16derivatives have poor thermal/me0032-3861/$ see front matter 2010 Elsevier Ltd.doi:10.1016/j.polymer.2010.01.066used widely in manye oils, sealing agents,biomedical materials,s heat resistance, highttability, extremely lowing properties, chemicaluse linear polysiloxanel properties and low</p><p>through covalent bonding to improve their thermal/mechanicalproperties [2029].</p><p>In this work, POSS nanoparticles were covalently bonded topolysiloxanes to obtain organic/inorganic hybrid polymeric mate-rials with improved thermal/mechanical properties. These mate-rials were synthesized from hydrosilylation reactions of silanegroups (SiH) in poly(ethylhydrosiloxane) (PEHS) with allylcyclohexylPOSS (allylCyPOSS)/1-octene using platinum(0)-divinyltetramethyldisiloxane as a catalyst. The detailed synthetic proce-dures and characterization of these polymers using instrumentalPolysiloxanesPolysiloxanes containing polyhedral oligin the side chains; synthesis and proper</p><p>Hyun-Soo Ryu, Dong-Gyun Kim, Jong-Chan Lee*</p><p>Department of Chemical and Biological Engineering, Seoul National University, 599 Gw</p><p>a r t i c l e i n f o</p><p>Article history:Received 28 August 2009Received in revised form26 January 2010Accepted 31 January 2010Available online 6 February 2010</p><p>Keywords:HydrosilylationPolyhedral oligomeric silsesquioxane (POSS)</p><p>a b s t r a c t</p><p>Linear polysiloxanes havinwere prepared from the hPOSS and 1-octene usinplatinum(0)-divinyl tetramlinear polymer without ansoluble in various organic s10 mol%, free standing lpolysiloxane is not cross-li</p><p>Pol</p><p>journal homepage: www.eAll rights reserved.no, Gwanak-gu, Seoul 151-744, Republic of Korea</p><p>fferent amounts of polyhedral oligomeric silsequioxane (POSS) side groupsosilylation reaction of poly(ethylhydrosiloxane) with different amount oflatinum(0)-divinyl tetramethyldisiloxane as a catayst. 1-Octene andyldisiloxane were found to be very important for the preparation of theoss-linked structures. The linear polysiloxanes with POSS side groups areents. When the content of POSS-containing monomeric unit is larger thancan be prepared from a routine solution casting method, although thisd.</p><p> 2010 Elsevier Ltd. All rights reserved.meric silsesquioxane groups</p><p>le at ScienceDirect</p><p>er</p><p>evier .com/locate/polymer</p></li><li><p>er 5used as received from commercial sources, unless otherwisementioned. Trimethyl-terminated poly(ethylhydrosiloxane) (PEHS,viscosity at 25 C is 100 cSt on average.) was purchased fromGelest.The degree of polymerization of PEHS was estimated from the 1HNMR spectrum of PEHS by comparing the intensities of peaks from18 protons of the methyl groups at the chain end and that from oneproton of the hydrosilane (SiH) group in the backbone. The degreeof polymerization was about 370.</p><p>2.2. Measurements</p><p>1H nuclear magnetic resonance (1H NMR) spectrawere recordedusing 2wt% samples in CDCl3 on a Jeol (JNM-LA 300) (300MHz). TheFourier transform infrared (FT-IR) measurements were performedon a Perkin Elmer Spectrum 2000 FT-IR spectrometer in combina-tion with a deuterated triglycine sulfate (DTGS) detector using KBrpellets. In all cases, 16 scans at a resolution of 4 cm1 were used torecord the spectra. Weight-average molecular weight (Mw),number-average molecular weight (Mn), and molecular weightdistributions were measured by conventional gel-permeationchromatography (GPC) system equipped with a Waters 1515 Iso-cratic HPLC pump, aWaters 2414 refractive index detector, and a setofWaters Styragel columns (HR2 and HR4, 7.8 mm 300mm). GPCmeasurements were carried out at 30 C using THF as eluent witha ow rate of 1.0mL/min. The systemwas calibratedwith against tenknown polystyrene standards. The absolute molecular weights ofsome polymers were determined by GPC equipped with a multi-angle light scattering detector (GPC/MALS). THF was used aseluentwith a ow rate of 1.0mL/min. Detectors:Wyatt OPTILABDSPinterferometric refractive index detector and Wyatt miniDAWNlight scattering detector with a 20 mW semiconductor laser oper-ating at 690 nm. The glass transition temperature (Tg) and meltingtemperature (Tm) were determined using a TA Instruments differ-ential scanning calorimeter (DSC 2920) equipped with a DSC Cool-ing Can, which is allowed to cool down using liquid nitrogen, undera continuous nitrogen purge (60 mL/min). The heating rate was10 C/min. Pure indium was used to calibrate the instrument. Theglass transition temperatures were taken as the inection point inthe change in heat capacitywith temperature in the DSC curves. Thethermal stability of the polymers was analyzed by thermogravim-etry analysis (TGA) using a TA Instruments TGA 2050 undera continuous nitrogen purge of 60 mL/min. The samples wereheated from room temperature to 700 C with a uniform heatingrate of 10 C/min. The residual char yield was taken as the weightpercentage remaining at T 700 C. Wide-angle X-ray scatteringwas used to analyze the chemical structures of polymer samples.The measurements were carried out using the bending magnetbeam line 3C2 at the Pohang Light Source, Korea. X-rays of wave-length l 1.5406 monochromatized by a Si(111) double-crystalmonochromator were focused at the sample position by a toroidalpremirror. For high resolution transmission electron microscopy(HR-TEM) measurement, the 0.5 wt% solution of polymers in THFwas dropped onto carbon-coated copper grid. Just after vacuumevaporation of the solvent, thin polymer lms formed betweencopper grid lineswere observed from the transmittance for 300 keVusing TEM (JEM-3010, JEOL). The linear viscoelastic properties weremeasured with an ARES rheometer (TA Instruments). All of themeasurementswere performedwithin the linear viscoelastic range,using rotation rates of 0.1500 rad s1, where the dynamic shearstorage (G0) and shear loss modulus (G00) are independent of strain.Apparent shear viscosity [h (Pa s)], storage modulus [G0 (Pa)], andloss modulus [G00 (Pa)] were measured as a function of frequency inthe dynamic oscillatory mode. All of the rheological characteriza-tions were performed using a cone and plate with 25 mm diameter</p><p>H.-S. Ryu et al. / Polymandwith the gap between cone and plate being controlled precisely,with a typical value of 1.0 mm. Dynamic mechanical thermal anal-ysis (DMTA) was carried out in a nitrogen atmosphere witha Rheometric Scientic analyzer (MARK IV). Measurement of thetensile storage modulus (E0) and loss modulus (E00) of samples wereperformed at a frequency of 1 Hz andworking in single cantilever inthe temperature range from 70 to 100 C. The heating rate was3 C/min. The testing was performed using rectangular samplesmeasuring approximately 35 5.0 0.2 mm3. The exact dimen-sions of each sample were measured before the scan. The tensilestrength of the polymer lm was measured with dumbbell speci-mens according to theASTMD638 TypeV. The value for each samplewas taken as the median value of ve specimens. These tests werecarried out at room temperature on a universal tensile testingmachine (Lloyd instruments LR 10K) with a crosshead speed of50 mm/min.</p><p>2.3. Synthesis of 1-allyl-3,5,7,9,11,13,15-heptacyclopentylpentacyclo[,9.15,15.17,13]-octasiloxane(allylCyPOSS)</p><p>AllylCyPOSS was prepared using the method described byLichtenhan et al. as shown in Fig. 1 [30]. 1,3,5,7,9,11,14-Heptacyclo-hexyltricyclo[,11]heptasiloxane-endo-3,7,14-triol (trisilanol-CyPOSS) (24.34 g, 25mmol) and triethylamine (8.348 g, 82.5 mmol)were dissolved in distilled THF (200mL) and cooled in an ice bath. Asolution of allyl trichlorosilane (4.875 g, 27.5 mmol) in THF (25 mL)was added using an addition funnel to the cooled solution. Thereaction mixture was allowed to warm to room temperature andstirred for 24 h. Afterwards the reaction mixture was ltered toremove the Et3N$HCl byproduct. Volatiles were removed underreduced pressure at ambient temperature, and obtained yellowsolid was subsequently dissolved in aminimum amount of benzeneand precipitated into acetonitrile (5-fold excess) to eliminate theremaining byproduct completely. After ltration and drying undervacuum at room temperature, the yield of the obtained whitepowder was 97%.</p><p>1H NMR (CDCl3, ppm): 5.78 (m, 1H, SiCH2CH]CH2), 5.004.90(s, 2H, SiCH2CH]CH2), 1.75 (m, 35H, cyclohexylCH2), 1.61 (d, 2H,SiCH2CH]CH2), 1.25 (m, 35H, cyclohexylCH2), 0.76 (m, 7H,cyclohexylCH). 13C NMR (CDCl3, ppm): 132.6 (SiCH2CH]CH2),114.7 (SiCH2CH]CH2), 27.526.6 (cyclohexylCH2), 23.223.1(cyclohexylCH), 19.7 (SiCH2CH]CH2). FT-IR (KBr, cm</p><p>1): 3077(y, allylCH), 30002800 (y, CH2), 1646 (y, C]C), 1447 (d, CH2), 1108(y, T-type SiOSi), y: stretching mode; d: bending mode.</p><p>2.4. Synthesis of poly(ethylsiloxane)s containing CyPOSS andn-octyl side groups (PES#: # 0, 1, 4, 7, 10, 20, 25)</p><p>The abbreviation of poly(ethysiloxane)s containing CyPOSS and n-octyl in the side groups is PES#,where # is themol-% of allylCyPOSSgroupswith respect to the SiH groups in PEHS used in the synthesis.Fig.1 shows the synthetic routes for the preparation of PES#s and thesynthetic procedure is exemplied in the case of PES20 as follows.AllylCyPOSS (1.14 g,1.096mmol, 20mol% versus the SiH groups inPEHS) and PEHS (0.406 g, 5.480 mmol) were dissolved in freshlydistilled toluene (5.5 mL). The reaction mixture was stirred at roomtemperature for 5 min to obtain a homogeneous solution, and then0.05mL solution of Pt2(dvs)3 in xylene (2wt% Pt solution)was addedto the reaction mixture. After 1 h of stirring, 1-octene (0.590 g,5.261mmol,1.2 equiv. versus the remaining SiH groups) was addedto the reactionmixture and the reaction solutionwas stirred at roomtemperature for 5 days. The reactionwas monitored by 1H NMR andFT-IR. The disappearance of chemical shift (d 4.7 ppm) andstretching vibration (v 2160 cm1) contributed by the hydrosilane</p><p>1 (2010) 22962304 2297(SiH) group conrmed 100% conversion of SiH groups through the</p></li><li><p>ps (</p><p>H.-S. Ryu et al. / Polymer 51 (2010) 229623042298hydrosilylation reactions. The resulting polymer was obtained onprecipitation inmethanol three times andwashed several timeswithmethanol. The nal product was obtained after drying in a vacuumoven at room temperature for 2 days. Other PES#s (# 0, 1, 4, 7, 10,25)were obtainedwith the sameprocedure, except for the amount ofallylCyPOSS and 1-octene used (Table 1). The yields were alwaysabove 70%and100%conversions fromPEHSto PES#swere conrmed</p><p>Fig. 1. Synthetic routes for allylCyPOSS and polysiloxanes having POSS side grouby 1H NMR and FT-IR. The octyl and POSS content in polymers werecalculated by comparing the intensity of the peak at 1.88 ppm fromthe cyclohexyl group attached to the POSS cage (k in Fig. 2) and thatofthe peak at 0.55 ppm from the two methylene groups covalentlybonded at the silicone atom substituted with 1-octene (a and c inFig. 2). The POSS content in the polymer was similar to the allylCyPOSS used in the hydrosilylation reactions (Table 1). The physicalappearance of the isolated products changed from viscous liquid at07 mol% of POSS to powders at 20 mol% or greater POSS content. Aexible transparent lm about 200 mm thickness could be obtainedby casting from the THF solution of PES20 (Fig. 3(a)). The weight-average molecular weight (Mw) of the polymers measured fromGPC using polystyrene standards are in the range of 111000157000</p><p>Table 1Compositions of poly(ethylhydrosiloxane)s containing POSS and n-octyl side groups.</p><p>POSS (mol%) n-octyl content (mol%)a</p><p>Feeding In polymera Anti-Markovnikov addition</p><p>PEHSPES0 0 0 94.2 (94.2d)PES1 1 1.2 91.6 (92.7d)PES4 4 4.3 90.8 (94.9d)PES7 7 7.5 87.0 (94.1d)PES10 10 11.0 81.9 (92.0d)PES20 20 22.1 70.3 (90.2d)PES25 25 26.4 66.8 (90.8d)</p><p>a Calculated from 1H NMR.b Theoretical molecular weights from PEHS having 370 degree of polymerization.c Obtained from GPC using THF as solvent with respect to monodisperse polystyrened The numbers in parentheses are mol% among the octyl side groups.(Table 1), high enough to ignore the effect ofmolecularweight on thethermal properties of the polymers.</p><p>1H NMR (CDCl3, ppm): 1.75 (cyclohexylCH2), 1.46(SiCH2CH2CH2SiO3), 1.25 (SiCHCH3CH2, SiCHCH3(CH2)5CH3,SiCH2(CH2)6CH3, cyclohexylCH2), 0.94 (SiCH2CH3, SiCHCH3,CH2CH2CH3), 0.72 (cyclohexylCH), 0.65 (SiCH2CH2CH2SiO3), 0.51(CH CH SiO CH CH ). 13C NMR (CDCl , ppm): 34.0 (SiCHCH CH ),</p><p>PES#s), where the # is molar ratio of CyPOSS fed. (# 0, 1, 4, 7, 10, 20, and 25).3 2 2 2 2 3 3 2</p><p>32.3 and 29.8 (SiCHCH3CH2(CH2)3CH2, SiCH2(CH2)5CH2), 27.726.8 (cyclohexylCH2), 23.523.0 (CH2CH2CH3, cyclohexylCH),17.1 (Si(CH2)3SiO3), 16.3 (SiCH2(CH2)6CH3), 14.4 (CH2CH2CH3),8.48.1 (SiCH2CH3, SiCHCH3CH2), 6.8 (SiCH2CH3). FT-IR (KBr,cm1): 30002800 (y, CH2), 1462 (d, CH2), 1108 (y, T-type SiOSi), y: stretching mode;...</p></li></ul>