Synthesis of an Inorganic–Organic Hybrid Material Based on Polyhedral Oligomeric Silsesquioxane and Polystyrene via Nitroxide-Mediated Polymerization and Click Reactions

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<ul><li><p>This article was downloaded by: [Universitat Politcnica de Valncia]On: 29 October 2014, At: 02:27Publisher: Taylor &amp; FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK</p><p>Designed Monomers and PolymersPublication details, including instructions for authors andsubscription information:</p><p>Synthesis of an InorganicOrganicHybrid Material Based onPolyhedral OligomericSilsesquioxane and Polystyrenevia Nitroxide-MediatedPolymerization and ClickReactionsDeniz Sinirlioglu a &amp; Ali Ekrem Muftuoglu ba Department of Chemistry, Fatih University,Buyukcekmece, Istanbul 34500, Turkeyb Department of Chemistry, Fatih University,Buyukcekmece, Istanbul 34500, Turkey;, online: 02 Apr 2012.</p><p>To cite this article: Deniz Sinirlioglu &amp; Ali Ekrem Muftuoglu (2011) Synthesis of anInorganicOrganic Hybrid Material Based on Polyhedral Oligomeric Silsesquioxane andPolystyrene via Nitroxide-Mediated Polymerization and Click Reactions, DesignedMonomers and Polymers, 14:3, 273-286</p><p>To link to this article:</p><p>PLEASE SCROLL DOWN FOR ARTICLE</p><p>Taylor &amp; Francis makes every effort to ensure the accuracy of all the information(the Content) contained in the publications on our platform. However, Taylor&amp; Francis, our agents, and our licensors make no representations or warrantieswhatsoever as to the accuracy, completeness, or suitability for any purposeof the Content. Any opinions and views expressed in this publication are theopinions and views of the authors, and are not the views of or endorsed byTaylor &amp; Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information. 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Terms &amp; Conditions of access and use can be found at</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>itat P</p><p>olit</p><p>cnic</p><p>a de</p><p> Val</p><p>nci</p><p>a] a</p><p>t 02:</p><p>27 2</p><p>9 O</p><p>ctob</p><p>er 2</p><p>014 </p><p></p></li><li><p>Designed Monomers and Polymers 14 (2011)</p><p>Synthesis of an InorganicOrganic Hybrid Material Basedon Polyhedral Oligomeric Silsesquioxane and Polystyrene via</p><p>Nitroxide-Mediated Polymerization and Click Reactions</p><p>Deniz Sinirlioglu and Ali Ekrem Muftuoglu </p><p>Department of Chemistry, Fatih University, Buyukcekmece, Istanbul 34500, Turkey</p><p>AbstractSynthesis of an inorganicorganic hybrid polymeric material composed of polystyrene and polyhedraloligomeric silsesquioxane (POSS) was carried out via nitroxide-mediated polymerization (NMP) andClick reaction. First, 4-chloromethyl styrene was polymerized in bulk at 125C using AIBN and 4-hydroxy-TEMPO as the initiator and stable free radical, respectively. Reaction of poly(4-chloromethylstyrene) (PCMS) with NaN3 in DMF yielded azide side-functional polystyrene. In the other step, acety-lene functional POSS was obtained by Steglich esterification of 3-hydroxypropylheptaisobutyl-POSS,C31H70O13Si8 (POSS-OH) and propiolic acid in the presence of N ,N -dicyclohexylcarbodiimide (DCC)and 4-dimethylamino pyridine (DMAP). Finally, Huisgen 1,3-dipolar cycloaddition between alkyne andazide functionalities afforded POSS side-chain functional polystyrene. The obtained hybrid polymer wascharacterized using 1H-NMR, 29Si-NMR, FT-IR, GPC and DSC. The DSC analysis showed that the Tg ofazide side-chain functional polystyrene (PS-N3) was enhanced by 14C upon POSS attachment. Koninklijke Brill NV, Leiden, 2011</p><p>KeywordsInorganicorganic hybrid polymeric material, POSS, NMP, Click reaction</p><p>1. Introduction</p><p>Inorganicorganic hybrid materials are a promising class of polymeric compos-ites, since hybrid properties can well be adopted by the careful adjustment of theinorganicorganic composition. The key parameter in tuning the macroscopic prop-erties is undoubtedly the extent of dispersion of the inorganic content in a givenpolymer matrix, i.e., how well the corresponding phases are mixed in the nanome-ter scale. Mechanical blending is a simple and inexpensive technique. However, thematerials thus obtained exhibit phase separation and aggregation of the inorganicmaterial, which limits the physical properties and, hence, the utility of the compos-ite [1].</p><p>* To whom correspondence should be addressed. Fax: (90-212) 866-3402; e-mail:</p><p> Koninklijke Brill NV, Leiden, 2011 DOI:10.1163/138577211X557558</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>itat P</p><p>olit</p><p>cnic</p><p>a de</p><p> Val</p><p>nci</p><p>a] a</p><p>t 02:</p><p>27 2</p><p>9 O</p><p>ctob</p><p>er 2</p><p>014 </p></li><li><p>274 D. Sinirlioglu, A. E. Muftuoglu / Designed Monomers and Polymers 14 (2011) 273286</p><p>One way to obtain nanocomposites is to blend polyhedral oligomeric silsesquiox-ane (POSS) groups with a polymer, since these nanocages with dimensions of about12 nm are supposed to be the smallest cage-like molecules [28]. However, a bet-ter approach is considerably the covalent linking of these POSS entities to polymerchains, since this will restrict POSS aggregation. In this manner, chain interac-tions and chain mobility are altered, possibly enhancing physical properties, suchas strength, modulus and thermal stability.</p><p>A current technique to achieve a POSS-incorporated polymer is the co-polymeri-zation of POSS carrying monomers with other appropriate monomers or the homo-polymerization of the sole POSS monomer provided that steric hindrance effect ofthe POSS constituent is avoided via the insertion of a spacer chain. Among the poly-mers obtained by this approach are polystyrene, polymethacrylate, polyurethanes,polysiloxane and epoxies [921].</p><p>Haddad et al. studied the mechanical properties of several POSS containingpolystyrenes and found that at temperatures above the glass transition the mod-uli were significantly higher depending on the type of corner alkyl groups ofPOSS [10]. Song et al. as well explored the thermal and mechanical properties ofPOSS-polystyrene nanocomposites. They found a 10C increase in the Tg value for3 wt% POSS content. They also observed simultaneous increase in tensile strength,elongation-at-break, elastic modulus and impact strength values when comparedwith pure polystyrene [13].</p><p>Recently, Click chemistry, coined by Sharpless and co-workers [22], has gainedincreasing interest in synthetic polymer chemistry due to its high selectivity andquantitative reaction yields besides its mild reaction conditions including toleranceto solvent, and a wide variety of functional groups. Among the Click reactions,Huisgen 1,3-dipolar cycloaddition occurring between alkyne and organic azide toafford 1,2,3-triazole has attracted a great deal of research activity [2333]. Whencombined with controlled polymerization methods, quite a number of architectures,such as graft co-polymers, stars, H-shape, hyperbranched and dendritic polymers,have been obtained [3443].</p><p>We herein report the synthesis of inorganic/organic hybrid material composed ofpolystyrene and heptaisobutyl-POSS via nitroxide-mediated polymerization (NMP)and Click reactions. By this approach, we present a model study on achieving poly-meric nanocomposites in a post-polymerization process based on highly selectiveHuisgen 1,3-dipolar cycloaddition reactions.</p><p>2. Experimental</p><p>2.1. Materials</p><p>3-Hydroxypropylheptaisobutyl-POSS (C31H70O13Si8, 95%), 2,2-Azobis(2-methylpropionitrile) (AIBN, 98%), 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4-hydroxy-TEMPO, 97%), N ,N ,N ,N ,N -pentamethyldiethylenetriamine(PMDETA, 99%), N ,N -dicyclohexylcarbodimide (DCC, 99%), 4-dimethylamino</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>itat P</p><p>olit</p><p>cnic</p><p>a de</p><p> Val</p><p>nci</p><p>a] a</p><p>t 02:</p><p>27 2</p><p>9 O</p><p>ctob</p><p>er 2</p><p>014 </p></li><li><p>D. Sinirlioglu, A. E. Muftuoglu / Designed Monomers and Polymers 14 (2011) 273286 275</p><p>pyridine (DMAP, 99%), copper(I) bromide and sodium azide were all purchasedfrom Aldrich and used as received. 4-Chloromethylstyrene (CMS) was purchasedfrom Aldrich and distilled over CaH2 under decreased pressure prior to use.Propiolic acid was purchased from Merck and used as received. Toluene anddichloromethane were purified by distillation over CaH2 under decreased pres-sure. Tetrahydrofuran (THF), methyl alcohol and N ,N -dimethylformamide werepurchased from Fluka and used without further purification.</p><p>2.2. Characterization</p><p>FT-IR spectra were obtained using a Bruker Alpha-P in ATR in the range of 4004000 cm1. 1H-NMR and 29Si-NMR spectra were recorded on a Bruker AM 400instrument in CDCl3. Chemical shifts are reported in ppm relative to TMS asinternal standard. Multiplicities are described using the following abbreviations:s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet and br = broad.Perkin Elmer JADE differential scanning calorimetry (DSC) was used to investi-gate the thermal transitions of the samples. The samples (approx. 10 mg) were filledinto aluminum pans and then heated to the desired temperature at a rate of 10C/minunder a nitrogen atmosphere. The glass transition temperatures were taken as themidpoint of the capacity change. In the measurements, Tg was taken from the sec-ond scans. Gel-permeation chromatography (GPC) measurements were performedon THF solutions of the polymers using an Agilent GPC 1100 instrument. Themeasurements were standardized against THF solutions of polystyrene standards.</p><p>2.3. Synthesis of Alkyne-Terminated Polyhedral Oligomeric Silsesquioxane(POSS-Alkyne)</p><p>POSS (0.1 g, 1.14 104 mol) was dissolved in CH2Cl2 (5 ml). Propiolic acid(11 l, 1.71 104 mol), DCC (38 mg, 1.82 104 mol) and DMAP (2.3 mg,1.82 105 mol) were added to the solution, which was then allowed to stir atroom temperature for 2 days. After several extractions with water, dichloromethanewas removed in a rotary evaporator. The final product was obtained in reddishcolor. It was kept 48 h in a vacuum oven at 40C for further use (78% yield).FT-IR (cm1): 3323 (CCH, alkyne asymmetric CH stretching), 2948 (aliphaticCH stretching), 2864 (aliphatic CH stretching), 2123 (CCH, alkyne asymmet-ric CH stretching), 1719 (ester C=O stretching), 1457, 1231 (asymmetric esterCO bending), 1095 (SiOSi bending). 1H-NMR (CDCl3, ppm, ): 4.084.02(t, 2H, SiCH2CH2CH2OCOCCH), 2.56 (s, 1H, SiCH2CH2CH2OCOCCH),1.821.75 (m, 2H, SiCH2CH2CH2OCOCCH), 1.62 (m, 1H, CH2CH(CH3)2)from R groups, 1.29 (d, 2H, CH2CH(CH3)2) from R groups, 0.91 (d, 6H,CH2CH(CH3)2) from R groups, 0.810.77 (t, 2H, SiCH2CH2CH2OCOCCH).29Si-NMR (CDCl3, ppm, ): Synthesis of p-Chloromethylstyrene (PCMS)</p><p>p-Chloromethylstyrene (4-vinylbenzyl chloride) (6.8 ml, 0.0483 mol), 4-hydroxy-TEMPO (97 mg, 5.62 104 mol) and AIBN (46 mg, 2.81 104 mol) were</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>itat P</p><p>olit</p><p>cnic</p><p>a de</p><p> Val</p><p>nci</p><p>a] a</p><p>t 02:</p><p>27 2</p><p>9 O</p><p>ctob</p><p>er 2</p><p>014 </p></li><li><p>276 D. Sinirlioglu, A. E. Muftuoglu / Designed Monomers and Polymers 14 (2011) 273286</p><p>placed into a Schlenk tube. After three freezepumpthaw cycles, the flask wasplaced in an oil bath at 125C, and kept there for 9 h. After the given time, themixture was diluted with THF, and the polymer was precipitated in a 10-fold ex-cess volume of methanol. The solid was then collected after filtration and dryingat 40C under reduced pressure overnight (conversion 58%). FT-IR T % (cm1):3026 (aromatic CH stretching), 2920 (aliphatic CH stretching), 2849 (aliphaticCH stretching), 1680, 1612 (aromatic C=C stretching), 1506, 1428, 822, 670.1H-NMR (CDCl3, ppm, ): 6.996.41 (br, 4H, from aromatic rings), 4.46 (br, 2H,CH2Cl). GPC: Mn 15 400 g/mol, PDI: 1.33.</p><p>2.5. Preparation of Azide Side-Functional Polystyrene (PS-N3)</p><p>PCMS (3 g, 0.01967 mol) and NaN3 (1.66 g, 0.0256 mol) were dissolved in 90 mlDMF in a Schlenk tube. The solution was allowed to stir at 25C for 2 days. Af-ter this period, DMF was removed in a rotary evaporator and the remaining solidwas dissolved in CH2Cl2. The solution was extracted three times with distilledwater to remove excess NaN3. Finally, the polymer was precipitated in 10-fold ex-cess methanol, collected by vacuum filtration, and kept 24 h at 50C in a vacuumoven for drying before analysis (87% yield). FT-IR T % (cm1): 3026 (aromaticCH stretching), 2925 (aliphatic CH stretching), 2864 (aliphatic CH stretching),2090 (azide N3 asymmetric stretching), 1680, 1607 (aromatic C=C stretching),1512, 1433, 820, 710. 1H-NMR (CDCl3, ppm, ): 6.906.48 (br, 4H, from aromaticrings), 4.17 (br, 2H, CH2N3). GPC: 16 100 g/mol; PDI: 1.34.</p><p>2.6. Synthesis of Polystyrene Containing Pendent POSS Cages via Click Reaction</p><p>PS-N3 (0.0129 g, 8 107 mol), POSS-alkyne (0.080 g, 8 105 mol), CuBr(0.115 g, 8 104 mol), PMDETA (115 l, 8 104 mol) and 30 ml CH2Cl2were placed in a reaction balloon with a magnetic bar. The mixture was bubbledwith nitrogen for 20 min and stirred for 2 days at room temperature. After thereaction, the mixture was further diluted with CH2Cl2 and passed through a basicalumina column to remove the catalyst. The product was precipitated in 10-foldexcess methanol 3 times, filtered and dried at 40C in a vacuum oven for 48 h (96%yield). FT-IR T % (cm1): 3023 (aromatic CH stretching), 2925 (aliphatic CHstretching), 2863 (aliphatic CH stretching), 1715 (ester C=O stretching), 1680,1607 (aromatic C=C stretching), 1517, 1438, 1349, 1248 (asymmetric ester CObending), 1113 (SiOSi bending), 810, 726. 1H-NMR (CDCl3, ppm, ): 7.57 (s,1H, from triazole ring), 6.906.48 (b, 4H, aromatic ring) 5.23 (s, 2H, CH2N3).29Si-NMR (CDCl3, ppm, ): 108.3, GPC: Mn 27 200 g/mol, PDI: 1.39.</p><p>3. Results and Discussion</p><p>Alkyne-terminated POSS (POSS-alkyne) was prepared by the esterification be-tween 3-hydroxypropyl heptaisobutyl-POSS and propiolic acid in the presenceof DCC/DMAP. This reaction, so-called Steglich esterification, is depicted inScheme 1.</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>itat P</p><p>olit</p><p>cnic</p><p>a de</p><p> Val</p><p>nci</p><p>a] a</p><p>t 02:</p><p>27 2</p><p>9 O</p><p>ctob</p><p>er 2</p><p>014 </p></li><li><p>D. Sinirlioglu, A. E. Muftuoglu / Designed Monomers and Polymers 14 (2011) 273286 277</p><p>Scheme 1. Synthesis of alkyne-terminated polyhedral oligomeric silsesquioxane (POSS-alkyne).</p><p>Figure 1. The 1H-NMR spectrum of alkyne-terminated POSS (POSS-alkyne).</p><p>The 1H-NMR spectrum of alkyne-POSS is shown in Fig. 1. The signals at4.08 (c), 2.55 (d), 1.82 (b) and 0.81 (a) ppm are assigned, respectively, to the res-onance of (SiCH2CH2CH2O, SiCH2CH2CH2OCOCCH, SiCH2CH2CH2,SiCH2CH2CH2) methylene, methine and methylene protons from POSS. Thesignals at 1.62 (k), 1.29 (m) and 0.91 (n) ppm belong to the resonance of(CH2CH(CH3)2,...</p></li></ul>


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