Synthesis and characterization of poly(methyl methacrylate-co-polyhedral oligomeric silsesquioxane) hybrid nanocomposites

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<ul><li><p>Synthesis and characterization of</p><p>poly(methyl methacrylate-co-polyhedral</p><p>oligomeric silsesquioxane) hybrid nanocomposites</p><p>Ben Hong Yang a,c, Hong Yao Xu a,b,*, Cun Li a, Shan Yi Guang b</p><p>a School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039, ChinabCollege of Material Science and Engineering &amp; State Key Laboratory of Chemical Fibers and Polymeric Materials,</p><p>Donghua University, Shanghai 200051, ChinacDepartment of Chemical and Material Engineering, Hefei University, Hefei 230022, China</p><p>Received 6 March 2007</p><p>Abstract</p><p>A novel poly(methyl methacrylate-co-polyhedral oligomeric silsesquioxane) hybrid nanocomposite was synthesized by free</p><p>radical polymerization and characterized by 1H NMR, 29Si NMR, and TGA technologies. Compared with PMMA homopolymer,</p><p>the nanocomposite has better thermal stability.</p><p># 2007 Hong Yao Xu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.</p><p>Keywords: Poly(methyl methacrylate); Polyhedral silsesquioxane; Nanocomposite</p><p>Synthetic polymers have played an important role in our daily lives for many years. However, the inherent</p><p>drawbacks like weak mechanical strength and low thermal stability often restrict their further applications.</p><p>Polyhedral oligomeric silsesquioxane (POSS) is a nanosize compound that has an inorganic cube-like core (Si8O12)</p><p>with its eight corners connected by organic groups (R) [1]. The R groups can be reactive ones, which make POSS</p><p>molecules to be excellent monomers for preparing inorganicorganic hybrid nanocomposites [29]. In these</p><p>nanocomposites, the nanosize POSS moieties are chemically bonded to the polymeric matrix and homogeneously</p><p>dispersed at molecular level, thus effectively improving the thermal and mechanical properties of these hybrid materials.</p><p>In this paper, a novel poly(methyl methacrylate-co-octavinyl polyhedral oligomeric silsesquioxane) (PMMA</p><p>OVPOSS) hybrid nanocomposite was synthesized by common free radical polymerization. The TGA results revealed</p><p>that the resulting PMMAOVPOSS nanocomposite has better thermal stability than PMMA homopolymer.</p><p>1. Experimental</p><p>The PMMAOVPOSS nanocomposite was prepared via free radical polymerization technique as shown in Scheme</p><p>1. In a typical reaction, 9.92 mmol of methyl methacrylate and 0.08 mmol of octavinyl-POSS (OVPOSS) in 5 mL</p><p>www.elsevier.com/locate/cclet</p><p>Chinese Chemical Letters 18 (2007) 960962</p><p>* Corresponding author.</p><p>E-mail address: hongyaoxu@163.com (H.Y. Xu).</p><p>1001-8417/$ see front matter # 2007 Hong Yao Xu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.doi:10.1016/j.cclet.2007.05.041</p></li><li><p>dried 1,4-dioxane were stirred for 8 h at 70 8C under a nitrogen atmosphere, using the AIBN initiator. The product wasthen added dropwise into heated ethanol under vigorously agitation to dissolve the unreacted OVPOSS and methyl</p><p>methacrylate monomers and to precipitate the nanocomposite. The precipitated product was purified with 1,4-dioxane/</p><p>ethanol and characterized by 1H NMR and 29Si NMR spectroscopies. The thermogravimetric analysis was performed</p><p>in nitrogen flow at a ramp rate of 10 8C/min.</p><p>2. Results and discussion</p><p>Fig. 1 shows the 1H NMR spectra of OVPOSS, PMMA and PMMAOVPOSS. For pure OVPOSS macromer, the</p><p>absorption band of vinyl protons is observed at d 6.0 ppm as multiple peaks. For pure PMMA, the resonance band atd 3.6 ppm is attributed to the methyl proton connected to the ester group, and bands at d 1.42.0 and 0.71.1 ppmbelong to the resonance absorptions of methylene and the pendant methyl protons, respectively. The PMMA</p><p>OVPOSS nanocomposite displays both absorptions at d 3.6, 1.42.0 and 0.71.1 ppm like PMMA and at d 6 ppm as</p><p>OVPOSS, indicating that the OVPOSS cages have been incorporated into the polymeric matrix.</p><p>Fig. 2 shows the 29Si NMR spectra of both pure OVPOSS macromer and PMMAOVPOSS nanocomposite. For</p><p>pure octavinyl-POSS, there is only one resonance peak at d79.3 ppm. For PMMAOVPOSS, two resonance peaks atd79.2 and65.3 ppm are attributed to the silicon atoms connected to the unreacted and the reacted vinyl groups onthe OVPOSS cages, respectively. The relative intensity of the resonance peaks at d79.2 and65.3 ppm implies thatmost of the vinyl groups on OVPOSS have participated in the polymerization.</p><p>Fig. 3 displays the TGA thermograms of pure PMMA, PMMA/OVPOSS blend and PMMAOVPOSS (0.85 mol%of OVPOSS) nanocomposite. The PMMA homopolymer undergoes four-step degradations, and its Tdec (the</p><p>temperature of 5% weight loss) is 192 8C. The PMMA/OVPOSS blend shows three-step degradation with a Tdec of177 8C. While the PMMAOVPOSS nanocomposite only has one-step degradation and the Tdec is 256 8C, which is64 8C higher than the mother polymer PMMA and 79 8C larger than PMMA/OVPOSS blend. It reveals that PMMAOVPOSS nanocomposite has better thermal stability than PMMA and PMMA/OVPOSS blend, implying that the</p><p>B.H. Yang et al. / Chinese Chemical Letters 18 (2007) 960962 961</p><p>Scheme 1. Synthesis of PMMAOVPOSS nanocomposite.</p><p>Fig. 1. 1H NMR spectra of PMMAOVPOSS, PMMA, and OVPOSS.</p></li><li><p>incorporation of POSS into PMMA matrix by copolymerization is a good way to improve the thermal property of</p><p>PMMA.</p><p>Acknowledgments</p><p>This research was financially supported by the National Natural Science Foundation of China (Nos. 50472038 and</p><p>90606011), Program for New Century Excellent Talents in University (NCET-04-0588) and the Excellent Youth Fund</p><p>of Anhui Province (No. 04044060).</p><p>References</p><p>[1] R.H. Baney, M. Itoh, A. Sakakibara, T. Suzuki, Chem. Rev. 95 (1995) 1409.</p><p>[2] T.S. Haddad, J.D. Lichtenhan, Macromolecules 29 (1996) 7302.</p><p>[3] H.Y. Xu, S.W. Kuo, J.S. Lee, F.C. Chang, Polymer 43 (2002) 5117.</p><p>[4] J.D. Lichtenhan, Y.A. Otonari, M.J. Carr, Macromolecules 28 (1995) 8435.</p><p>[5] J. Pyun, K. Matyjaszewski, Macromolecules 33 (2000) 217.</p><p>[6] B.X. Fu, B.S. Hsiao, S. Pagola, J. Lichtenhan, J. Schwab, Polymer 42 (2001) 599.</p><p>[7] H.Z. Liu, S.X. Zheng, K.M. Nie, Macromolecules 38 (2005) 5088.</p><p>[8] H.Y. Xu, S.W. Kuo, C.F. Huang, F.C. Chang, J. Appl. Polym. Sci. 91 (2004) 2208.</p><p>[9] H.Y. Xu, B.H. Yang, J.F. Wang, S.Y. Guang, C. Li, Macromolecules 38 (2005) 10455.</p><p>B.H. Yang et al. / Chinese Chemical Letters 18 (2007) 960962962</p><p>Fig. 2. 29Si NMR spectra of pure PMMAOVPOSS and OVPOSS.</p><p>Fig. 3. TGA thermograms of pure PMMA, PMMAOVPOSS copolymer and PMMA/OVPOSS blend.</p><p>Synthesis and characterization of poly(methyl methacrylate-co-polyhedral oligomeric silsesquioxane) hybrid nanocompositesExperimentalResults and discussionAcknowledgmentsReferences</p></li></ul>