Synthesis and characterization of

poly(methyl methacrylate-co-polyhedral

oligomeric silsesquioxane) hybrid nanocomposites

Ben Hong Yang a,c, Hong Yao Xu a,b,*, Cun Li a, Shan Yi Guang b

a School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039, Chinab College of Material Science and Engineering & State Key Laboratory of Chemical Fibers and Polymeric Materials,

Donghua University, Shanghai 200051, Chinac Department of Chemical and Material Engineering, Hefei University, Hefei 230022, China

Received 6 March 2007

Abstract

A novel poly(methyl methacrylate-co-polyhedral oligomeric silsesquioxane) hybrid nanocomposite was synthesized by free

radical polymerization and characterized by 1H NMR, 29Si NMR, and TGA technologies. Compared with PMMA homopolymer,

the nanocomposite has better thermal stability.

# 2007 Hong Yao Xu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Keywords: Poly(methyl methacrylate); Polyhedral silsesquioxane; Nanocomposite

Synthetic polymers have played an important role in our daily lives for many years. However, the inherent

drawbacks like weak mechanical strength and low thermal stability often restrict their further applications.

Polyhedral oligomeric silsesquioxane (POSS) is a nanosize compound that has an inorganic cube-like core (Si8O12)

with its eight corners connected by organic groups (R) [1]. The R groups can be reactive ones, which make POSS

molecules to be excellent monomers for preparing inorganic–organic hybrid nanocomposites [2–9]. In these

nanocomposites, the nanosize POSS moieties are chemically bonded to the polymeric matrix and homogeneously

dispersed at molecular level, thus effectively improving the thermal and mechanical properties of these hybrid materials.

In this paper, a novel poly(methyl methacrylate-co-octavinyl polyhedral oligomeric silsesquioxane) (PMMA–

OVPOSS) hybrid nanocomposite was synthesized by common free radical polymerization. The TGA results revealed

that the resulting PMMA–OVPOSS nanocomposite has better thermal stability than PMMA homopolymer.

1. Experimental

The PMMA–OVPOSS nanocomposite was prepared via free radical polymerization technique as shown in Scheme

1. In a typical reaction, 9.92 mmol of methyl methacrylate and 0.08 mmol of octavinyl-POSS (OVPOSS) in 5 mL

www.elsevier.com/locate/cclet

Chinese Chemical Letters 18 (2007) 960–962

* Corresponding author.

E-mail address: hongyaoxu@163.com (H.Y. Xu).

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

dried 1,4-dioxane were stirred for 8 h at 70 8C under a nitrogen atmosphere, using the AIBN initiator. The product was

then added dropwise into heated ethanol under vigorously agitation to dissolve the unreacted OVPOSS and methyl

methacrylate monomers and to precipitate the nanocomposite. The precipitated product was purified with 1,4-dioxane/

ethanol and characterized by 1H NMR and 29Si NMR spectroscopies. The thermogravimetric analysis was performed

in nitrogen flow at a ramp rate of 10 8C/min.

2. Results and discussion

Fig. 1 shows the 1H NMR spectra of OVPOSS, PMMA and PMMA–OVPOSS. For pure OVPOSS macromer, the

absorption band of vinyl protons is observed at d � 6.0 ppm as multiple peaks. For pure PMMA, the resonance band at

d � 3.6 ppm is attributed to the methyl proton connected to the ester group, and bands at d 1.4–2.0 and 0.7–1.1 ppm

belong to the resonance absorptions of methylene and the pendant methyl protons, respectively. The PMMA–

OVPOSS nanocomposite displays both absorptions at d 3.6, 1.4–2.0 and 0.7–1.1 ppm like PMMA and at d 6 ppm as

OVPOSS, indicating that the OVPOSS cages have been incorporated into the polymeric matrix.

Fig. 2 shows the 29Si NMR spectra of both pure OVPOSS macromer and PMMA–OVPOSS nanocomposite. For

pure octavinyl-POSS, there is only one resonance peak at d�79.3 ppm. For PMMA–OVPOSS, two resonance peaks at

d�79.2 and�65.3 ppm are attributed to the silicon atoms connected to the unreacted and the reacted vinyl groups on

the OVPOSS cages, respectively. The relative intensity of the resonance peaks at d�79.2 and�65.3 ppm implies that

most of the vinyl groups on OVPOSS have participated in the polymerization.

Fig. 3 displays the TGA thermograms of pure PMMA, PMMA/OVPOSS blend and PMMA–OVPOSS (0.85 mol%

of OVPOSS) nanocomposite. The PMMA homopolymer undergoes four-step degradations, and its Tdec (the

temperature of 5% weight loss) is 192 8C. The PMMA/OVPOSS blend shows three-step degradation with a Tdec of

177 8C. While the PMMA–OVPOSS nanocomposite only has one-step degradation and the Tdec is 256 8C, which is

64 8C higher than the mother polymer PMMA and 79 8C larger than PMMA/OVPOSS blend. It reveals that PMMA–

OVPOSS nanocomposite has better thermal stability than PMMA and PMMA/OVPOSS blend, implying that the

B.H. Yang et al. / Chinese Chemical Letters 18 (2007) 960–962 961

Scheme 1. Synthesis of PMMA–OVPOSS nanocomposite.

Fig. 1. 1H NMR spectra of PMMA–OVPOSS, PMMA, and OVPOSS.

incorporation of POSS into PMMA matrix by copolymerization is a good way to improve the thermal property of

PMMA.

Acknowledgments

This research was financially supported by the National Natural Science Foundation of China (Nos. 50472038 and

90606011), Program for New Century Excellent Talents in University (NCET-04-0588) and the Excellent Youth Fund

of Anhui Province (No. 04044060).

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B.H. Yang et al. / Chinese Chemical Letters 18 (2007) 960–962962

Fig. 2. 29Si NMR spectra of pure PMMA–OVPOSS and OVPOSS.

Fig. 3. TGA thermograms of pure PMMA, PMMA–OVPOSS copolymer and PMMA/OVPOSS blend.