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Silica nanotubes (SNTs) were synthesized via sol-gel method using ammonium tartrate as template, and then spherical nano-silica (SiO 2 ) and SNTs which have different geometric morphology were introduced into polymer matrix to obtain polymethyl methacrylate (PMMA)/SiO 2 and PMMA/SNTs microspheres via in situ suspension polymerization, respectively. The morphology of synthesized SNTs and microspheres were observed by scanning electron microscope (SEM), while the structure of SiO 2 and SNTs, as well as the interaction between PMMA and SiO 2 or SNTs were characterized by Fourier transform infrared spectroscopy. The dispersion of SiO 2 in the PMMA/SiO 2 nanocomposites was observed by transmission electron microscopy (TEM). The molecular weight of the extracted PMMA was measured by gel permeation chromatograph. Finally, the mechanical properties were studied in detail and the tensile fracture surface was studied by SEM. The result indicated that, SNTs with uniform size and high aspect ratio were prepared successfully, and the mechanical properties of PMMA/SNTs nanocomposites were improved greatly due to the introducing of SNTs. However, the mechanical properties of the PMMA/SiO 2 nanocomposites decreased overall. Due to the special tubular structure of SNTs, it is much easier for them to be dispersed in polymer matrix compared with spherical SiO 2 . This work reveals the potential application of SNTs in polymer-based nanocomposites.

In this work, methyl methacrylate (MMA) copolymerized with cationic monomer 2-(methacryloyloxy)ethyltrimethylammonium chloride (MTC) via in situ suspension copolymerization, meanwhile, negatively charged carboxylic multi-walled carbon nanotubes (MWCNTs) were adsorbed through electrostatic interactions during copolymerization process to fabricate nanocomposites. The chemical structure of copolymer was analyzed by 1 H nuclear magnetic resonance ( 1 H-NMR). The interfacial adhesion between MWCNTs and polymer matrix was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The morphologies of synthesized microspheres were observed by SEM. Finally, the mechanical properties of nanocomposites were investigated in detail. The results suggest that: the nanocomposites have been successfully synthesized by in situ suspension copolymerization; both the dispersion of MWCNTs and interfacial adhesion between MWCNTs and matrix were improved; and the mechanical properties of nanocomposites were dramatically reinforced. The nanocomposites were prepared in one step without additional treatments of MWCNTs or copolymer matrix, which makes the method relatively efficient.

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