Polyimide/nano-MgO composites without using any coupling agents or surface modifiers were prepared successfully by direct dispersing nano-MgO particles into the polyamic acid solution followed by spin coating and thermal imidization.The structures and properties of the composites were characterized by means of Fourier transform infrared spectroscopy (FTIR)

X-ray diffraction (XRD)

scanning electron microscopy (SEM)

Ultraviolet-visible spectroscopy (UV-Vis)

thermal gravimetric analyses (TGA) and nano-scratch test.The results showed that nano-MgO particles with average size of ca.20 nm were well dispersed in the polyimide matrix

and the compatibility between the organic and inorganic components was good.The as-prepared composites exhibited excellent optical transparency in the visible region and good UV-shielding properties in the near ultraviolet region.The UV-shielding properties of the composites increased with increasing amount of nano-MgO.It was found that the anti-scratch properties of the composites were enhanced substantially with the addition of nano-MgO.Under a scratching force of 100 N

the scratching depth dropped from 57.4 nm of pure PI to about 10 nm of PI/nano-MgO composites

and the width of the scratches also decreased significantly.Although the thermal stability of the composites was slightly inferior to pure PI

they still possessed fairly good thermal stability under the temperature of 300℃.