The outermost surface of a nanodiamond was modified with long-chain phosphonic acids. The thermal desorption of the modified chain was suppressed until 350 A degrees C. Nanohybrids of the phosphonic acid-modified nanodiamonds were formed by melt-compounding them with transparent polymers with high melting points over 230 A degrees C. The transparency of the nanohybrids containing the nanodiamonds was maintained and the size of the aggregated nanoparticles on the surface was found to be in the range of 40-70 nm. The melting temperature of the nanohybrid increased compared to that of the matrix polymer, and the D (200) crystallite size also improved. In addition, mechanical properties improved, and thermal degradation temperatures also increased; this is attributed to the good dispersion of the nanodiamonds in the polymer matrix. Furthermore, the nanohybrid exhibited the image projection ability derived from nanodiamonds with high refractive index dispersed in the matrix. Darkening due to carbonization was observed in the nanohybrid consisting of crystalline-fluorinated polymers, but it was overcome by complexing the modified nanodiamond with a fluorinated long-chain phosphonic acid. The desorbed modified chains were assumed to get incorporated into the fluoropolymer with a high molten viscosity and cause carbonization, and it seems that the miscibility of the fluorinated-modified chain resolved this issue. [GRAPHICS] .