Chemical surface modification of aluminum oxide (AO) nanoparticles with graft copolymer of AO and poly (isobutyl vinyl ether) (PIBVE) (AO-graft-PIBVE) was carried out by ball milling of AO nanoparticles with IBVE in vacuum at low temperature. The AO-graft-PIBVE was evidenced by FT-IR and 1H NMR spectra. The surface modified AO nanoparticles with mono-dispersed particle diameter exhibited structural blue color which was evidenced by photograph, optical spectroscopy (UV-Vis-NIR) and SEM image. The key atoms for the mechanochemical reactions were assigned by the net charge and the distribution of the HOMO and/or LUMO at each atom estimated by molecular orbital calculations. The reaction scheme is proposed; naked Al cations of AO (AO-Al+) were produced by ionic scission of aluminum-oxygen bond by ball milling and trapped at the surface of AO nanoparticles. The AO-Al+ reacted with IBVE, formed a novel bond between the Al-atom of AO-AP and the C-atom of IBVE, and resulted in AO-Al-IBVE+. The AO-AI-IBVE+ sequentially reacted to the C-atom of IBVE, and finally resulted in AO-graft-PIBVE. The PIBVE homopolymer was simultaneously produced by the ball milling of AO with IBVE in vacuum at low temperature. The key atoms for the reactions were assigned by the molecular orbital calculations. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.