Colloidal aqueous dispersions of poly(n-butyl acrylate) (PBA)-silica (SiO2) nanocomposite particles were synthesized through free radical polymerization in the presence of SiO2 nanoparticles and poly(N-vinyl pyrrolidone) colloidal stabilizer using a cationic radical initiator. The nanocomposite particles were stable colloids with a reasonably narrow size distribution and a SiO2 content of 40%. Morphology of the nanocomposite particles was confirmed to involve a PBA-core/SiO2 nanoparticle-shell using electron microscopies. Pressure-sensitive adhesive (PSA) films were prepared from blends of the nanocomposite particles and PBA homopolymer particles at various weight ratios. Probe tack tests at the standard probe rate, which is close to the actual peeling speed for PSAs, confirmed that maximum stress of tack adhesion improved 2.36 times and adhesion energy improved 1.39 times upon addition of nanocomposite particles compared to that of PBA homopolymer film. The nano-scale mechanical deformation and energy dissipation ability of the 'soft-hard' nanocomposite particles was expected to increase adhesion energy. (C) 2015 Elsevier Ltd. All rights reserved.