The light-induced self-assembly of gold nanoparticles was studied systematically. A methacrylate type monomer with an azobenzene sidechain was polymerized in a reversible addition-fragmentation chain transfer (RAFT) polymerization. The resulting light responsive polymer was grafted to gold nanoparticles via the RAFT group. UV-light induced trans to cis isomerization of the azobenzene moieties triggers the aggregation of the polymer-gold hybrid particles in toluene dispersion. The thermally induced cis to trans relaxation was found to be significantly slower than for small molecules at gold surfaces. The self-assembly was followed by dynamic light scattering (DLS), UV/vis spectroscopy and transmission electron microscopy (TEM). The density of primary gold particles within the self-assembled aggregates can be tuned by varying the molar mass of the grafted polymer. (C) 2016 Elsevier Ltd. All rights reserved.