Nano-beads of controlled size of a conjugated polymer, polyphenylacetylene (PPA), were prepared for the first time by using a catalytic emulsion polymerisation technique. Reaction conditions, such as concentration of monomer, co-solvent, and reaction time, were varied in order to study the feasibility of tuning particle size and their self-assembling properties. Besides routine chemical analysis, the new prepared materials were characterised by Scanning Electron Microscopy (SEM) in order to determine the diameters of the beads and their size dispersion. The beads have regular round shape, with diameters ranging from 300 to 1000 nm depending on the reaction conditions, and 14 when a low degree of polydispersion is achieved, a short range regular array occur. (C) 2003 Elsevier B.V. All rights reserved.