A post-modification process based in the swelling of polymeric nanoparticles with a low boiling point alkane (n-pentane) to decrease the viscosity of the polymer phase and promote a controlled coalescence succeeded to change particle morphology and size of preformed polymer latexes. The swelling procedure was performed at 120 degrees C followed by pressure release at temperatures lower than the T-g of the pure polymer and higher than the boiling point of n-pentane to promote the complete recovery of the alkane. Polystyrene latexes with different particle sizes and molar masses were prepared by emulsion and miniemulsion polymerizations. The post-modification of the latexes was evaluated at different n-pentane contents and temperature of pressure release. Results showed that the emulsion polymerization latexes with smaller particle size (approximate to 60 nm) underwent controlled coalescence resulting in stable latexes of spherical particles with diameter in the range of 600-1000 nm, while latexes with larger particles (above 200 nm) showed little sign of coalescence under the same swelling and pressure release conditions. The presence of a medium molar mass alkane (hexadecane) in the polymeric particles obtained by miniemulsion polymerization resulted in nanocapsules morphology probably due to polymer-alkane phase segregation during the swelling procedure. (C) 2015 Elsevier B.V. All rights reserved.