Using the amphiphilic alternating copolymer poly(styrene-alt-maleic anhydride), the hydrophobic salt PtCl2, is reduced into platinum nanoparticles that are less than 3 nm in an aqueous biocompatible environment. The nanoparticles are characterized by transmission electron microscopy and X-ray diffraction. The formation of unsupported nanoparticles embedded in the polymer nanotemplate take advantage of the confinement effect in reactions due to the dynamic formation of the poly(styrene-alt-maleic anhydride) nanotube. This enhanced catalytic effect is demonstrated with the polymerization of pyrrole. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.