The polymer APFO(3) was prepared with different molecular weights to study how the infiltration into nanoporous TiO2 films of different thickness depends on the size of the polymer. Also two different sizes of TiO2 nanoparticles were investigated to understand the effect of different pore size. It was observed that the lowest molecular weight polymer dissolved in chlorobenzene could infiltrate the nanoporous TiO2 network up to several micrometer thick films. It was concluded that efficient polymer infiltration into thick nanoporous layers was possible for the polymers with an estimated average chain length smaller than the diameter of the nanoparticles. (C) 2010 Elsevier B.V. All rights reserved.