Self-assembled polyelectrolyte thin films: Film morphology and ionic strength

We present the results of an atomic force microscopy study of the self-assembly of poly(p-xylylene tetrahydrothiophenium) (precursor PPV) and poly(styrene sulphonate) (PSS) on functionalised fused quartz substrates. The morphology of these polyelectrolyte films depends on the ionic strength (I) of the assembly solutions. The film surface can be tuned from a non-scattering state to a highly-scattering one as the film roughness increases with I. The results suggest that polymer chain conformations vary significantly with the ionic environment present during self-assembly and this should be taken into account when interpreting photophysical results of these systems.