"Log-Rolling" Alignment in Friction-Transferred Light-Emitting Conjugated Polymer Thin Films

Thin films of a water soluble poly(phenylenevinylene) (PPV) derivative with sulfonate containing side chains (DPS PPV) were formed on silica substrates by a solvent free friction transfer technique The films were highly aggregated producing "rods of polymer aligned perpendicular to the drawing direction This log rolling is in contrast with the reported behavior of most comparable polymers which tend to align along the drawing direction The photophysical behavior of the friction transferred film is also different compared with other film formation techniques of the same polymer Comparison of the steady state and time-resolved emission characteristics of these films with films coated by the conventional drop-casting method reveals that short lived fluorescence components are dominant in the highly aggregated friction transferred polymer films compared to less aggregated drop-cast films in which long lived emission species are favored This highlights the importance of the film formation processes on the properties of the film