Phase separation in polyfluorene blends investigated with complementary scanning probe microscopies

Abstract Fluorescence scanning near field optical microscopy and tapping mode atomic force microscopy have been used to investigate a blend of the polyfluorene based polymers F8BT and PFB. Images acquired from the film, which contains 10 wt-% F8BT, show the presence of micrometre size regions protruding from the surface of the film, unambiguously identified from their fluorescence as F8BT rich. However, comparatively strong and locally varying fluorescence from F8BT is also detected in the PFB rich phase, which is topographically flat apart from small ~30 nm diameter protrusions identified as PFB from their presence in a pure PFB film. It is demonstrated that the combined application of scanning near field optical microscopy and atomic force microscopy to the study of such blends is able to assist our understanding of the nature of phase separation and photoinduced charge transfer.