Use of RuO4 in studies of polymer blends by scanning electron microscopy

Flat samples of blends of PP and SEBS were contrasted with ruthenium tetroxide and studied in a scanning electron microscope provided with a detector for back-scattered electrons. The images showed the SEBS phase as bright areas with dark dots and the PP phase as dark. The dots in the bright SEBS areas corresponded to the unstained EB-domains of the triblock SEBS polymer. The technique used provided BSE images of high resolution. This is a consequence of the intrinsic electrical conductivity conferred to the sample surface by the ruthenium species deposited there during staining. Treatment with ruthenium tetroxide vapor conferred electrical conductivity to the stained areas, which explains the high resolution obtained with the present technique.