Imaging of hydrogen atoms and stacks of phenyl groups on the surface of polystyrene microparticles by scanning tunneling microscopy

Polystyrene microparticles prepared by microemulsion free-radical polymerization have been investigated using a scanning tunneling microscope. It has been found that the polymer chains are extended without entanglement in some regions of the polymer surface. The hydrogen atoms on the upward rim of the phenyl groups can be distinguished by atom-resolved imaging. The phenyl groups in the same chain can stack up as a parallel-displaced structure, similar to that predicted for benzene dimers. The existence of the orderly stacked polymer chains and phenyl groups may be due to the fact that the polymerization is constrained in a very limited space.