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 paralleldisplaced
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.