Structures of collapsed polysiloxane monolayers investigated by scanning force microscopy

Surface pressure-area isotherms of monolayers of cyclolinear polysiloxanes on water exhibit several plateaus that have been associated with the formation of multilayers. This stepwise collapse has been studied in one of these polymers by scanning force microscopy under topographic, frictional, and electric force modes. Topographic images show that the growth of the second layer begins with the nucleation of three-dimensional islands, which then appear to spread in the form of ribbons 0.5 mu m wide and 7.5 Angstrom high. The number of ribbons increases as the extent of the second layer increases, but the width of the ribbons remains constant. Subsequent layers do not exhibit this morphology.