Effect of reactive species on surface crosslinking of plasma-treated polymers investigated by surface force microscopy

Polymer surface modification by ions, uncharged particles, and photons of inductively coupled Ar plasma was investigated with a surface force microscope. Optical windows consisting of crystals with different cutoff wavelengths and a metal shield were used to deconvolute the effects of the various plasma species on the modification of the surface nanomechanical properties of polyethylene. The extent of surface crosslinking was related to the frictional energy dissipated during nanoscratching. It is shown that surface crosslinking is primarily due to the simultaneous effects of uncharged particles and vacuum ultraviolet photons, while the ion bombardment effect is secondary. (c) 2006 American Institute of Physics.