Determination of graft density of substrate-supported polymer films

Determining the graft density of polymers adsorbed on a substrate from neutron scattering-length density profile can be challenging. A scheme based on integrating a select region of the profile is proposed and applied to results obtained from a recent neutron reflectometry experiment that investigated the physical properties of polyethylene oxide (PEO) chemisorbed onto a gold-coated Si substrate. Reflectivity measurements were performed with the PEO exposed to a H2O/D2O mixture contrast matched to the underlying gold. The graft density obtained by the integration technique is 60% higher than the value determined using scaling relations.