Surface Modification via Chain End Segregation in Polymer Blends

We have explored the use of chain end segregation as a means of controlling the properties of a polymer surface. Thin film blends of homopolystyrene (PS) and PS synthesized with low-energy oligotetrafluoroethylene chain ends (PS-TFE) were studied using neutron reflectivity. The fraction of PS-TFE that localizes near the surface was found to increase as a function of its concentration in the blend. Contact angle measurements indicate corresponding reductions in the surface tension due to the surface localization of the TFE chain ends. For a 10% blend of 6000 mol wt PS-TFE in 3 × 105 mol wt PS, the surface coverage of fluorocarbon ends was found to be >20%. A free energy model of the blends gives good qualitative agreement with the experimental results.