XPS analysis of NH3 plasma‐treated polystyrene films utilizing gas phase chemical modification

Gas phase chemical modification (GCM) is found to be more preferable as a pretreatment for the XPS surface analysis of polymer materials than the conventional liquid phase treatment because it can circumvent problems such as solvent contamination and swelling. We have tried the quantification of the surface composition successfully by estimating the yield of the reaction from model samples. GCM was then applied to correlate the surface composition of NH3 plasma‐treated polystyrene films with their cell‐affinity. The amount of primary‐amine and that of carboxylic acid were directly determined by GCM. Although the amount of primary‐amine, 15–20% of total nitrogen, did not depend on the treatment intensity, the total amine content for the treated samples increased with the plasma treatment intensity. The quantity of carboxylic acid generated was found to be very small. All treated samples had better cell‐affinity than the control. The sample N2 (of medium treatment) showed the best cell‐affinity. The most strongly treated sample N3, with larger amine content than N2, showed worse cell‐affinity because of the interference by the sputtered SiO2 on the surface.