Improving Wettability of PoIyMethylMetiiAcrylate by Ar+ ion Irradiation in Oxygen Environment

Ion irradiation has been carried out to improve wettability of PMMA to water. The polymer was irradiated by argon and oxygen ions, and amount of ions was changed from 1014 ArVcm2 to 5xl016Ar+/cm2. Ions energies were varied from 0.5 keV to 1.5 keV, and oxygen gas was flowed from 0 seem to 6 scan near the polymer surface during ion irradiation. Wetting angle was reduced from 68 degree to 49 degree with increasing Ar+ ion irradiation, to 43 degree with Ch+ ion irradiation, and dropped to 8 degree with Ar+ ion irradiation with flowing 4 seem oxygen gas near the polymer surface. Recovery of wettability in dry air condition, and maintenance of it in dilute HC1 solution were explained in a view of formation of hydrophilic groups due to a reaction between irradiated polymer chain by energetic ion irradiation and flowing oxygen near the surface. Reactions among polymer matrix, energetic ions and oxygen gas to form hydrophilic group by energetic ions were discussed in terms of a two-step reaction, in which the first step is the creation of an unstable polymer chain by the ion irradiation and the second step is a reaction between the radicals and the oxygen gas.