Radio frequency plasma polymers of n-butyl methacrylate and their controlled drug release characteristics: I. Effect of the oxygen gas

The effect of oxygen gas on the chemical structure, surface property and controlled drug release characteristics of radio frequency (RF) plasma poly-n-butyl methacrylate (PPBMA) thin films was investigated. The ATR–FTIR and XPS spectra of the resultant PPBMA films showed relatively higher concentration of C–H, C–C and CC groups, but less intense peaks of CO and C–O functionalities, which imply that the oxygen gas had no significant influence on the chemical structure of the plasma films. Results of the SEM experiment revealed that a dome-like structure was observed in the case of deposition without oxygen, but in the case of deposition with oxygen, a smooth and dense surface was produced. Moreover, the hydrophilicity of PPBMA obtained from the deposition with oxygen was higher than that without oxygen. Drug release from PPBMA deposition coating without oxygen had biphasic patterns, a fast release followed by a slow release, but the one with oxygen exhibited a slow Higuchi release.