| Abstract: | A novel method for the measurement of oxygen permeability through polymer membranes is described. It is based on monitoring the sensitized photo-oxygenation of a singlet oxygen acceptor in a detector layer sandwiched between a support and the polymer layer under test. The detector layer contains a sensitizer which on irradiation produces singlet excited oxygen from the ground-state oxygen available. The singlet oxygen reacts with an oxygen acceptor, the disappearance of which can be followed by spectrophotometry. In the photostationary state, changes in the acceptor absorbance are directly related to the overall flux of oxygen through the polymer membrane. It can be shown that the permeation coefficient P of oxygen is proportional to the rate of change in acceptor absorbance and to the inverse of the oxygen concentration in the surrounding atmosphere. It is given by the expression  where ? is the molar extinction coefficient, ΔC is the difference in the oxygen concentration on the two sides of the polymer membrane, ΔD is the change in optical density during the time interval Δt, and l is the thickness of the polymer membrane. The method is comparatively simple and rapid and provides data for polymers that are difficult to study by more conventional methods. Oxygen permeabilities were measured for a group of water-soluble polymers. |
