Method for measuring oxygen diffusion coefficients of polymer films by luminescence quenching

To ascertain the relationship between the physical properties of polymer supports and the observed response of luminescence-based oxygen sensors, a quenching-based method was developed to measure oxygen diffusion in polymers. The method offers advantages over existing quenching-based techniques since it allows a simple correction for films of high optical density, and the computations do not assume uniform oxygen concentration throughout the film. Diffusion coefficients (D) were measured for a series of sensors with [Ru(Ph2phen)3]Cl2 (Ph2phen = 4,7-diphenyl-1,10-phenanthroline) asthe luminophore and polystyrene, poly(trimethylsilylmethyl methacrylate), poly(butyl methacrylate), poly(trimethylsilylmethyl methacrylate-co-butyl methacrylate), or poly(trimethylsilylmethyl methacrylate-co-1H, 1H-heptafluorobutyl methacrylate) as the support. The solvent from which the films were cast was varied, and filler materials such as hydrophobic, amorphous silica or tributyl phosphate plasticizer were added. Results are interpreted by a domain model in which the local environment of the sensor, rather than the bulk properties of the polymer, is the most critical parameter in sensor design.