Phosphorescent oxygen sensors utilizing sulfur-nitrogen-phosphorus polymermatrixes: Synthesis, characterization, and evaluation of poly(thionylphosphazene)-b-poly(tetrahydrofuran) block copolymers

We examine the use of thionylphosphazene-based block copolymers as matrixes for oxygen sensor applications. Poly(aminothionylphosphazene)-b-poly(tetra hydrofuran) (PATP(y)-PTHFx) block copolymers were prepared via reaction of ring-opened poly(chlorothionylphosphazene) with THF and subsequently with e xcess It-butylamine (to form PBATP(y)-PTHFx) or methylamine (to form PMATP( y)-PTHFx), The block copolymers were characterized by NMR, gel permeation c hromatography, and differential scanning calorimetry. Films of PBATP(y)-PTH Fx block copolymers containing platinum octaethylporphyrin or [Ru(dpp)(3)]C l-2 (dpp = 4,7-diphenyl-1,10-phenanthroline) as the oxygen-sensitive chromo phore were prepared, and time-scan experiments were carried out to determin e the diffusion coefficients, D-O2, and solubilities, S-O2, of oxygen there in. Despite microphase separation, the data fit well to a simple Fick's law description of oxygen diffusion and gave D-O2 values smaller than that for the n-butylamino-substituted PBATP(635), For films freshly annealed above the melting point of PTHFx, the D-O2 values were 35-50% (dye-dependent) lar ger than after aging 3 days at room temperature. Films with [Ru(dpp)(3)]Cl- 2 as the dye were evaluated as media for phosphorescent pressure-sensing. T he dye-containing polymer films exhibit linear Stern-Volmer-like plots, eve n at high dye concentrations, as well as good photostability, and significa ntly higher sensitivity to oxygen quenching than simple mixtures of the ana logous homopolymers.