Phosphorescent Oxygen Sensors Utilizing Sulfur−Nitrogen−Phosphorus Polymer Matrixes:  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(tetrahydrofuran) (PATP y −PTHF x ) block copolymers were prepared via reaction of ring-opened poly(chlorothionylphosphazene) with THF and subsequently with excess n-butylamine (to form PBATP y −PTHF x ) or methylamine (to form PMATP y −PTHF x ). The block copolymers were characterized by NMR, gel permeation chromatography, and differential scanning calorimetry. Films of PBATP y −PTHF x block copolymers containing platinum octaethylporphyrin or [Ru(dpp)3]Cl2 (dpp = 4,7-diphenyl-1,10-phenanthroline) as the oxygen-sensitive chromophore were prepared, and time-scan experiments were carried out to determine the diffusion coefficients, D O 2 , and solubilities, S O 2 , of oxygen therein. Despite microphase separation, the data fit well to a simple Fick's law description of oxygen diffusion and gave D O 2 values smaller than that for the n-butylamino-substituted PBATP635. For films freshly annealed above the melting point of PTHF x , the D O 2 values were 35−50% (dye-dependent) larger than after aging 3 days at room temperature. Films with [Ru(dpp)3]Cl2 as the dye were evaluated as media for phosphorescent pressure-sensing. The dye-containing polymer films exhibit linear Stern−Volmer-like plots, even at high dye concentrations, as well as good photostability, and significantly higher sensitivity to oxygen quenching than simple mixtures of the analogous homopolymers.