Polymerizable Oxygen Probe Derived from Platinum-Based Porphyrins for Oxygen Sensing and Pressure-Sensitive Paints

In this work, a polymerizable oxygen probe (PtTFPP-1MA) derived from platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin (PtTFPP) was synthesized and characterized. The probe PtTFPP-1MA with a methacrylate unit can be copolymerized with other monomers; herein, we used t-butyl styrene (tBs) as a representative monomer for the oxygen sensor and pressure-sensitive paint (PSP). Three copolymers of poly(tBs-co-(PtTFPP-1MA)) (P1a–c) with different PtTFPP-1MA contents were synthesized. Results showed that the oxygen-sensing ability of these polymers exhibited similar oxygen sensitivity, indicating that the compositions of the probe concentrations in our chosen ranges did not have significant influences on sensing. To determine the properties' difference of probe between the physical doping approach with the chemical copolymerization method in the polymer matrix, poly(tBs) (P2) without PtTFPP-1MA were prepared. Results showed that the polymers (P1a–c) prepared by the chemical copolymerization method exhibited better performance in oxygen- and pressure-sensing tests. In order to investigate whether steric hindrance of the bulky t-butyl group has a significant effect on sensing, poly(St-co-(PtTFPP-1MA)) (P3) using polystyrene with the t-butyl moiety as the matrix was synthesized for comparison. Results confirmed that P1a with the bulky t-butyl group possesses much better sensing performance than P3. P1a's pressure sensitivity (0.75%/kPa) at 20 °C is among the highest values in reported PSPs, and its temperature sensitivity (−0.63%/°C) at 100 kPa is among the lowest in reported PSPs. It is expected that the polymerizable oxygen probe PtTFPP-1MA could be widely used in oxygen sensors and PSPs.