Exploring the effect of porphyrin chemical structure on the performance of polymer-based Pressure-Sensitive Paints

Abstract

Pressure sensitive paints (PSPs) are a powerful optical oxygen sensor technique for measuring the surface pressure distribution upon an aircraft model in wind tunnel testing. Traditional PSPs have relied heavily on platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorphenyl)-porphyrin due to its reasonable quantum yield of emission, high pressure sensitivity, resistance to photo oxidation, and commercial availability. This work investigates the effect of luminophore chemical structure on PSP performance by altering the degree, substitution pattern, and nature of halogen atom on the phenyl groups of ten different Pt(II) tetraphenyl porphyrins. From this initial screening it was found that platinum(II)-5,10,15,20-tetrakis-(3,5-bis(trifluoromethyl)phenyl)-porphyrin polymer PSPs had a substantially lower temperature sensitivity and a slightly higher pressure sensitivity. Using this new luminophore a Fluoro/Isopropyl/Butyl (FIB) polymer based PSP formulation was optimised whereby it was found that 3.2% w/v of FIB polymer and 800 μM concentration of platinum(II)-5,10,15,20-tetrakis-(3,5-bis(trifluoromethyl)phenyl)-porphyrin gave a low temperature sensitivity at 100 kPa for a single component polymer based PSP of 0.22%/K and a relatively high pressure sensitivity at 293 K of 0.846, exceeding current commercial PSP performance.