Development of polymerizable 2-(1-naphthyl)-5-phenyloxazole scintillators for ionizing radiation detection†
The synthesis, chemical characterization and optical properties of 2-(1-naphthyl)-4-vinyl-5-phenyloxazole (vNPO) and 2-(1-naphthyl)-4-allyl-5-phenyloxazole (allylNPO) monomers are reported. Starting with the organic fluor 2-(1-naphthyl)-5-phenyloxazole (αNPO), the vNPO and allylNPO monomers were synthesized using Stille coupling followed by purification. The final products were obtained with yields of ∼95% and ∼55% for vNPO and allylNPO. The absorption/emission spectra of αNPO, vNPO and allylNPO revealed that vNPO has the largest red-shifted in emission with an average wavelength of ∼420 nm, which is an advantage for increasing photomultiplier tube sensitivity without the need to add a wavelength shifter. Stable scintillating resin beads were prepared through copolymerization of the newly synthesized fluor monomers with styrene or 4-methylstyrene and divinylbenzene in the presence of toluene porogen. The resin beads were chemically stable and retained the ability to scintillate efficiently after energy deposition of beta particles from 99Tc. This result indicates efficient energy transfer occurs from the base polymer to the covalently attached fluors with subsequent fluorescence in the presence of ionizing radiation.