High porosity scintillating polymer resins for ionizing radiation sensor applications

Due to their high sorption capacity, nanoporous polymer resins can be used as an active material for ionizing radiation sensor applications. This contribution reports on the molecular design and synthesis of scintillating styrene-based resins with controlled bead size, porosity and surface functionality. In a working sensor device, the adsorption of radioactive analyte species on the resin can be monitored via incorporation of specially designed fluor molecules to convert ionizing radiation (specifically, α-particles and β-particles) into light. Porous polystyrene (PS) and poly(4-methylstyrene) resins of various compositions and structure were synthesized via suspension polymerization technique. 1,4-Bis(4-methyl-5- phenyl-oxazol-2-yl)benzene (DM-POPOP) was incorporated into the resin by adding it to the dispersed phase. Polymerization conditions were adjusted to achieve a desirable range of polymer beads size and porosity (pore size distribution, specific surface area). The porosity of the resin beads could be controlled by the type and concentration of the porogen, as well as by the degree of PS matrix crosslinking with divinylbenzene. Three different porogens (toluene, n-heptane or span-80 nonionic surfactant) were used to achieve a broad variation of the nanopore size distribution within the same matrix. The structure, porosity and optical fluorescence properties of the synthesized PS beads were analyzed with nitrogen adsorption porosimetry, optical/UV confocal, scanning electron and helium ion microscopy, and fluorescence spectroscopy. A broad variation of the pore size distribution, specific surface area and optical properties within the same system were demonstrated. Findings from this study can be used for the development of more efficient environmental sensors to monitor contamination of ground water with trace amounts of radioactive materials.