Allison Lim


Materials Chemist

Improving Material Properties of Plastic Scintillators


Problem:
Plastic scintillators for can discriminate between neutrons and gamma rays. However, the high concentration of  small molecule dopant required leads to undesirable plasticizing effects such as softening, low glass transition temperature, and dopant aggregation and leaching.

Hypothesis:
Cross-linking and polymerizable dopants may mitigate plasticizing effects by increasing the rigidity and covalently bonding the dopant with the polymer matrix.

Summary of Results:
  • Identified a commercial and synthesized cross-linker  structure-property relationships developed in collaboration with physicists and nuclear engineers
  • Fabricated cross-linked samples with 10x higher Shore-D hardness and equivalent radiation detection capabilities.
  • Synthesized novel polymerizable dopants and co-polymerized with vinyl toluene to eliminate dopant leaching. Two synthetic dopants retained radiation detection capabilities.
Relationship between concentration of cross-linker (BPA-DM) and FoM, a metric of radiation detection capabilities (top). Constant FoM implies radiation detection capabilities are retained. (Bottom) Relationship between hardness and cross-linking. Increasing concentration of cross-linker increases the hardness.

Publications


Methacrylate-Functionalized 2,5-Diphenyloxazole for Use as Fluorescent Monomers in Plastic Scintillators


Allison Lim, Griselda Hernandez, Joseph Latta, Henok A. Yemam, Wasana Senevirathna, Uwe Greife, Alan Sellinger


ACS Applied Polymer Materials, vol. 1(6), 2019 Mar 21, pp. 1420-1429


Methacrylate based cross-linkers for improved thermomechanical properties and retention of radiation detection response in plastic scintillators


Adam Mahl, Allison Lim, Joseph Latta, Henok A. Yemam, Uwe Greife, Alan Sellinger


Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2018 Jan 28, pp. 113-118