Effect of Solvent and Solute Structure on Scintillator Pulse Heights. I. Correlation of Pulse Heights for Ring Substituted Styrene Plastic Scintillators with Hammett Substituent Constants

Abstract

A group of different ring substituted styrene plastic scintillators were prepared with a constant concentration of p-terphenyl as the fluor and POPOP as the waveshifter. The effect of this variation in the structure of the polymer phase on pulse-height response to β and γ radiation was determined. It was found that correlations exist between the relative pulse height and the Hammett (δ) and Taft (δI) substituent constants for the substituted polystyrenes. Pulse heights increase with an increase in the negative value of the substituent constant, i.e., with an increase in the electron-donating power of the ring substituent on the polystyrene. It was found that markedly lower relative pulse heights were obtained for a series of styrene plastics in which the α-hydrogen in the backbone chain was substituted by a methyl group. This suggests that an α-hydrogen in the backbone chain is required for an efficient plastic solvent.