Radiochemical studies of the leaching of primary scintillator molecules from within sol-gel glasses

Tritium labelled 2,5-diphenyloxazole ([H-3]-PPO, 1) and 4-hydroxymethyl-2,5-diphenyloxazole ([H-3]-4-HOCH2-PPO, 2) have been prepared using a one-step metal catalysed isotope exchange procedure. Compound 1 was then encapsulated into a sol-gel glass via the polymerisation of tetraethyl orthosilicate (TEOS). Compound 2 was first reacted with 3-isocyanatopropyltriethoxysilane (3-ICPS) to form a functionalised silicon alkoxide precursor which has a urethane linkage ([H-3]-urethane 4), and subsequently copolymerised with TEOS to form covalently bonded sol-gel glasses. The performance of the two glasses was differentiated on the basis of radioactivity leaching tests. In the case of the covalently bound version virtually no leaching occurred, thereby making it an attractive candidate for further applications.