Effects of different matrixes on the dosimetric response of alpha-terthiophene films from the kgy to mgy range

Films of polymethylmethacrylate (PMMA) and polystyrene (PS) containing alpha-terthiophene (3T) undergo a radiochromic effect when exposed to electrons and gamma rays. The films turn either red-green or red, due to the formation of oligomeric radical cations. In both matrixes, absorbance at 465 nm grows linearly with dose when alpha-terthiophene concentration reaches 12%. Explored range goes up to ~ 2 x 10^6 Gy, with dose rates spanning over three orders of magnitude. Concerning their application as dosimeters, a higher sensitivity characterises the 3T-PMMA moiety, suggesting its suitability from the kGy range up to 1 MGy. Above this value films become fragile. 3T-Polystyrene films are less sensitive, but more radiation resistant. Therefore they better suit the medium-to-high dose dosimetry range. Dose rate influences the response sensitivity in a complex way, however above 80 and up to 3.6 x 10^4 Gy/min an approximate linearity exists between log(dose rate) and sensitivity, as in the analogous cellulose triacetate system.