Reduction of radiation-induced conductivity in poly(ethylene terephthalate): Effect of dopant structure

This paper focuses on developing radiation tolerant polymeric films by incorporating small molecule dopants into the material formulation. The radiation tolerance is imparted to the polymer by dopants capturing the mobile electrons generated upon radiation exposure. A wide range of conjugated small molecules was utilized for the reduction of radiation-induced conductivity (RIC) in semi-crystalline poly(ethylene terephthalate). Using these results, the process of electron and hole trapping by π-conjugated molecules may be generalized to many organic systems. All conjugated ring cores examined, when substituted with an appropriate electron-withdrawing species, led to excellent RIC reduction. The nitro group is the strongest electron-withdrawing substituent, and therefore leads to the lowest RIC, but other substituents also reduce RIC, and the interactions may be quantified by the Hammett parameter. It was also found that the dopant must be present in a certain range of concentrations, between 10 and 200 mol/m3 (6 × 1018 and 1 × 1020 molecules/cm3), for proper trapping of the photo-induced electron-hole pairs. This understanding of the interactions between conjugated dopants, photons, and electrons will benefit other applications, such as controlled conductivity in coatings and organic electronics.