Synthesis and application of dimeric 1,3,5-triazine ethers as hole-blocking materials in electroluminescent devices

A series of low molecular weight dimeric 1,3,5-triazine ethers with high glass transition temperatures is synthesized from 2-(4-fluorophenyl)-4,6-diphenyl-1,3,5-triazine and various bisphenols. The thermal and electrochemical properties of these materials are examined using differential scanning calorimetry and cyclic voltammetry, respectively. The glass transition temperatures (T-g) are in the range of 106-144 degrees C, and all of them have similar thermal stability and show no weight loss up to 380 degrees C in thermogravimetric measurements. Some of these dimers form stable glasses which do not recrystallize on annealing at or above the T-g. Cyclic voltammetry studies reveal that these compounds undergo reversible reduction between -2.09 and -2.27 V vs ferrocene/ferrocenium as internal standard which correspond to LUMO values between -2.5 and -2.7 eV, respectively. The application of one of these dimeric ethers as a hole-blocking/electron-transport material in organic Light-emitting devices is demonstrated.