4 4 diaminodiphenyl ether

Potassium carbonate, sodium hydroxide, methanol, and acetone were purchased from Sinopharm Chemical Reagent Co. (Shanghai, China). 4,6-Diamino-2-mercapto-pyrimidine was purchased from Aladdin (Shanghai, China). 1,6-Dibromohexane and 4-cyano-4′-hydroxybiphenyl were obtained from J&K Reagent Co. (Beijing, China). 4,4′-Diaminodiphenyl ether (ODA) was purchased from Alfa Aesar (Ward Hill, MA, USA) and purified by recrystallization from ethanol. 4,4′-Oxydiphthalic anhydride (ODPA; >99%, Suzhou Yacoo Chemical Reagent Corporation, Jiangsu, China) was purified by recrystallization from acetic anhydride and dried under vacuum prior to use. N,N′-Dimethylformamide (DMF) and N,N′-dimethylacetamide (DMAc) were distilled under reduced pressure after stirring over calcium hydride for 24 h and stored over 4 Å molecular sieves before use. A nematic LC of 4′-pentyl-4-cyanobiphenyl (5CB) (n_o = 1.533, n_e = 1.716) was purchased from Adamas (Shanghai, China).