Synthesis of new ferrocene containing diamines and their use in epoxy resins

Treatment of 4,4-bis(ferrocenyl)heptane-1,7-diol (1) with benzenesulfonyl chloride afforded after workup and crystallization, 4,4-bis(ferrocenyl)-heptane-1,7-bis(benzenesulfonate) (2) in 67% isolated yield. Compound 2 was reacted with sodium 3-aminophenoxide or sodium 4-aminophenoxide in DMF to afford 1,7-bis(3-aminophenoxy)-4,4-bis(ferrocenyl)heptane (3a) (80%) and 1,7-bis(4-aminophenoxy)-4,4-bis(ferrocenyl)heptane (3b) (88%), respectively. Compounds 3a and 3b were copolymerized with methylenedianiline (MDA) and Epon® Resin 828 to afford fully cured epoxy resins. We found 3b to cure faster than 3a by DSC analysis. Samples of the cured resins with 20 mol% of 3a and without ferrocene monomer were prepared with engineered defects (polypropylene letters 3 mm thick) and subjected to X-ray analysis. The samples containing ferrocene show good contrast of the defects under mild X-ray imaging conditions; whereas, non-ferrocene containing samples did not allow detection of the engineered defects.