Polyimides containing oxyethylene units

Four aromatic dinitro compounds containing oxyethylene units 1,2‐bis(4‐nitrophenoxy)ethane, bis(2)‐(4‐nitrophenoxy)ethyl ether, 1,2‐bis(2)‐(4‐nitrophenoxy)ethoxy)ethane, and bis(2‐(2‐(4‐nitrophenoxy)ethoxy)ethyl) ether were prepared by an aromatic nucleophilic substitution reaction that involved 1‐fluoro‐4‐nitrobenzene and the appropriate oxyethylene glycol. Each of the dinitro compounds could be reduced chemically or catalytically to produce the diamines 1,2‐bis(4‐aminophenoxy)ethane, bis(2‐(4‐amino‐phenoxy)ethyl ether, 1,2‐bis(2‐(4‐aminophenoxy)ethoxy)ethane, and bis(2‐(2‐(4‐aminophenoxy)ethoxy)ethyl) ether. Polymerization of the diamines was carried out in m‐cresol with toluene as an azeotroping agent. Polymides derived from 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl)ethylidene]bis‐1,3‐isobenzofuradione exhibited good solubility in chlorinated solvents, glass transition temperatures as low as 140°C, as evidenced by viscous flow, and good thermal stability; a 5% weight loss generally occured at greater than 450°C. Isothermal aging studies conducted at 600°F(315°C) for 200 h indicated that weight loss is directly related to oxyalkylene chain length–10% for the shortest and 50% for the longest chain.