Synthesis and properties of novel polyimides from 3‐(4‐aminophenylthio)‐ N ‐aminophthalimide

A novel, asymmetric diamine, 3‐(4‐aminophenylthio)‐ N ‐aminophthalimide, was prepared from 3‐chloro‐ N ‐aminophthalimide and 4‐aminobenzenethiol. The structure of the diamine was determined via IR and 1 H‐NMR spectroscopy and elemental analysis. A series of polyimides were synthesized from 3‐(4‐aminophenylthio)‐ N ‐aminophthalimide and aromatic dianhydrides by a conventional two‐step method in N,N ‐dimethylacetamide and by a one‐step method in phenols. These polyimides showed good solubility in 1‐methyl‐2‐pyrrolidinone, m ‐cresol, and p ‐chlorophenol, except polyimide from pyromellitic dianhydride, which was only soluble in p ‐chlorophenol. The 5% weight loss temperatures of these polyimides ranged from 460 to 498°C in air. Dynamic mechanical thermal analysis indicated that the glass‐transition temperatures of the polyimides were in the range 278–395°C. The tensile strengths at break, moduli, and elongations of these polyimides were 146–178 MPa, 1.95–2.58 GPa, and 9.1–13.3%, respectively. Compared with corresponding polyimides from 4,4′‐diamiodiphenyl ether, these polymers showed enhanced solubility and higher glass‐transition temperatures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008