Several aromatic polyisoimides were prepared, and their third-order nonline
ar susceptibilities, chi((3))(-3 omega, omega, omega, omega), were measured
by optical third-harmonic generation. Obtained chi((3)) values are in the
order of 10(-12) e.s.u. at a fundamental wavelength of 1907 nm. The largest
value, chi((3)) = 3.4 x 10(-12) e.s.u., was Obtained for the polyisoimide
prepared from pyromellitic dianhydride (PMDA) and p-phenylenediamine (PDA).
Thermal stability of the polyisoimide prepared from PMDA and PDA was teste
d. The contents of isoimide structure decreases due to thermal imidization
above 200 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.