The goal of this research is to increase the metal-organic concentration in Kapton-like polyimides (PIs) to achieve increased atomic oxygen (AO) resistance while retaining desirable film properties. Co-polyamic acid (PAA) precursors were prepared using a novel polymer building block, mellitic acid dianhydride (MADA), to provide sites for pendent group attachment. Attachment of an amino group-functionalized zirconium complex to the co-PAA precursors was facilitated by a stoichiometric amount of dicyclohexylcarbodiimide. The viscous solutions which resulted were characterized by thin layer chromatography (TLC), viscosity, and gel permeation chromatography (GPC), or treated with excess poor solvent to precipitate powder samples, or cast onto glass slides and heated to produce imidized films. Powder samples were dissolved in deuterated solvent for proton nuclear magnetic resonance analysis, or characterized by thermogravimetric analysis and differential scanning calorimetry. Film samples were characterized by Fourier transform infrared and by scanning electron microscopy (SEM) before and after exposure to atomic oxygen in a plasma asher. The spectroscopic data are consistent with the expected amic acid and imide, pendent and non-pendent structures. TLC, viscosity and GPC results confirm the polymeric nature of the pendent and non-pendent co-PAA precursors, with inherent viscosities (<0)of 0.76 and 0.65 and weight average molecular weights (Mw) estimated to be 61 000 and 138 000 Dalton, respectively. As expected, visual and SEM inspections of pendent and non-pendent co-PI films reveal extensive surface roughening upon exposure to AO, with the former developing a white surface layer known from model compound studies to be predominantly zirconium dioxide. Additional reports describing the effects of polymer structure and pendent group concentration on film properties and AO resistance are in preparation.

Using mellitic acid dianhydride to prepare Zr‐containing pendent copolyimides (co‐PIs) is currently being evaluated as a means of further increasing Zr concentration and atomic oxygen resistance while retaining other desirable film properties. The immediate objectives en route to this ultimate goal are: (1) to address the increased tendency of copolyamic acids (co‐PAAs) to undergo gelation during polymerizations and upon addition of dicyclohexylcarbodiimide during the Zr appending reactions, and (2) for multilayer films, to increase the number of layers that can be applied prior to crack formation. To accomplish these two objectives, a targeted structure–property study has been performed, holding the Zr concentration constant at 10 mol %. The polymer starting materials chosen for this investigation include PMDA and OPDA (dianhydrides), and 4,4′‐ODA, 3,4′‐ODA, and 1,3‐APB (diamines). The spectroscopic data for all polymer products are consistent with the expected amic acid, imide, pendent, and nonpendent structures. Thin‐layer chromatography, viscosity, and gel permeation chromatography (GPC) results confirm the polymeric nature of the Zr pendent and nonpendent co‐PAA precursors, with intrinsic viscosities (η0) of 0.86–0.46 for the former and 0.76–0.38 for the latter. Weight‐average molecular weights are estimated from GPC to be 115,400–436,000 g/mol for the former and 38,300–111,200 g/mol for the latter. While there was little observable effect of structure change on tendency to form gel, APB‐containing Zr pendent copolyimide had the lowest glass transition temperature and allowed the largest number of layers to be cast in a single film without cracking (10 layers) of the pendent copolyimides in this study. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1641–1652, 2007

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