Pendent Polyimides using Mellitic Acid Dianhydride. IV. Effect of Increased Zirconium-Pendent Group Content on Polymer Properties

For co-polyimides (PIs) of mellitic acid dianhydride, 1,3-aminophenoxybenzene and 4,4′-oxydiphthalic anhydride, Zr-pendent group content could be increased to 50% (mol) improving atomic oxygen (AO) resistance while retaining good film properties. Spectral data are consistent with expected structures. Intrinsic viscosities of 0.54—0.60 dL g—1 and average molecular weights of 111 000—122 000 g mol— 1 estimated from gel permeation chromatography confirm the polymeric nature of co-polyamic acid precursors. Nuclear magnetic resonance integrations and amounts of thermogravimetric analysis residue verify pendent group concentrations. Increasing Zr-pendent group concentration from 10 to 50% (mol) caused glass transition temperatures to increase (198—245 °C), decomposition temperatures to decrease (518—455 °C), and the number of film layers able to be fabricated prior to crack formation to decrease (10 to 8). These numbers of layers were much higher than those for other PIs with comparable Zr-pendent group concentrations. Increased pendent group concentration caused the amount of protective oxide layer formed upon AO exposure to increase.