Atomic oxygen resistant Zr pendent polyimide based on 1,3-aminophenoxybenzene

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Title: Atomic oxygen resistant Zr pendent polyimide based on 1,3-aminophenoxybenzene
Author: Chow, Derek
Abstract: We wish to evaluate Zr pendent aromatic polyimides based on oxydiphthalic anhydride (ODPA), 1,3-aminophenoxybenzene (APB) and mellitic dianhydride (MADA) as atomic oxygen resistant materials. Eight poly(amic acid) solutions in Nmethylpyrrolidone (NMP) with different anhydrides ratios were synthesized, and four of the eight poly(amic) acids allowed to react with the complex (4-amino-N,N '- disalicylidene- l,2-phenylenediaminato)(N.N '-disalicylidene- 1,2- phenylenediaminato)zirconium(IV), Zr(adsp)(dsp), in the presence of dicyclohexylcarbodiimide (DCC). The resulting non-pendent polyamic acids and Zr pendent polyamic acids were cast onto glass substrate followed by thermal imidization. Characterization of polyamic acids and polyimides were accomplished by Thin Layer Chromatography (TLC), Fourier Transform Infrared (FT-IR), Proton Nuclear Magnetic Resonance (!H NMR) and Gel Permeation Chromatography (GPC). Their thermal properties were investigated by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). TLC results indicate that no free Zr complex remains following the DCC reaction. Spectroscopic results of Zr(adsp)(dsp), polyamic acids and polyimides were consistent with their proposed structures. GPC results indicate that a moderate degree of polymerization occurred. The incorporation of the ether groups and meta amino position along the polymer backbone decreased the glass transition temperatures vs. analogous polymers without APB. Their Tg's fell in the ranges 64.1 to 74.6 C, 57.6 to 83.1C, 188.3 to 242.9C and 198.5 to 245.3C for polyamic acids, pendent polyamic acids, polyimides, pendent polyimides, respectively. The zirconium pendent polyimides were less thermally stable than the parent polyimides, being stable up to 455.53- 518. 15C and 525.61- 555.43C, respectively, and affording char yields of 0.993-12.52 % for pendent polymers and 0% for non-pendent polymers at 700C in air. Multilayer films of the Zr complex pendent polyimides were made. The maximum number of layers that were made were 10, 10, 8 and 8 for PI(ODPA/APB/10 mol % MADA), PI(ODPA/APB/20 mol % MADA), PI(ODPA/APB/30 mol % MADA) and PI(ODPA/APB/50 mol % MADA), respectively. All fully imidized films passed the solvent resistance test which involved immersion in acetone, methyl ethyl ketone, toluene, 1-mefhyl-pyrrolidinone (NMP), dimethylsulfoxide (DMSO) and chloroform for one hour followed by a fingernail crease. Their atomic oxygen resistance was studied by Scanning Electronic Microscopy (SEM) before and after atomic oxygen erosion in a plasma asher. The SEM of Zr pendent polyimide film shows substantial erosion occurred in select regions, giving a "pitted" appearance.
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Date: 2000-05

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