Wei Cheng

Abstract

The goals of this research are to synthesize novel two and four-component pendent polyimides by attaching the zirconium complex to the respective polymer backbones, and then to compare their characteristics, e.g. thermal properties, atomic oxygen resistance, and film properties, with those of previous students of Dr. Illingsworth, Derek Chow and Wei Wang. Our work focuses on increasing the atomic oxygen resistance of polyimides by increasing their pendent group concentrations. This result can best be achieved by increasing the flexibility of the polymer backbone, which also lowers glass transition temperature (Tg), improves polyamic acid solubility, and, thus, improves processibility. The novel four component "parent" polyamic acid (PAA) based on 1,3-aminophenoxybenzene (APB), 3,4'-oxydianiline (3,4'-ODA), 4,4'-oxydiphthalic anhydride (ODPA), and mellitic acid dianhydride (MADA) was synthesized in freshly dried solvent l-methyl-2-pyrrolidone (NMP), and the Zr(adsp)(dsp) pendent groups attached in the presence of dicyclohexylcarbodiimide (DCC). Portions of each solution, i.e. parent and pendent PAA, were treated with nonsolvent or cast into films. After precipitation, the parent polyamic acid and Zr(adsp)(dsp) pendent polyamic acid powders were thermally imidized using three different processing conditions: 1) 100C, 200C, and 300C for one hour each, 2) 100C for an hour followed by 380C for five minutes, or, 3) 100C for an hour followed by 380C for thirty minutes. The resulting parent and Zr(adsp)(dsp) pendent polyamic acid films were imidized using the same three processes as above. Some of the films of Zr(adsp)(dsp) pendent polyimide were exposed to atomic oxygen in a plasma asher. The synthesized parent and Zr(adsp)(dsp) pendent polyamic acids and polyimides were characterized by thin layer chromatography (TLC), fourier transform infrared (FT-IR), proton nuclear magnetic resonance ('H NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), intrinsic viscosity (IV) determination, laser light scattering (LS), refractive index, solvent resistance testing, optical microscopy, and scanning electronic microscopy (SEM), before and after atomic oxygen exposure for the latter two. TLC results indicate that no free zirconium complexes remain in the Zr(adsp)(dsp) pendent polyamic acid solution. Spectroscopic results support the conclusion that the structures obtained are consistent with the proposed ones. Polyimides were prepared using three different processing conditions. Tgs were higher for the 380C processed material. Decomposition temperatures of pendent polyimides and parent polyimide are all very high, which means that they possess very high thermal stability. Both the intrinsic viscosity results and LS results indicate that a moderate degree of polymerization occurred, and the weight average molecular weight of the pendent polymers is 48,829g/mol. All of the films passed the solvent resistance test in acetone, methyl ethyl ketone, toluene, chloroform, tetrahydrofuran (THF) and THF/methanol mixture for 30 minutes followed by a fingernail crease. The pictures taken by optical microscopy and SEM and visual observation indicate that the atomic oxygen erosion of the zirconium pendent polyimide films leaves a white chalky coating on the surface, which is due primarily to the formation of zirconium dioxide and which retards the further oxidization of polyimide. The eroded Zr(adsp)(dsp) pendent polyimide surface is similar to that observed for analogous three component Zr pendent polymers prepared by D. Chow and W. Wang. For single layer films, the resistance time of Zr(adsp)(dsp) pendent polyimide is more than four times longer than that of the parent polyimide. The maximum tetra(acetylacetonato)zirconium(IV), Zr(acac)4, concentration in the four component parent polymer was determined. Film cracking upon imidization and transparency of films were the criteria used to make this determination. No transparent imidized films can be obtained if the concentration of Zr(acac)4 is 30% by mole or above.

Library of Congress Subject Headings

Polyimides--Synthesis; Polyimides--Analysis; Polyimides--Thermal properties; Zirconium compounds

Publication Date

8-1-2001

Document Type

Thesis

Department, Program, or Center

School of Chemistry and Materials Science (COS)

Advisor

Terence, Morrill

Comments

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: TP1180.P66 C436 2001

Campus

RIT – Main Campus

Download

Share

COinS