Pendent polyimides using mellitic acid dianhydride. III. The effect of pendent group functionality on polymer properties

Abstract

Methyl, methoxy, and nitrile (cyano) functional groups were incorporated into the metal-organic pendent group of a co-polyamic acid, co-PAA [(3,4 0 -ODA/ ODPA) 0.9 (3,4 0 -ODA/{MADA-p-Zr(adsp)(Rdsp)}) 0.1 ], in various locations to investigate their effects on polymer chain interactions and film quality. Proton nuclear magnetic resonance and gel permeation chromatography (GPC) performed on solutions of these products were consistent with the expected 10% (mol) functionalized pendent polymeric structures. Thermogravimetric analysis performed on ether-precipitated samples revealed little functional group effect on imidization temperature (decreases of 5-8 C), but showed a somewhat-greater effect on decomposition temperature (decreases of 6 C for the 3-methoxy derivative to 28 C for the methyl derivative). Differential scanning calorimetry performed on imidized powder samples showed that glass transition temperatures increased with the addition of the functional groups from 2 C for the methyl derivative to 19 C for the 3-methoxy derivative. Imidized films were solvent resistant, transparent, and flexible, with the nitrile derivative least susceptible to crack formation. Light scattering results revealed that the nitrile derivative had the lowest second virial coefficient of the functional groups tested and formed aggregates at room temperature in NMP with n ¼ 2, thus rationalizing its superior film forming properties. Results of contact angle measurements and atomic oxygen exposure of functionalized pendent co-PI films are included.