Oxygen plasma-resistant phenylphosphine oxide-containing polyimides and poly(arylene ether heterocycle)s: 2

Abstract

Phenylphosphine oxide-containing poly(arylene ether imide)s, poly(arylene ether quinoxaline)s, poly(arylene ether benzoxazole)s and poly(arylene ether benzothiazole)s were prepared by reacting the appropriate difluoro heterocyclic compound with bis(4-hydroxyphenoxy-4′-phenyl)phenylphosphine oxide. The polymers exhibited glass transition temperatures from 209 to 255°C and inherent viscosities from 0.35 to 1.34 dl g-1. Thin-film tensile properties measured at room temperature and 177°C exhibited tensile strengths of 10.2-15.8 and 6.0-9.0 ksi (∼ 70.3-108.9 and ∼ 41.4-62.1 MPa), respectively, and tensile moduli of 340-381 and 204-365 ksi (∼ 2.34-2.63 and ∼ 1.41-2.52 GPa), respectively. Unoriented thin films of these phenylphosphine oxide-containing polymers were subsequently exposed to a radiofrequency-generated oxygen plasma under vacuum along with Kapton® HN. To assess the resistance of the materials to the oxygen plasma, the weight losses of the films were monitored as a function of exposure time. Phenylphosphine oxide-containing poly(arylene ether benzoxazole)s and poly(arylene ether benzothiazole)s exhibited weight-loss rates that were 38-190 (1-2 orders of magnitude) times slower than that of Kapton® HN. Phenylphosphine oxide-containing poly(arylene ether quinoxaline)s exhibited weight-loss rates only slightly slower (1-7 times) than those of Kapton® HN. The changes in surface chemistry of the exposed films were subsequently examined using X-ray photoelectron spectroscopy. In most cases, the phosphorus and oxygen near the surface exhibited increases in relative concentration and the photopeaks shifted towards higher binding energies. These changes are indicative of the formation of phosphate-type species. In addition, their limiting oxygen indices were calculated from char yields at 850°C in nitrogen utilizing a reported method. For the most part, the incorporation of phenylphosphine oxide groups did not substantially increase the limiting oxygen indices. © 1995.