Properties and Potential Applications of Poly(arylene ether benzimidazole)s

Abstract

As part of a NASA program on high performance polymers for potential aerospace applications, poly(arylene ether benzimidazole)s (PAEBIs) are under evaluation. The polymers are prepared by the aromatic nucleophilic displacement reaction of 5,5′-bis[2-(4-hydroxyphenyl)benzimidazole] with activated aromatic difluorides in a polar aprotic solvent using potassium carbonate at elevated temperatures under nitrogen. Based on preliminary screening of various material properties, two polymers were selected for more extensive evaluation. An isophthaloyl-containing PAEBI was evaluated for potential use as an adhesive and composite resin matrix. Controlled molecular weight versions of this material exhibited a good combination of processability and high unidirectional composite properties up to 232°C. This polymer also exhibited excellent adhesion to copper and polyimide, and moderate adhesion to titanium. A phosphine oxide-containing PAEBI was screened for potential use on spacecraft in low Earth orbit where resistance to atomic oxygen is required. Thin films of this material were exposed to an oxygen plasma under vacuum and the weight loss of the film was monitored as a function of exposure time. Relative to uncoated Kapton®HN film, the phosphine oxidecontaining poly(arylene ether benzimidazole) film exhibited significantly lower weight loss rates. In addition, this material exhibited a non-linear weight loss rate as compared to Kapton® HN film which exhibited a linear weight loss rate. Upon exposure to the oxygen plasma, the phosphine oxide-containing poly(arylene ether benzimidazole) formed a phosphate-type surface coating as evidenced by x-ray photoelectron spectroscopy.