Carbonization of boron containing polyimide films - B-N bond formation

Two types of boron containing polyimide (Kapton type) film were prepared either by adding dihydroxyphenylborane (DPB) to polyamic acid [mixing method] or by using diaminodiphenyl ether having a boron containing functional group (DDE-B) to prepare polyamic acid [substitution method]. Formed polyimide films containing boron were carbonized at 600 - 1200 degrees C, By doping boron into the precursor polyimide, preferential formation of B-N bonds in carbonized films was observed and appreciable amounts of nitrogen were chemically trapped in the carbon film even after carbonization at 1200 degrees C, The polyimide prepared by the substitution method gave uniform carbon films in composition and structure, though DDE-B is not simply synthesized and didn't polymerize to high degree. The polyimide prepared by the mixing method gave non-uniform carbon films. but the process was very simple and possible to increase boron content by using different boron compounds. (C) 1999 Elsevier Science Ltd. All rights reserved.