CARBONIZATION AND GRAPHITIZATION OF POLYIMIDE FILMS - POLYAMIDE ACID METHYL-ESTER OF PMDA PDA AS A PRECURSOR/

Polyamide acid was prepared from pyromellitic dianhydride (PMDA) and p -phenylenediamine (PDA) and was then reacted with NaH and methyl iodid e to transform into methyl ester having various degrees of esterificat ion. Polyamide acid methyl ester was also prepared by the polymerizati on between FDA and acid chloride of half-ester of PMDA. The cast films were imidized as fixed on glass substrate to give polyimide films hav ing slightly higher tensile moduli than those from polyamide acid, sug gesting that higher orientation along the film surface was achieved. I t should be noted that the polyimide films prepared by the latter meth od from the meta-rich configuration had considerably low modulus. The polyimide films were then carbonized by heating to 900 degrees C, and the electrical conductivity of the carbonized films was measured at ro om temperature. It was shown that the carbonized films from methyl est er have higher electrical conductivity than the films from correspondi ng polyamide acid. The carbonized films were further heated to 2800 de grees C for graphitization, and their degrees of graphitization and or ientation of the graphite crystallite as a function of esterification ratio were studied by x-ray diffraction measurement at room temperatur e and magnetoresistance measurement at liquid nitrogen temperature. Bo th measurements clearly indicate that the graphite films prepared from polyamide acid methyl ester have high degrees of graphitization and o rientation. (C) 1996 John Wiley & Sons, Inc.