Cobalt phthalocyanine sheet polymer showed very high-thermal stability with a maximum polymer decomposition temperature of 500 degrees C in air, and 860 degrees C in nitrogen, with char yield of 85% at 800 degrees C in a nitrogen atmosphere. MS and GC-MS studies of the cobalt phthalocyanine sheet polymer were conducted at high temperatures ranging from 500 to 1000 degrees C. Tentative mechanisms are proposed for its modes of fragmentations and the most probable degradation products were identified by GC-MS. (c) 2005 Elsevier B.V. All rights reserved.