Poly(amic acid) was synthesized by means of low-temperature-solution polymerization of 3,3'-dihydroxybenzidine and pyromellitic dianhydride in N,N-dimethylacetamide. The precursor polymer was heat-treated at different temperatures to create a polybenzoxazole (PBO) through a polyimide (PI). PI containing the hydroxyl group was rearranged by decarboxylation with heat treatment, resulting in a fully aromatic PBO. Hexadecylamine was used as an organophilic alkylamine in organo-clay, We have tried to clarify the intercalation of heterocyclic polymer chains to hexadecylamine-montmorillonite (C-16-MMT) and improve tensile properties. It was found that the addition of only a small amount of organo-clay was enough to improve the mechanical properties of PBO. Maximum enhancement in the ultimate tensile strength for PBO hybrids was observed for the blends containing 4% C-16-MMT. The initial modulus monotonically increased with further increases in the C-16-MMT content. (C) 2001 John Wiley & Sons, Inc.