An attempt was made to elucidate the relationship between chemical structure, in terms of glass transition temperature (T-g), and conversion temperature (T-TR) of thermally rearranged polybenzoxazole membranes, by analyzing DSC and TGA data for a total of 15 sets of o-hydroxypolyimides and copolyimides, derived from two experimental and four commercial structurally different diamines, as well as four different dianhydride monomers. Our research revealed that T-TR was influenced by chain ridigity of o-hydroxypolyimides, and exhibited a linear relationship with T-g. Therefore, structure and thermal property of o-hydroxypolyimide should be considered when studying TR polymers to determine thermal conversion to polybenzoxazole. (C) 2012 Elsevier Ltd. All rights reserved.