The relationship between the chemical structure and thermal conversion temperatures of thermally rearranged (TR) polymers

An attempt was made to elucidate the relationship between chemical structure, in terms of glass transition temperature (Tg), and conversion temperature (TTR) 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 TTR was influenced by chain ridigity of o-hydroxypolyimides, and exhibited a linear relationship with Tg. Therefore, structure and thermal property of o-hydroxypolyimide should be considered when studying TR polymers to determine thermal conversion to polybenzoxazole.