Thermal Behavior of VARIOUS sulfone-based diimid-diacids Solvated with Polar Organic Solvents

Abstract

Thermal analysis techniques were performed to reveal ‘crystalline solvate’ behavior between organic compounds and polar solvents. Diimide-dicarboxylic acid (DIDA) was formed by reacting 3,3'-diaminodiphenylsulfone (3,3'-DPS) or 4,4'-diaminodiphenylsulfone (4,4'-DPS) with trimellitic anhydride (TMA) in some polar solvents (PSv). The products could crystallize upon cooling in a polar solvent media to form a solvate containing a finite quantity of solvents, leading to what can be termed as ‘crystalline solvates’ (CS). This study has demonstrated that sampling techniques in TG and DSC must be kept to be as similar as possible, which is a critical point in practices of thermal analysis techniques. DSC analysis revealed that there are two endothermic peaks in the CS, with the lower one being the de-solvate temperature of CS (Td) at which the solvated solvent molecules were removed, and the higher peak being the melting point of the de-solvated DIDA (Tm). Td was found to vary with the types of polar solvents and structures of DIDA. The TG result indicated that most of the sulfone-based DIDA-CS contained 2 moles of solvent per mole of solvate. X-ray analysis revealed that different crystalline structures were found for DIDA-CS solvated with different solvent molecules, but all de-solvated DIDA possessed the same crystal unit.