Preparation and properties of modified POD membranes by polycarboxylic acids copolymerization

A series of X-POD polymers were prepared by condensation reaction of terephthalic dihydrazide and four different polycarboxylic acids in polyphosphoric acid (PPA) as solvent, and the corresponding membranes were formed by phase inversion method. The modified X-POD polymer structures have changed from linear structure to multidimensional network structure, which has great influence on the quality and performance of the membranes. The membrane structures were characterized by FTIR, and the thermal stability of the samples was determined by Thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). The ultraviolet transmittance and fluorescence properties of membranes were tested by ultraviolet spectrophotometer. The crystallinity and orientation of the samples were observed by X-ray diffraction (XRD). The surface and cross-sectional morphology of the membranes were evaluated by scanning electron microscope (SEM). Additionally, the oxidation and water absorption properties of the membranes were collected, and the mechanical properties of the membranes were tested. Overall, X-POD membranes show good mechanical properties, chemical inertness and thermal stability. The quality and mechanical properties of X-POD membranes demonstrated varying degrees of improvement. Notably, the mechanical properties of II-POD and III-POD membranes were enhanced by 244.52% and 203.66%, respectively. X-POD membranes exhibit high strength and excellent toughness, rendering them a highly promising material for membrane applications in the market.