Study of Polysulfone and Polyacrylic Acid (PSF/PAA) Membranes Morphology by Kinetic Method and Scanning Electronic Microscopy

Polymer propertiesPolysulfone (PSf) and poly (acrylic acid) (PAA) were supplied by Aldrich and dimethyl formamide (DMF) by Prolabo.All polymers and chemical products were used as supplied, without any further purification.Molecular weights of PAA and PSf were 450 000 and 26 000 g/mol, respectively. Membrane preparationPolysulfone (PSf) and Poly (acrylic acid) (PAA) were dissolved, separately, in dimethyl formamide (DMF) in a glass reactor equipped with a mechanical stirrer and thermostated at 90°C for over 3 hours.The PSf concentration was 17 (or 19) wt.% and that of PAA was 5 wt.%.Afterwards, both solutions were mixed together in known proportions, stirred for 30 min and de-bubbled.Such de-bubbled casting-solution was casted on a glass plate with a lab-made Gardner knife, dried in freeair for a known time (generally 20 seconds) and finally immersed in a coagulation-bath containing a sufficient volume of MilliQ water (18.2MΩcm) at 18°C.Membranes were thoroughly washed with water, and stored in a dilute sodium azide solution till their use. Kinetic measurementFive polymer-solutions with the same mass (2 g) and different composition (PSf/PAA 100/0, 96/04, 92/08, 89/11 and 83/17) were poured on a glass plate to get exactly a same surface area.Afterwards,