Preparation And Properties Of Quarternary Ammonium Salt Copolymer/Polyethersulfone Blend Membrane

Polyethersulfone（PES）,as an excellent membrane material,is widely used in membrane separation in recent years.However,owing to its hydrophobicity,PES membrane is easily polluted during the separation process.A method of blending is usually adopted to improve its fouling resistance.Polymeric quaternary ammonium salt is a commonly used organic antibacterial agent due to its properties of sustained-release,long-acting,low toxicity,safety,powerful bactericidal activity,good chemical stability and easy processing.In this paper,a polymerizable quaternary ammonium salt was synthesized with 4-vinylbenzyl chloride and N,N-dimethyldo decylamine,and then its copolymer with acrylonitrile（PQA-co-AN） was prepared by free radical solution polymerization.Then,the compatibility of PQA-co-AN and PES and the rheological behavior of PQA-co-AN/PES blend solution were studied.Finally,the PQA-co-AN/PES blend membrane was successfully prepared by a phase inversion method using a DMAC/H₂o system as a coagulation bath.The influences of membrane-forming conditions on the membrane performance such as mechanical properties, antibacterial property,water flux,porosity and retention level were discussed. The PQA-co-AN/ PES blend system might have partially compatible from the thermodynamical view.This was confirmed by the measurements of polarized light microscope,Ubbelohde dilution viscometry and SEM. Moreover,the compatibility was found worse when the content of each component was similar.The rheological results showed that the PQA-co-AN/PES blend solution was a shear-thinning fluid.The non-Newtonian index decreased with the increase of the blend solution concentration and the PQA-co-AN content, and increased with the increase of temperature.It was found that the structure and properties of the blend membranes were affected by the solution concentration,pre-evaporation time and coagulation bath,etc.With the increase of solution concentration,the water flux and porosity of PQA-co-AN/PES membranes decreased,but retention level to albumin bovine increased.With the increase of PQA-co-AN content, the water flux and porosity of PQA-co-AN/PES membranes decreased at first and then increased,and the retention level to albumin bovine increased. The water flux and porosity of blend membrane exhibited a minimum when the mass fraction of PQA in the casting solution was *.1.5%.With the increase of pre-evaporation time,the water flux of PQA-co-AN/PES membranes decreased at first and then increased,but the retention level to albumin bovine was on the opposite trend,and the porosity basically remained unchanged.The minimal water flux and the maximal retention level both occurred at the pre-evaporation time of 40 seconds.The water flux and porosity decreased with the increase of coagulation bath concentration, but increased with the coagulation bath temperature.The retention level to albumin bovine increased when the coagulation bath concentration increased, and it decreased when the coagulation bath temperature increased.The SEM observation suggested that the changes of PQA-co-AN/PES membranes’ structure coincided with that of its properties.The mechanical tests showed that the fracture strength and breaking elongation rate of PQA-co-AN PES membranes were gradually decreased with the increase of PQA-co-AN content.The antibacterial tests showed that the antibacterial activity of the blend membrane to Staphylococcus aureus and Escherichia coli was higher than that of PES membrane,and it increased with the increase of PQA-co-AN content.This paper is a tentative work,which could provide some theoretical references to the preparation of the PQA-co-AN/PES antibacterial blend hollow fibre membranes.