Amphiphilic random copolymers with charged groups as membrane selective layers


Ilin Sadeghi


Ilin Sadeghi, Ayse Asatekin

Author Affiliation: 

Tufts University


Membranes are a promising technology for many applications such as chemical processing, pharmaceutical manufacture, bio-analytical separations and industrial desalination/water purification. Nanofiltration (NF) is a low pressure-driven (5-40 bar) filtration process with the separation characteristics between reverse osmosis (RO) and ultrafiltration (UF). Nanofiltration membranes with the pore size of about 0.5-2 nm have wide applications in water softening, pharmaceuticals and food industry. Currently, only a small number of polymers are used in membrane applications. Specifically, most NF membrane selective layers are polyamides. These selective layers are susceptible to fouling, have poor chlorine resistance and low chemical and thermal stability. Therefore, we seek alternative polymeric materials that can overcome these drawbacks. In this project, we study the manufacture and performance of membranes whose selective layers are composed of random copolymers of hydrophobic and charged monomers. We synthesized a random copolymer of 2,2,2-trifluroethyl methacrylate (TFEMA) and methacrylic acid (MAA), PTFEMA-r-PMAA using free radical copolymerization method, and prepared membranes by coating porous supports with thin layers of these polymers. When cupric acetate was added to the membrane casting solution together with the copolymer, we could enhance the water permeation through the membrane to about ~8 L/ (from the initial value of about ~3 L/ Promising rejections for different organic dye molecules (positive, negative and neutral with the diameter of 8 to 8.5 °A) and monovalent and multivalent salts with concentration ranging from 1 mM to 10 mM were also obtained. These results indicate that this family of amphiphilic copolymers could potentially be useful as new NF membrane chemistries.