Production of graphene oxide and polymer based nanocomposite microsieves via breath figure method

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2017
Kıratlı, Ayşe Elif
Porous polymer films are used in various different fields such as electronics, sensors, biomedical, catalysis, and separation. Breath figure (BF) is a method of obtaining porous polymers via a self-assembly process based on water condensation. In this process condensed water droplets can be regularly arranged on surface depending on process conditions. They continue to grow or sink until all solvent is evaporated. After complete evaporation, honeycomb shaped porous polymeric films are obtained. Amphiphilic copolymers or end group functionalized polymers are often used for obtaining such structures. It is difficult to form regular honeycomb patterned films via BF method from linear hydrophobic polymers such as polysulfone (PSF). PSF itself is not very effective in stabilizing water droplets during the BF process even though such films could be very useful for membrane based separation applications. In such circumstances, a hydrophilic additive is needed for droplet stabilization. Since vi hydrophilic additives reduces the interfacial tension, regular surface morphology can be easily obtained. In this work, poly(PEGMA) grafted graphene oxide (GO) is proposed as a stabilizer for obtaining porous PSF films via breath figure process. GO sheets were synthesized and then decorated with hydrophilic polymer chains of poly(PEGMA) via atom transfer radical polymerization (ATRP). Obtained product was used as a hydrophilichydrophobic additive in order to create PSF based honeycomb structures via BF method. By the optimization of BF experimental parameters, porous PSF films were obtained and their performance for microfiltration applications was assessed. The results showed that poly(PEGMA) grafted GO facilitated regular pore formation during BF process and resulted in highly uniform honeycomb patterned PSF films. Average pore sizes of the obtained porous films could be varied from 2 to 7 microns and the pore depth could be varied 2 to 17 microns depending on process conditions. Filtration performance of the porous films was tested by yeast filtration and percentage rejection was calculated as 88.2 ± 5.7.