Molecular Design of Polymer Nanocomposite Membranes for CO2 Separation

This dissertation describes preparation and characterization of graphene oxide (GO) incorporated polymeric membranes by adjusting the molecular structure for efficient CO2 separation. GO as a nanofiller in polymer matrix were used for inducing interlayer space for gas transport and providing preferential CO2 sorption sites. The intrinsic physical and chemical properties of GO/polymer mixed matrix membranes were characterized in molecular level. Also, the polymeric support membranes were tailored regarding surface porosity and pore size to fabricate thin film composite membranes for scalable and industrial membrane gas separation applications. Chapter 1 describes the background of polymeric membranes for gas separation, which is necessary to establish a strategy to overcome the challenging issues. Recent progress in nanocomposite membranes for CO2 separation were reviewed regarding several types of nanofiller in this chapter. Chapter 2 describes the microphase separation in poly(ether-amide) block copolymers and the structural design of mixed matrix membranes by adding poly(ethylene glycol) with low molecular weight and well-dispersed monolayer GO sheet. Since 0D (fullerene) or 1D (carbon nanotube) are inappropriate in mixed matrix membrane due to small surface area, GO with high aspect ratio is expected to show remarkable enhancement in separation property. Also, the gas transport properties were evaluated in terms of the degree of crystallinity and fractional free volume of mixed matrix membranes. Furthermore, addition of organic and inorganic materials were compared to the theoretical models to optimize the gas separation property. Chapter 3 demonstrates the importance of surface porosity and pore size in fabrication of thin film composite membranes by preparing highly porous polyacrylonitrile (PAN) support layer by nonsolvent induced phase separation (NIPS) method. PAN has advantages over thermal and chemical resistance, however, pore size and porosity of membrane surface should be controlled to apply gas separation membrane. In particular, surface property of prepared membranes were analyzed with both empirical and theoretical method. Conclusions part presents summaries of this work and directs how to utilize the aforementioned materials in the future for applying them in industrial level.Maste