| dc.description.abstract | Efficient liquid-phase separation technologies such as adsorption and membrane separation are promising to replace conventional energy-demanding separation processes. These techniques are also advantageous to deal with formidable water pollution challenges. This dissertation focuses on porous polymeric and hybrid materials that are developed as sorbents and membranes for selective adsorption, organic solvent nanofiltration, and water / oil separation applications.
The first chapter introduces benchmark industrial separation technologies and current challenges in this field from the perspective of materials research. The mechanisms of selective adsorption and membrane separation are discussed. Recent advances in the applications of polymeric materials in organic solvent nanofiltration and water / oil separation are reviewed, with representative examples discussed in detail.
Chapter II reports a novel and highly efficient synthetic approach to porous polymer networks, through aldol triple condensation using methanesulfonic acid as catalyst and solvent. Aromatic porous polymer networks were obtained with high porosity and narrow pore size distribution. The porous material demonstrated fast and selective adsorption of organic small molecules in aqueous solution. In addition, the pristine composition of the reaction mixture was solution processable and enabled membranes fabrication for organic solvent nanofiltration applications, as described in Chapter III. These porous polymer network membranes exhibited retained structural integrity and organic solvent nanofiltration performance with molecular-sieving selectivity and high permeability, in the presence of either a strong acid or strong base for extensive period.
Chapter IV reports a hybrid membrane made of a stainless-steel mesh coated with zinc oxide tetrapod crystals and polydimethylsiloxane. The presence of micrometer-size tetrapod crystals provided a rough surface, which amplified the hydrophobicity of polydimethylsiloxane, so that the water contact angle of the membrane was greatly increased. The hydrophobic and oleophilic membrane rejected water while letting the oil permeate through, suitable for potential applications in efficient water / oil separation.
Overall, this dissertation reports several examples of porous polymers and hybrid materials prepared through new synthetic and fabrication approaches. The separation mechanisms in a variety of scenarios were identified as either size-exclusion or wettability. Fundamental principles of structure-property relationships were used to guide the materials design and development. The selectivity, durability, and wettability for separation functions were tailored by engineering the porosity, aromaticity, and surface roughness of the materials, respectively. Further enhancement of the separation performances for real-life applications is anticipated through continued chemical and materials engineering approaches along this direction. | |
