In this research, polyamide thin-film composite (TFC) membranes were fabricated by interfacial polymerization, and applied to pervaporative dehydration. To explore the relationship between the pervaporation performance and the properties of polyamide TFC membranes, such as morphology, chemical properties, hydrophilicity, surface roughness, and free volume properties, the membranes were characterized by SEM, XPS, ATR-FTIR, WCA, AFM, and VMSPB. Properties of various modified polyacrylonitrile (mPAN) membrane supports were measured; these supports were obtained by hydrolyzing asymmetric PAN membranes, as a result of immersing them in NaOH solution at different lengths of time. Results showed that the size and amount of pores on the mPAN membrane surface were decreased with the hydrolysis time, but there was practically no change in the macrovoids structure. From VMSPB results, S and R parameters and o-Ps annihilation lifetime (τ3) and intensity (I3) of mPAN membranes were reduced with the hydrolysis time, especially the R parameter and I3. Quenching and inhibition effects on formation and annihilation of positronium occurred in the mPAN membranes with longer hydrolysis time, due to their higher oxygen atomic concentration, which was associated with higher electron affinity, resulting in the decrease in R parameter and I3. Results demonstrated the effect of specific chemical environments on the free volume properties, and illustrated the relationship between chemical structure and positron data for the mPAN membranes. For the pervaporation performance in separating 90 wt% aqueous ethanol solution at 25oC, the permeation flux was reduced and the concentration of water in permeate improved with the hydrolysis time. To improve the pervaporation performance, novel TFC membranes were prepared by interfacial polymerization using new acyl chloride monomers, NTAC and TBAC, with the use of an mPAN membrane support at an optimal hydrolysis time. The effect of the monomer structure on chemical properties, microstructure, and pervaporation performance was investigated. Experimental data indicated that compared with the TETA-NTAC/mPAN membrane, the TETA-TBAC/mPAN membrane had a thinner polyamide layer with a denser structure, a rougher and lower degree of cross-linking surface. A possible reason was that the denser polyamide film formed on the mPAN membrane support, as a result of the TETA monomer reaction with the TBAC monomer, which had a higher reactivity with TETA due to the higher affinity between TETA and TBAC monomers, compared with NTAC, restricted the diffusion of the TETA monomer into the organic phase solution, resulting in a smaller thickness of the polyamide layer. The thicker and higher cross-linking polyamide layer of TETA-NTAC/mPAN membrane was the dominating factor affecting the membrane resistance during pervaporation, and caused a higher permeation flux (537 g/m2-h) and a higher concentration of water in permeate (98.2 wt%), despite its larger free volume size and higher free volume concentration. The mechanism of polyamide formation during interfacial polymerization is an important fundamental knowledge for understanding the properties of the polyamide layer of TFC membranes. Polyamide/PTFE TFC membranes were fabricated by interfacial polymerization using a porous PTFE membrane support with a hydrophilic or a hydrophobic surface. The polyamide layer surface at initial or final stages of interfacial polymerization could be controlled by the procedures of interfacial polymerization during the preparation of polyamide/PTFE TFC membranes. We found that growth of the polyamide film was affected by the surface property of the PTFE support. In the case of a hydrophobic PTFE membrane support, the growth direction of the polyamide film was inward, resulting in a thinner polyamide layer with a smoother surface, a higher cross-linking degree, and a less hydrophilic surface, which was formed at the initial stage of interfacial polymerization. On the other hand, the growth direction of the polyamide film on a hydrophilic PTFE membrane support was outward, leading to a thicker polyamide layer with a rougher surface, a lower cross-linking degree, and a more hydrophilic surface, which was formed at the final stage of interfacial polymerization. The differences in free volume properties of the polyamide formed at initial and final stages of interfacial polymerization were shown by means of VMSPB; results showed that the free volume size of the polyamide formed at the initial stage was larger than that at the final stage of interfacial polymerization. For the pervaporation in separating a 70 wt% aqueous IPA solution at 25oC, the polyamide/hydrophilic PTFE TFC membrane exhibited a higher performance than the TFC polyamide/hydrophobic PTFE membrane. Incorporating a novel inorganic layered material, graphene oxide (GO), into the polyamide layer of TFC membranes could increase the tortuosity and permeation routes of permeants, resulting in improving the pervaporation performance in dehydrating aqueous alcohol solutions. Results indicated that the GO with an exfoliated structure was dispersed in the polyamide layer, and the hydrogen bonding interaction between GO and polyamide inhibited the motion of the polyamide chain, resulting in decreasing the free volume of polyamide. For dehydrating a 70 wt% aqueous isopropanol solution at 70oC, permeation flux, concentration of water in permeate, and PSI of the resulting membrane with an optimal GO content in the polyamide layer were determined as 10396 g/m2-h, 99.0 wt%, and 2.40 ×106, respectively. The superior pervaporation performance showed potential for commercialization purposes. This research correlated the relationships between membrane characteristics and performance by means of analyzing the fundamental properties of the multilayered structure of TFC membranes, which were prepared by interfacial polymerization. Results showed excellent performance during the pervaporative dehydration. Understanding the relationships would then furnish significant information about the areas of membrane structure design and membrane performance prediction.