Mesoscale pore structures have been of great interest due to the potential applications of filtration, catalysis, adsorption, and separation processes. However, most studies have focused on materials fabricated in the bulk or thin films. Moreover, the formation of polymer nanoscopic materials having designed mesoporous structures and surface topographies are remaining a challenge. Fabrication of mesoscale pore one-dimensional nanostructures was investigated herein by using thermal nanoimprint lithography. The materials used of polystyrene/polyvinyl alcohol (PS/PVA), high-density polyethylene (HDPE)/PVA and HDPE/PVA-Glycerol blends, were prepared by advanced polymer mixing machine of the high shear process. The ultra-fine dispersed phase of PVA embedded in PS and HDPE matrices was able to be prepared by this methods. One-dimensional polymer nanostructures with 100 nm diameter and 10-70 µm length were fabricated using the thermal nanoimprint machine with anodic aluminum oxide (AAO) template. After the selective removal of the PVA segment, the mesoscale pore one-dimensional nanostructures with 10-40 nm were generated owing to; (1) controlling the surface-induced phase separation between AAO-PVA and AAO-Glycerol, and (2) apply the foaming process using supercritical carbon dioxide (scCO2). The obtained mesoscale pore one-dimensional nanostructures show the hydrophobic and superior oleophilic properties. The impact behaviors of water droplets on the replicated surfaces present the bouncing behavior as the rubber-ball-like, but the oil droplet immediately penetrates through the nanostructures. This result demonstrates the possible potential of one-dimensional nanostructures in the water/oil separation process.