###### Abstract  
Mesoscale pore one-dimensional (1D) nanostructures, or vertically aligned porous nanostructures (VAPNs), have attracted attention with their excellent hydrophobic properties, ultra\(-\)high surface area, and high friction coefficient, compared to conventional vertically aligned nanostructures (VANs). In this study, we investigate the replication of VAPNs produced by the thermal nanoimprint process using anodic aluminum oxide (AAO\({}^{2}\)) templates (100 nm diameter). Polystyrene/poly(vinyl alcohol) (PS\({}^{1}\)/PVA) blends, prepared by the advanced melt-mixing process with an ultra-high shear rate, are used to investigate the formation of porosity at the nanometer scale. The results reveal that domain size and mass ratios of PVA precursors in the PS matrix play a dominant role in the interfacial interaction behavior between PS\({}^{1}\)-PVA-AAO\({}^{2}\), on the obtained morphologies of the imprinted nanostructures. With a PVA nanodomain precursor (PS\({}^{1}\)/PVA 90/10 wt%), the integration of PVA nanodroplets on the AAO\({}^{2}\) wall due to the hydrogen bonding that induces the phase separation between PS\({}^{1}\)-PVA results in the formation of VAPNs after removal of the PVA segment. However, in the case of PVA microdomain precursors (PS\({}^{1}\)/PVA 70/30 wt%), the structure transformation behavior of PS\({}^{1}\) is induced by the Rayleigh instability between PVA encapsulated around the PS\({}^{1}\) surfaces, resulting in the PS\({}^{1}\) nanocolumns transforming into nanopepapods composed of nanorods and nanospheres. adhesive surfaces using humidity control [9; 10]. Moreover, VAPNs with high value-added have been effectively applied in the fields of energy storage and nanosensing materials [5], and filters [9]. For these reasons, VAPNs are regarded as a novel class of frontier nanomaterials in both industry and academia. A versatility technique for fabricating VAPNs is the templating method using nanoporous anodic aluminum oxide (AAO) assisted by solvent-wetting and thermal melt-wetting methods. The control of surface-induced phase separation behaviors in the AAO pores is crucial for these techniques. A great deal of research has attempted to improve these methods to be faster, cheaper, more precise, less toxic, and more scalable, which are in conflict with the fundamentals of the solvent-wetting and thermal melt-wetting methods [11; 12; 13; 14]. With the successful development of polymer engineering technologies, the direct patterning method of thermal nanoimprint is an alternative method to replicate the VAPNs because of its high replication capability with rapid speed, zero-solvent use, high precision and reproducibility. For example, one-dimensional polymer nanofiber arrays with various lengths, diameters, aspect ratios, and patterns, were successfully produced by nanoimprint machine using AAO templates [15]. However, the direct fabrication of VAPNs using the nanoimprint method with AAO templates has not been achieved yet. Therefore, it is a great challenge to develop the thermal nanoimprint process by controlling the phase separation of polymers in the AAO templates. Study on the various polymer material behaviors at the nanoscale of AAO templates based on the solvent-wetting and thermal melt-wetting methods have been successfully clarified. By using these wetting methods, many publications have reported that polymer behaviors in AAO templates, consist of the flow ability and its gradients, phase separation behaviors, transformation behaviors, and so on. [PERSON] et al. [16; 17; 18] studied flowing gradients by using various polymer blends in AAO templates. With the larger pore size of AAO, it promoted phase separation of polymer blends. In the case of polymer blends with the same value of surface energy, polymer flow gradients were strongly dependent on the glass transition temperature (\(T_{g}\)) and polymer melt viscosity which are related to the polymer chain mobility.