Replication of One-Dimensional Composite Nanostructures with Enhanced Mechanically Robust and Thermal Conductivity

Abstract

Nano–engineered surfaces inspired by nature of gecko feet and cicada wings were widely mimicked to replicate the architectural nanostructures on various polymer films. These natural surfaces often provide multifunctional properties and advanced material surfaces such as adhesiveness, hydrophobic surfaces, bio–medical applications, nanosensing materials, catalytic scaffold materials, and energy storages. In this study, vertically aligned composite nanostructures (VACNs) of polystyrene (PS)–graphene nanoplatelets (GNPs) (1.0–5.0 wt/wt%) were precisely replicated by thermal nanoimprint with anodic aluminum oxide (AAO) template. Implications of the reinforced nanofiller on nanostructured surface properties including physical, chemical, thermal, and mechanical properties were investigated. The one-dimensional (1D) composite nanostructures of PS–GNPs with the length of 10–70 µm and diameter of 100 nm were fabricated, resulting the enhancement of surface wetting ability in the water contact angle from 87±3o (flat film) increased to 132±2o. The increase in surface properties including friction coefficient, surface durability (See Figure 1, left), surface modulus and hardness of the PS–GNPs nanostructures as compared with the neat PS nanostructure, were also respectively obtained. The glass transition temperature (Tg ) of PS–GNPs nanostructures was shifted toward about 1.0 to 4.0 oC as compared with their bulk composites because of the immobilization of the polymer chain owing to confinement and surface interfacial interaction effects at the nanoscale within graphene and AAO template. Interestingly, it was found that thermal conductivity of PS–GNPs nanostructures became higher than their composite films due to the 1D property caused by the control of in–plane orientation of GNPs nanofiller within AAO (See Figure 1, right). The maximum thermal conduction of 1D nanostructure of PS–GNPs 5.0 wt/wt% up to 1.28 W/m.K can be obtained in this study. Higher thermal stability of the PS–GNPs nanostructures than that of PS nanostructure was also shown.