Vertical alignment of carbon nanotubes in photo-curable polymer for multi-functional hybrid materials

Highlight • We reinforced the urethane acrylate-based polymer by vertically aligned MWNTs (VA-MWNTs) via dielectrophoresis process. • The addition of 0.001–0.005 wt% of VA-MWNTs optimally fortified the compressive strength of the polymer. • This lightweight polymer can be developed into various materials, including bulletproof materials and vehicle surfaces including aircraft. Carbon nanotubes (CNTs) are nanomaterials with excellent mechanical strength, electric conductivity, and low weight. Interestingly, vertically aligned CNTs show much higher mechanical and electrical properties than randomly networked CNTs, because CNTs are much more resistant to axial impacts than lateral impacts; this study suggests an efficient process to produce vertically aligned multi-walled carbon nanotubes (VA-MWNT)-photocurable polymer hybrid materials. VA-MWNTs can fortify the mechanical properties of polymer composites even with very small amounts of MWNTs in the composite. Previous studies have produced VA-MWNT–polymer hybrid materials by coating polymers on MWNT forests synthesized in the vertical direction. However, this method cannot be extended to the large-scale production of hybrid polymers because of the limited area of substrates for the synthesis of the MWNT forests, and because the synthesis requires a complex and expensive process. We arranged MWNTs in the vertical direction in VA-MWNT-polymer mixtures in a short process via electrophoresis. Subsequently, UV irradiation for a few minutes completely cured the photocurable polymer while the MWNTs were fixed in the vertical direction. The VA-MWNT-polymer showed a 17% higher compressive force than the polymer itself and interestingly, a 49% higher compressive force than the polymer with randomly dispersed MWNTs, indicating that the orientation of MWNTs in polymer composites affects their curing behavior as well as mechanical strength. These polymer-MWNT composites can be used as-is or coated on other materials and can be expected to exhibit enhanced mechanical properties in various applications.