DNA-Assisted Dispersion of Multi-Walled CNTs in Epoxy Polymer Matrix
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DNA-Assisted Dispersion of Multi-Walled CNTs in Epoxy Polymer Matrix Susanna Laurenzi1, Matteo Sirilli1, Mirko Pinna1 and M. Gabriella Santonicola2,3 1 Department of Astronautic Electrical and Energy Engineering, Sapienza University of Rome, Via Salaria 851-881, 00138 Rome, Italy 2 Department of Chemical Materials Environmental Engineering, Sapienza University of Rome, Via del Castro Laurenziano 7, 00161 Rome, Italy 3 Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands Corresponding authors: [email protected], [email protected] ABSTRACT The homogeneous dispersion of carbon nanotubes (CNTs) in a polymer matrix is a critical parameter that significantly affects the electrical and mechanical properties of CNT-based composite materials, and represents an important challenge to overcome during the manufacturing process of these materials. In our work we used double-stranded DNA to facilitate the dispersion of multi-walled CNTs in solution prior to the integration in epoxy resin PRIME 20 LV. Composites containing DNA-wrapped CNTs were prepared using sonication at 0.5 wt.% CNT loading and the dispersion level in the composite CNT/PRIME 20 LV was observed under an optical microscope. Nanoindentation experiments were conducted to determine the local mechanical properties of the CNT/PRIME 20 LV composites films after cure, showing a significant improvement in their distribution across the sample surface as a result of the enhanced CNT dispersion by DNA. An electrical test to assess the stability of the CNTs dispersion in the resin was developed by measuring the conductivity of the composite mixture before cure in time. Results of the electrical measurements indicate that the CNT/PRIME 20 LV mixture with DNA-wrapped CNTs is stable for several days after preparation. INTRODUCTION Nanocomposites based on carbon nanotubes are extensively investigated in different fields of research for their manifold exceptional properties. CNTs possess high strength, high modulus and very interesting electric and thermal features for a wide range of applications [1-5]. However, the performance of nanocomposites is strictly related to the CNTs dispersion in the polymer matrix. Enhanced dispersion of CNTs in a polymer matrix greatly improves the mechanical, thermal, electrochemical, optical and hydrophobic properties of the composite materials. The main problem that is encountered in reinforcing a polymer matrix with CNTs is to obtain a homogeneous dispersion thus avoiding that the CNTs turn into localized defects in the nano-reinforced composites. What makes CNTs dispersion extremely difficult is their large specific surface and large aspect ratio characteristic of the nanotubes [6-7]. In fact, the mutual attraction of the CNTs, due to van der Waals forces, drives their aggregation into clusters, even after mechanical disentanglement processes employed during fabrication. In order to overcome these problems, different approaches h
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