Hyperbranched Polymers Modified Carbon Nanotubes And Nanocomposite Research

Covalent and non-covalent functionalization of carbon nanotubes (CNTs) are recently developing as the most powerful tools enabling their processing and assembly from solution and polymer resin matrices. In this thesis, we reported modification of CNTs with polymer through covalent and non-covalent methods. Furthermore, we hope to explore possible applications of these functionalized CNTs in high performance nanocomposites.1. Surface modification is a general and efficient approach to improve the compatibility of carbon nanotube (CNT) with various matrixes. Here we report the modification of multi-wall carbon nanotube (MWCNT) with hyperbranched polymer which contains UV reactive functional groups through a covalent method. The modification promotes the incorporation of CNT into UV-curable resin, and when cured under UV irradiation to form a homogeneous film, the CNT will be chemically bonded with the matrix by crosslinking photopolymerization. For the unique mechanical properties of CNT, the mechanical properties of the cured MWCNT/UV-curable resin film were greatly improved compared with pure resin film as indicated by the increasing of Young's modulus, tensile strength, and toughness.2. The hyperbranched polyester (Boltorn^TMH20) was modified by maleic anhydride and then polystyrene (H20-MAh-PSt) to form amphiphilic micelles in water. The single-wall and multi-wall carbon nanotubes (SWCNTs and MWCNTs, respectively) were encapsulated in the formed micelles through non-covalent interactions. The formed structures were confirmed by FTIR, NMR, GPC, and XPS analysis. The dispersion and aggregation behaviors were observed by TEM and UV-vis and Raman spectroscopic analysis. The results showed that the dispersion performance of the obtained micelle-encapsulated carbon nanotubes in water was greatly improved compared to the pure carbon nanotubes. From the TEM observation, the individual SWCNT structure and the uniform polymer coating around the surface of SWCNT were seen after crosslinking. The Raman spectroscopic measurements also demonstrated that for the crosslinked samples, no effect occurred associated with concentration-dependent carbon nanotube aggregation.3. The multi-wall carbon nanotube (MWCNT) / gold and platinum nanoparticle composites were individually prepared by binding the nanoparticles to the surface of thiol-modified MWCNTs. The TEM images indicated that the gold particles possess a diameter of 4-6 nm, whereas the platinum particles possess a smaller diameter of 2-3 nm. All the metal particals were distributed uniformly on the walls and ends. The formation of MWCNT / Au and MWCNT /Pt nanoparticle composites was further confirmed by UV-vis absorption and Raman spectroscopy. The nitrogen adsorption-desorption approach was used to investigate the surface area and cyclic voltammetry and showed that two composites demonstrate significant electrocatalytic activity for oxygen reduction.