Carbon nanotubes (CNTs) are a relatively new allotrope of carbon that possess very unique and exciting physical characteristics. However, much is still unknown regarding their physical structure and chemical reactivity. The focus of this dissertation is to utilize the chemical modification of these filamentous carbon structures as a probe to investigate the structure and reactivity of carbon nanotubes. Also discussed is the ability of CNTs, once chemically modified, to interact with specific polymer matrices and how the addition of modified and unmodified CNTs affects the physical properties of these matrices.