Cellulose nanofibers (CNFs) are a sustainable and environmentally friendly material which can be used as a highly versatile reinforcing agent in polymer nanocomposites. This thesis presents a novel method to produce CNFs from Midwest agricultural residues and the work done to integrate CNFs into hydrophobic matrix elastomer, SBR. Cellulose nanofibers produced from Midwest agricultural residuals showed a promising morphology with diametrical dimensions on the nanometer scale. Superior reinforcement effect was also observed when these nanofibers were incorporated in PEO based nanocomposites. Additionally, high performance rubber (SBR) nanocomposites which incorporated various functionalized CNFs were produced. These rubber nanocomposites displayed heightened mechanical properties and showed significant potential to replace traditionally formulated rubber reinforced with non-environmentally friendly carbon black.