This thesis presents the results of a study on the blends of an aliphatic crystallizable polyamide (nylon 6/6) and trace quantities of a polar non-crystallizable diluent (poly(vinylpyrrolidone)). This study is based on the preliminary findings of Keith et al. who reported striking morphological changes in nylon 6/6 upon addition of small amounts of poly(vinylpyrrolidone) (PVP). The melting behavior of pure nylon 6/6 was also studied during the course of this investigation. The melting behavior of nylon 6/6 was studied using a differential scanning calorimeter (DSC). Samples were isothermally crystallized at various temperatures from the melt. Subsequent DSC analysis showed the presence of three distinct melting endotherms. The behavior of these three endotherms was studied as a function of the crystallization temperature (T_C), annealing time, and DSC heating rate. X-ray studies (small and wide angle) and hot stage optical microscopy studies were also carried out to determine the cause of the multiple endotherms. The influence of addition of PVP on the crystal morphology of nylon 6/6 was studied using DSC, x-ray and hot stage photomicroscopy. The addition of PVP has a dramatic effect on the spherulitic morphology of nylon. The addition of PVP to nylon caused a striking reduction in the nucleation density of spherulites, modification of lamellar organization in spherulites (as evidenced by the occurrence of banding), and modification of interlamellar spacings. / Master of Science