Current technology of polymer nanocomposites (PNC) emphasizes the need for fundamental understanding of the links between manufacturing method and macro-scale properties in order to engineer processing and performance of PNCs. The manufacturing method is one key variable that dramatically defines interfacial interactions on the nano-scale and thus the properties of polymer near the interface of nanomaterial/polymer or interphase, level of dispersion and the crystallization behavior of semi-crystalline PNCs. These factors in particular govern reinforcing mechanisms at the interface and consequently impart important properties to PNCs. The current approach to manufacturing PNCs involves trial and error with elaborate, costly and time consuming experimental characterization of PNCs. Therefore, a deep insight into the links among manufacturing method, interfacial interactions and bulk properties is essential in order to design and fabricate PNCs with engineered performance. The main goal of this study was to provide a better understanding of the effect of manufacturing methods on the macro-scale properties of PNCs, with a focus on the role of interfacial interactions, that can lead to fabrication of PNCs with multifunctional performance. The objectives of this research were to: i) determine the detail correlations among manufacturing method, nano- and microstructure and macro-scale properties of multifunctional exfoliated graphite nanoplatelets/polyamide 12 polymer nanocomposites with enhanced mechanical and electrical performance through systematic manufacturing and experimental methodologies, ii) understand correlations among nano-scale interfacial interactions, physical and structural properties of the polymer at the interface and macro-scale behavior of PNCs, and iii) evaluate effect of manufacturing method on electrical behavior of PNCs with directionally dependent performance. This study demonstrated key correlations among manufacturing techniques, interfacial interactions and macro-scale properties of PNCs. A methodology was introduced to understand and determine the characteristics of a complex constrained region produced at the interface of nanomaterials and polymer in semi-crystalline PNCs. Finally, the study illustrated superior electrical and morphological properties of selective laser sintering (SLS) processed parts over injection molded PNCs and thus confirmed the capability of SLS in the development of electrically conductive PNCs that exhibit multifunctional performance. In conclusion, the study provided an insight into the links among process, nano-scale interfacial interactions and microstructure to better understand effects of manufacturing technique on macro-scale properties of PNCs, which enables fabrication of conductive PNCs with multifunctional performance.