The focus of this dissertation is to develop a fundamental understanding of process-structure-property relationship in two different classes of polymers: semi-crystalline Ultra High Molecular Weight Polytetrafluoroethylene (UHMWPTFE) and amorphous glassy double network (DN) epoxies. Conventional melt processing techniques such as extrusion and injection molding cannot be applied to UHMWPTFE due to its very high melt viscosity (1010-1011 poise). Therefore, UHMWPTFE is industrially processed by a modified metallurgy technology-sintering. However, the fundamental mechanism for UHMWPTFE sintering is unknown. Further, this process is highly time consuming, cost inefficient and hinders the recyclability of the material. The first part of this dissertation aims at developing experimental techniques for studying the sintering process in-situ and thereby elucidates the molecular mechanism associated with UHMWPTFE sintering. Further, the effect of different fluoropolymer additives and process conditions on the sintering behavior will be studied. The second part of this dissertation aims at developing asymmetric double network epoxies where the two networks are distinct both in terms of chemical stiffness and crosslink density and correlating this complex network architecture with thermal and non-linear mechanical properties.