Polymers show a wide range of characteristics like high impact and tensile strength, making them useful for different applications. Interpenetrating polymer networks (IPNs) created by combining two different polymers provides a novel avenue for improving overall polymer properties. In this research, acrylic-polyurethane based graft-interpenetrating polymer networks, which possess high mechanical properties, were synthesized. Chemical crosslinking points between the two polymeric systems were used to decrease the degree of phase separation. As one of the Ph.D. research topics, novel IPNs were synthesized with excellent transparency and 120% improvement in fracture toughness properties compared to traditional transparent materials such as Polymethylmethacrylate (PMMA) and Polystyrene (PS). The application of synthesized IPNs was broadened by increasing the percentage of PU in IPN. Synthesized IPN with excellent transparency shows the considerable potential of the novel flexible IPNs in transparent, high impact structural applications.
IPNs were also utilized as a matrix in carbon fiber-reinforced composites. Promising results demonstrated the potential for using novel acrylic-based IPNs in carbon fiber reinforced composites for demanding materials applications.
Moreover, the stress relaxation behavior of IPNs was modeled using the Prony series and a Generalized Maxwell model to incorporate spring-dashpots in the shear modulus. The MATLAB Curve Fitting tool and FEnics were manipulated for this purpose. A good match between experimental and simulated results was observed. The generated model is one of the first models for the stress relaxation behavior of IPNs. 
In the final chapter, graft semi-IPNs with excellent thermal properties and shape stability were synthesized. The results revealed the novel phase change materials' potential in thermal energy storage (TES) applications.

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