A partially foamed lattice structure based on synthetic polymers was considered as a functionally graded materials due to their unique properties. In this study, a copolymer is manufactured to be porous functional materials by physical foaming technology, using carbon dioxide. Through morphological characterization, using scanning electron microscope, we identified a potential to fabricate partially foamed structures with micropores. We showed that variation of post-foaming temperature can tune the pore size distribution in the range of 0.9 to 30 μm. Thermal data of the foam grid from differential scanning calorimeter showed some shifts in glass transition, cold crystallization, and melting points. Mechanical strength and thermal conductivity were also measured to find rationale of thermal insulation with tunable mechanical strength and to elucidate the actual 3D lattice foam of a copolymer.