Poly(epichlorohydrin) homopolymer (H-Hydrin) and poly[(ethylene oxide)-ran-(epichlorohydrin)] copolymer (C-Hydrin) are successfully chemically modified via azidation chemistry and characterized by 1H-NMR, 13C-NMR, FT-IR, GPC, DSC and TGA. UV cross-linking reaction is performed for modified Hydrin polymers and characterized by FT-IR, DSC, TGA, and gel content analysis. Gas transport properties of the initial and modified Hydrin polymers, and their derivatives cross-linked via nitrene reaction in the presence of UV irradiation are measured. The modified H-Hydrin homopolymers show higher permeabilities for CO2 and H2 than the unmodified H-Hydrin but lower CO2/N2, CO2/CH4 and H2/N2 selectivities. Likewise, the modified C-Hydrin copolymers have higher CO2 and H2 permeabilities than the unmodified C-Hydrin while maintaining similar CO2/N2, CO2/CH4 and H2/N2 selectivities. The increased gas permeabilities of Hydrin polymers after modification base on the decrease of glass transition temperatures (Tgs) which lead them to have higher polymer chain mobility and flexibility resulting in higher gas diffusivity. After cross-linking of modified C-Hydrin copolymers highly increased CO2/CH4 and H2/N2 selectivities and decreased CO2 and H2 permeabilities are observed.