The FT-IR data of the pristine SAN25 and SAN30 copolymers exhibited small bands at approximately 2240 cm -1 , indicating the presence of nitrile groups as shown in Figure and 2b, respectively. After the tetrazolation procedure, the absorption bands could no longer be seen, supporting the successful conversion of nitrile groups into tetrazoles. Additionally, the FT-IR spectra of STz25 and STz30 showed new bands around 1555 cm -1 . These bands are specific to tetrazole groups, further confirming the successful transformation of nitrile groups into tetrazoles. The 1 H NMR spectra of STz25 and STz30, as shown in Figure and 2d, respectively, reveal two distinct regions with overlapping multiplets from about 1.0-3.0 ppm, which correspond to the aliphatic protons of both styrene and acrylonitrile units and a set of multiplets in the region of 6.5-7.6 representing the aromatic protons of the styrene unit. The spectra were nearly identical to that of the pristine polymers (see Figure ). Due to the lack of 1 H NMR trackable protons in the functional groups of STz25 and STz30, full methylation of the tetrazole units was carried out to estimate the degree of conversion. The methylation reaction is wellknown to occur in nearly quantitative yield, and the degree of tetrazolation could therefore be estimated by comparing the peak integral of the distinctive -CH3 group at 4.07 ppm to the peak integral of the styrene part, as summarized in Table . After casting from DMF, the STz25 and STz30 membranes appeared transparent and the crosssectional SEM micrographs, as shown in Figure , indicate a homogenous and dense structure. The thermogravimetric curves and derivatives of weight loss of SAN25/SAN30 and STz25/STz30 are shown in Figure and S4b, respectively. The TGA curves of the pristine SAN25/SAN30 reveal a major onset of degradation at around 360 ℃, following a single-step process. During this step, both the polystyrene and polyacrylonitrile segments of the polymer decompose simultaneously. Interestingly, the thermal stability was not influenced by the compositional differences. In contrast, the thermal behavior of STz25/STz30 polymers exhibits three distinct regions of mass loss. The first region, ranging from room temperature up to 140 ℃ for STz25 and 160 ℃ for STz30, is associated with the release of water molecules bonded to the highly hygroscopic tetrazole units, and eventual DMF residuals from the membrane casting.