The next decomposition stage was found to occur between 140 ℃ and 285 ℃ for STz25 and between 165 ℃ and 290 ℃ for STz30. This stage can be attributed to the decomposition of the pendant tetrazole groups. The final stage involved the decomposition of the polymer backbone, which started at around 310 ℃ for STz25 and 330 ℃ for STz30. The glass transition temperatures, as summarized in Table , was determined from the DSC data (Figure ) and was found to be 69.6 ℃ for STz25 and 109.9 ℃ for STz30. The difference suggests a strong hydrogen bonding between the tetrazole units of the latter, which shifted the Tg towards higher values. The X-ray diffraction (XRD) patterns of the pristine SAN25/SAN30 exhibit two characteristic halos at 2θ = 13° and 2θ = 20°, corresponding to d-spacing values of 6.8 Å and 4.4 Å, respectively (Figure ). In the XRD patterns of the tetrazole-functionalized STZ25/STZ30 polymers, which were nearly identical, only the peak at 2θ = 20° was observed, which appears broader. This indicates that the introduction of tetrazole units further enhances the mostly amorphous nature of the polymers.