Tetrazolation of SAN25 and SAN30: To a solution of SAN25 (1.00 g, 5. Methylation of STz25 and STz30: STz25 (1.00 g, 2.2 mmol Tz units) was dissolved in DMF, followed by addition of K2CO3 (0.62 g, 4.4 mmol) and CH3I (0.56 mL, 8.8 mmol). The mixture was stirred overnight at room temperature and thereafter poured into deionized water to precipitate the polymer, which was isolated by filtration. The precipitate was then redissolved in THF and precipitated again. The resulting yellow solid was filtered, washed with deionized water, and dried in a vacuum oven at 50 ℃ overnight, resulting in a yield of 99%.