The solution was purged with nitrogen for 15 min. Next, methacryloyl chloride (3.0 mL, 0.03 mol) was added dropwise to the solution under stirring and cooling in an ice bath. The ice bath was removed after the heating discontinued and the reaction was running for 3 days at room temperature. Afterwards, the reaction mixture was filtered and the supernatant was purified by alumina column. With vitamin E (0.18 g) added to prevent premature cross-linking, the solution was concentrated and precipitated in diethyl ether twice. After drying under vacuum overnight, 51.0 g of a white powder was obtained. The methacrylation conversion was determined to be 82% by 1 H NMR spectroscopy. In some cases (e.g., PEGDMA 2k and 4k), extraction was used instead of alumina column purification.