Scheme 2. Schematic of synthetic route for 4-arm-PEG-Mal. Scheme 2 outlines the synthetic procedure for producing 4-arm-PEG-Mal. To summarize, a solution of 4-arm PEG 10K (1.00 g, 0.1 mmol) and GMI (0.074 g, 0.48 mmol) in dichloromethane was cooled to 0°C, after which a solution of DCC (0.107 g, 0.52 mmol) in dichloromethane was added. The resulting mixture was stirred at room temperature for 24 hours, filtered, and then the filtrate was precipitated using diethyl ether. The precipitate was subsequently dried under vacuum to a constant weight and stored at -20°C.