Synthesis of pH-Sensitive PDMAEMA Hydrogel

Poly [2-(dimethylamino) ethyl methacrylate] (PDMAEMA) is a kind of pH-sensitive polymer and it has been widely used in the biomedical field due to several advantageous features such as non-toxicity and biocompatibility [41 (link),42 (link)]. The PDMAEMA hydrogel was prepared through the radical aqueous solution polymerization route. A total of 4 g 2-(dimethylamino) ethyl methacrylate (DMAEMA) (Sigma Aldrich, Shanghai, China) was passed through a basic alumina column (DIKMA, Beijing, China) before using, in order to remove its inhibitor. A DMAEMA monomer was dissolved in 16 mL de-ionized water, then 0.06 g Methylene-bis-acrylamide (MBA, cross-linking agent) (Sigma Aldrich, China) and 0.04 g potassium persulfate (KPS, initiator) (Sigma Aldrich, China) were added. The solution was mixed under a nitrogen atmosphere for 10 min to remove oxygen, then the sealed reaction tube was kept for 24 h at a 60 °C atmosphere for the completion of polymerization. After the reaction, the tube was cooled to room temperature and the plunger was opened to take out the sample, with subsequent cutting of the prepared gel into small pieces. The pieces were soaked and washed with de-ionized water, while changing the water continuously to remove the unreacted monomer, cross-linking agent and initiator. After 3 days, the gel was taken out and dried for later use.