Synthesis and Characterization of Alginate Methacrylate

Alg-MA was synthesized utilizing an anhydrous reaction to control the degree of methacrylation (DOM).^{28 -29 (link)} Sodium alginate was rendered soluble in anhydrous DMSO through an ion exchange with DTAB. Aqueous solutions of sodium alginate (1%, w/v) and DTAB (2%, w/v) were prepared and slowly mixed while stirring at 1000 rotations per minute (rpm). The precipitate was washed in DI water and lyophilized. A 1% (w/v) alginate-DTA/DMSO solution was reacted with MA in the presence of a catalyst, DMAP, for 24 hours at room temperature. The solution was hydrolyzed through extensive dialysis in 0.2 M sodium phosphate dibasic salt solution followed by further dialysis in DI water. Alginate methacrylation was confirmed using ¹H-NMR spectroscopy, (Bruker AVANCE III 500 MHz high-field NMR spectrometer) by the presence of methacrylate (6.25, 5.75 ppm) and alginate methyl resonances (2.0 ppm). A 1% (w/v) polymer solution in D₂O was analyzed at room temperature, spinning at 20 Hz for 16 scans.^{28 , 30 (link)} The DOM was quantified by peak integration and calculation of the ratio between of the methyl protons at 2.0 ppm and the newly formed methylene protons of methacrylate at 5.75 ppm and 6.25 ppm.^{30 (link)-31 (link)}