Synthesis and polymerization of 5-(methacrylamido)tetrazole, a water-soluble acidic monomer

The reaction of methacryloyl chloride with 5-aminotetrazole gave the polymerizable methacrylamide derivative 5-(methacrylamido)tetrazole (4) in one step. The monomer had an acidic tetrazole group with a pK_a value of 4.50 ± 0.01 in water methanol (2:1). Radical polymerization proceeded smoothly in dimethyl formamide or, after the conversion of monomer 4 into sodium salt 4-Na, even in water. A superabsorbent polymer gel was obtained by the copolymerization of 4-Na and 0.08 mol % N,N'-methylenebisacrylamide. Its water absorbency was about 200 g of water/g of polymer, although the extractable sol content of the gel turned out to be high. The consumption of 4-Na and acrylamide (as a model compound for the crosslinker) during a radical polymerization at 57 °C in D₂O was followed by ¹H NMR spectroscopy. Fitting the changes in the monomer concentration to the integrated form of the copolymerization equation gave the reactivity ratios r_4-Na = 1.10 ± 0.05 and r_acrylamide = 0.45 ± 0.02, which did not differ much from those of an ideal copolymerization. © 2002 Wiley Periodicals, Inc. J. Polym. Sci. Part A: Polym. Chem. 40.