Water‐soluble copolymers. V. Compositional determination of random copolymers of acrylamide with sulfonated comonomers by infrared spectroscopy and C13 nuclear magnetic resonance

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Abstract
Compositional analyses of random copolymers of acrylamide with sodium‐2‐sulfoethyl methacrylate and with sodium‐2‐acrylamido‐2‐methylpropane sulfonate have been performed utilizing elemental analysis, infrared spectroscopy, and C13 NMR. A mathematical method involving nitrogen to sulfur ratios has been developed to eliminate errors which often arise from associated water in hydrophilic copolymers. The ratios of infrared absorbances at 1043 cm−1 and 1664 cm−1 were used to determine the composition of AM—NaAMPS copolymers; likewise, absorbance ratios at 1040 cm−1 and 3200 cm−1 were utilized for determination of the AM—NaSEM copolymer composition. Carbon‐13 NMR spectra of the copolymers were also obtained, and characteristic peaks were utilized to quantitate copolyer composition. The results obtained by elemental analyses, infrared spectroscopic studies, and NMR were in excellent agreement. These techniques are of great value for determining composition of hygroscopic copolymers which can crosslink or form strong intramolecular hydrogen bonds, often precluding further characterization.