Absolute Molecular Weight Determination of Sodium Salt of Methacrylic Acid/Acrylic Acid-2-Isooctyl Ester/2-Acrylamido-2-Methylpropanesulfonic Acid Terpolymer by GPC/MALLS

The samples of sodium salt of methacrylic acid/acrylic acid-2-isooctyl ester/2-acrylamido-2-methylpropanesulfonic acid terpolymer (SSMAA) were synthesized by free radical solution polymerization. The absolute weight-average molar mass ( M w ) and polydispersity ( M w / M n ) of the polymers were successfully determined using aqueous-based gel permeation chromatography coupled with multiangle laser light scattering. The results show that mixed solutions of highly concentrated buffered salt (NaNO 3 or NaCl and NaH 2 PO 4 ) and organic solvent modifier (methanol) are needed to eliminate the undesirable interactions between polymer and polymer, and between polymer and stationary phase. Dynamic light scattering was first used to investigate the aggregation behavior of SSMAA in a variety of potential mobile phase compositions and screen the optimum compositions. The M w and M w / M n values of the three samples prepared with different amount of initiator are 13500, 5820, and 2490 g/mol and 1.52, 1.45, and 1.47, respectively.