Quantifying the Dependence of Molecular Weight on Intrinsic Viscosity for Acrylamide and 2-Acrylamido-2-methylpropanesulfonate (Co)polymers

Acrylamide-2-acrylamido-2-methylpropanesulfonate (AM-AMPS) copolymers are important water-soluble polymers widely used across diverse industries. The molecular weight plays a crucial role in determining the characteristics of their aqueous solutions, thereby directly affecting their performances in applications. However, the rapid and accurate determination of their molecular weight has long been a critical challenge for industry. In this work, by systematically measuring the intrinsic viscosities ([η]) and weight-average molecular weights (<i>M</i>_w) (calibrated by static light scattering) of AM-AMPS copolymers with 50 mol % AMPS in 0.5 M NaCl solution, a universal Mark-Houwink equation was established for the first time: [η] = 0.0104 × <i>M</i>_w^0.74 mL/g (<i>R</i>² > 0.99). This equation was validated across at least the <i>M</i>_w range of (0.82-16.1) × 10⁶ g/mol and shown to be applicable to (co)polymers with AMPS contents from 0 to 100 mol %. This work offers a rapid, reliable tool for <i>M</i>_w determination, effectively addressing a longstanding challenge in the production and quality control of AM-AMPS copolymers.