Laser light-scattering study of polyacrylamides with and without hydrolyzation in 0.35M KH2PO4 aqueous solution

Abstract

Both the hydrolyzed and unhydrolyzed polyacrylamides with different molar masses were characterized in 0.35M KH2PO4 aqueous solution at 25°C by laser light scattering (LLS). The Laplace inversion of precisely measured intensity-intensity time correlation function leads to an estimate of the characteristic line-width distribution G(Γ) which can be further reduced to a translational diffusion coefficient distribution G(D). A combination of the measured weight-average molar mass Mw and G(D) enables us to establish a calibration of D (cm2/s) = (4.46 ± 0.02) × 10−5M−0.50±0.003. Using this calibration, we convert each G(D) into a corresponding molar mass distribution. The calculated Mw from such a molar mass distribution is reasonably close to the measured Mw from static LLS. Most important is that when 0.35M KH2PO4 aqueous solution is used as solvent, both the hydrolysed and unhydrolysed polyacrylamides can be represented by an identical calibration; namely, in 0.35M KH2PO4 aqueous solution, the polyelectrolytes effect in the hydrolysed polyacrylamides has been suppressed. Therefore, the hydrolysed polyacrylamides can be characterized as a normal neutral polymer in 0.35M KH2PO4 aqueous solution, which makes a routine characterization of the hydrolysed polyacrylamides much easier. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1755–1760, 1997