Enhanced Ca2+ binding with sulfonic acid type polymers at increased temperatures

This paper focuses on the influence of Ca2+ binding and temperature on the molecular size and hydrophilicity of sulfonic acid type polymers. Two different molecule structural polymers employed were sodium polystyrene sulfonate and poly(2-acrylamido-2-methyl-1-propane-sulfonic acid). The effect of CaCl2 and high temperatures on the polymer molecules was explored with gel permeation chromatography, calcium ion selective electrodes, Fourier transform infrared spectroscopy, transmission electron microscopy, dynamic light scattering, rheology, and surface tension measurements. The results indicate that high temperatures promote the binding of calcium ions with the two polymers and also lead to dehydration of the polymer chains. The variation rule of molecular size, apparent viscosity and surface tension of the two sulfonic acid type polymers depended on their molecular structure.

Possible explanation for the effect of heat treatment and CaCl2 addition on the structure and distribution of PSS in aqueous solution. The black curves represent the PSS molecules and the orange circles indicate the calcium ions.Figure optionsDownload as PowerPoint slideHighlights
► The combination of Ca2+ on PSS increased with temperatures and salt concentrations.
► The effect of Ca2+ and temperatures on polymers depended on the molecular structure.
► The hydrophobicity of PSS increased with concentrations of salt and temperatures.
► Some aggregates formed in the PSS system with high salt by heated treatment.