Effect of Temperature on Polyelectrolyte Expansion of Lignosulfonate

Abstract

The temperature effect on the polyelectrolyte expansion of sodium lignosulfonate (SL) was studied in the range of 20 to 38 °C. A narrow molecular-weight distribution fraction of sodium lignosulfonate was first obtained by gel column chromatography, which was suitable for the hydrodynamic radius (Rh) measurement by dynamic light scattering (DLS). Dynamic light scattering experiments showed that the hydrodynamic radius of sodium lignosulfonate decreased with increasing temperature. Using a quartz crystal microbalance (QCM) and atomic force microscopy (AFM), it was found that the adsorbed sodium lignosulfonate film lost water with increasing temperature and reabsorbed water with decreasing temperature. Surface tension and contact angle experiments showed that there were more hydrophobic groups on the surface of the sodium lignosulfonate molecule as the temperature increased. It can be concluded that the sodium lignosulfonate molecule shrank and became more hydrophobic with increasing temperature. Analysis suggests that the decreasing of the hydrogen-bond interactions between the sodium lignosulfonate molecule and water molecules with increasing temperature is the primary reason for the molecular conformation change of sodium lignosulfonate.

Keywords

• Sodium lignosulfonate
• Temperature
• Polyelectrolyte expansion
• Molecular conformation