Fantastic Entanglements between Polyelectrolytes in Solutions

We study the entanglement properties of flexible and semiflexible polyelectrolytes sodium polystyrene sulfonate and sodium carboxymehtyl cellulose. In dilute salt-free and excess-salt solutions these polymers adopt rod-like and expanded coil conformations respectively. The solvent’s ionic strength has a large impact on the conformation of polyelectrolytes, and the number of binary interchain contacts, quantified through the intrinsic viscosity and osmotic pressure respectively. While adding salt leads to a large decrease in polymer size, it does not affect their entanglement density and entanglement crossover. This contradicts packing models of polymer entanglement and suggests that the density of binary contacts in solution is not affected by the solvent quality. Based on this observation, we work out the reptation dynamics of polyelectrolytes in salt-free solution, which differ appreciably from earlier models.