Salting-in behavior of isotropic and anisotropic aqueous hydroxypropylcellulose solutions

Salts with large polarizable ions are capable of salting-in complex aqueous polymer solutions exhibiting microstructure, thereby inducing changes in the phase behavior and properties of the solutions. In this work, the dynamic rheological properties of isotropic and mesomorphic hydroxypropylcellulose (HPC) in aqueous media have been investigated in the presence of one such salt, guanidine thiocyanate (GuSCN). Addition of this salt to isotropic aqueous HPC solutions is found to induce an increase in the magnitude of the elastic shear modulus (G'). At HPC concentrations above the isotropic --> mesophase transition, however, addition of GuSCN results in a substantial reduction in G' due to microstructural changes in the chiral nematic HPC mesophase. This reduction in G' indicates that the microstructure of a water-soluble polymer exhibiting supramolecular organization can be tailored through salting-in, and is likewise expected to facilitate the commercial processing of HPC at high solids concentrations.