Effect of molecular weight on the rheological properties of atactic poly(vinyl alcohol)/dimethylsulfoxide/water solution

This article describes the molecular weight effect of atactic poly(vinyl alcohol) (a-PVA) on the rheological properties of 7.5, 10.0, and 12.5 g/dL solutions of a-PVA with number-average degrees of polymerization (P_n) of 4000 and 1700 in dimethylsulfoxide/water mixture. a-PVA with a P_n of 1700 solutions exhibited almost Newtonian flow behavior, whereas high molecular weight a-PVA, with a P_n of 4000 solutions, exhibited shear-thinning behavior. On the plot of storage and loss moduli of a-PVA with a P_n of 1700 solutions, the dynamic storage modulus of a-PVA, with a P_n of 1700 solutions, was smaller than the dynamic loss modulus over the frequency range of 10^-1 to 10² rad/s. However, the dynamic storage modulus of a-PVA, with a P_n of 4000 solutions, was smaller than the dynamic loss modulus in the sol state and, in the postgel state, the dynamic storage modulus became larger than the dynamic loss modulus, indicating the evolution of viscoelastic solid properties.