Viscometric study on the compatibility of some water-soluble polymer–polymer mixtures

Dilute solution viscosity behavior of three water-soluble polymer mixtures has been studied at 20 °C. The ternary systems assayed are distilled water/sodium carboxymethylcellulose (CMC)/polyacrylamide (PAM), distilled water/methylcellulose (MC)/CMC, and distilled water/polyvinylpyrrolidone (PVP)/MC. The intrinsic viscosity and the viscometric interaction parameters have been determined for the binary (distilled water/polymer) and ternary (distilled water/polymer1/polymer2) systems. Degree of compatibility of these polymer systems was estimated on the basis of five criteria: (i) the sign of Δbm, (ii) the sign of Δbm′, (iii) the sign of Δ[η]m, (iv) sign of thermodynamic parameter α, and (v) the sign of modified thermodynamic parameter β. Based on the sign convention involved in these criteria, compatibility/miscibility was observed in CMC/PAM and MC/CMC systems and incompatibility/immiscibility in PVP/MC system. The FTIR analyses also support the obtained results. The miscibility/compatibility of all these systems is in accordance with the interactions between the unlike polymer chains rather than the polymer–solvent interactions.