This study describes the synthesis of poly(N-isopropylacrylamide) (PNIPAM) via free radical polymerization, the preparation of physical blends containing sodium carboxymethylcellulose (CMC) and PNIPAM in aqueous solution, at total polymer concentrations of 2 and 6 g/L in different compositions, and applies rheology to investigate interactions between PNIPAM and CMC compared to pure polymers, in aqueous solution. Rheological measurements indicated thermothickening behavior for the 50 % PNIPAM-50 % CMC physical blend in aqueous solution, at 6 g/L, as viscosity rose when temperature was increased to a range of 25-40 A degrees C. Similar thermothickening behavior was observed for the 25 % CMC-75 % PNIPAM physical blend in solution, at a total polymer concentration of 2 g/L. These results provide new information for preparing physical blends in aqueous solutions exhibiting thermothickening behavior, indicating that this behavior depends on total polymer concentration and composition of the mixture.