Nanosecond dynamics of the macromolecules of methylcellulose in solutions and gels

Cooperative increase of relaxation times that describe nanosecond mobility of the polymer chains of methylcellulose in water on heating to 60 degrees C was studied by polarized luminescence. The position of this cooperative variation of relaxation times on the temperature scale is controlled by the concentration of polymer in solution (from 0.25 to 10-15 mg/ml). As the concentration is raised to the point of gelation, the growth becomes slower; this is related to the changes in the structure of supermolecular aggregates and the formation of quasi-equilibrium elements of the cross-linked structure. Large values of relaxation times are retained when an aqueous solution of methylcellulose is cooled from 60 to 40-30 degrees C. In organic solvents (DMF, DMAA), the values of relaxation times decrease on heating. This suggests that hydrophobic interactions play an important role in the formation of supermolecular aggregates in aqueous solutions.