Viscosity‐molecular weight relationship for cellulose solutions in either NMMO monohydrate or cuen

The intrinsic viscosities, [η], of nine cellulose samples, with molar masses from 50 × 10 3 to 1 390 × 10 3 were determined in the solvents NMMO*H 2 O ( N ‐methyl morpholin N ‐oxide hydrate) at 80°C and in cuen (copper II‐ethlenediamine) at 25°C. The evaluation of these results with respect to the Kuhn–Mark–Houwink relations shows that the data for NMMO*H 2 O fall on the usual straight line in the double logarithmic plots only for M ≤ 158 10 3 ; the corresponding [η]/ M relation reads log ([η]/mL g −1 ) = –1.465 + 0.735 log M . Beyond that molar mass [η] remains almost constant up to M ≈ 10 6 and increases again thereafter. In contrast to NMMO*H 2 O the cellulose solutions in cuen behave normal and the Kuhn–Mark–Houwink relation reads log ([η]/mL g −1 ) = −1.185 + 0.735 log M . Possible reasons for the dissimilarities of the behavior of cellulose in these two solvents are being discussed. The comparison of three different methods for the determination of [η] from viscosity measurements at different polymer concentrations, c , demonstrates the advantages of plotting the natural logarithm of the relative viscosities as a function of c . © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011