Viscosity-Molecular Weight Relationship for Cellulose Solutions in Either NMMO Monohydrate or Cuen

The intrinsic viscosities, [eta], of nine cellulose samples, with molar masses from 50 x 10(3) to 1 390 x 10(3) were determined in the solvents NMMO*H(2)O (N-methyl morpholin N-oxide hydrate) at 80 degrees C and in cuen (copper II-ethlenediamine) at 25 degrees 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 [eta]/M relation reads log ([g]/mL g(-1)) = -1.465 + 0.735 log M. Beyond that molar mass [eta] remains almost constant up to M approximate to 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 ([eta]/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 [eta] 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. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 670-676, 2011