Comparative study of the hydrodynamic properties of cellulose and amylose tricarbanilates in dilute solutions viscosity, sedimentation and diffusion measurements in 1,4‐dioxane in the molecular weight range of 500 ≤<i>M</i>≤ 5·10⁶

Abstract

Abstract Comparative hydrodynamic measurements were performed for cellulose tricarbanilates (CTC) and amylose tricarbanilates (ATC)—covering the whole region from the monomer up to the highest available molecular weight of 3,6 . 10 6 . The intrinsic viscosity vs. molecular weight relationships exhibit in both cases characteristic S‐shaped curves. In the region of oligomers the intrinsic viscosities remain almost constant; it follows then a steep increase with molecular weight which finally flattens out to constant slopes for high molecular weights. In the high molecular weight region the curves may be approximated by Kuhn‐Mark‐Houwink equations with exponents of 0,90 and 0,88 for CTC and ATC, respectively. The intrinsic viscosities are by a factor two smaller for ATC than for CTC. The S‐shaped curves are interpreted as a result of the finite cross‐section of the chains and a certain chain stiffness. Stockmayer‐Fixman plots gave strongly bent curves which is shown to be due to chain rigidity. Sedimentation coefficients and diffusion constants as functions of the molecular weight approach straight lines in a double logarithmic plot for large molecular weights; for shorter chains characteristically bent curves are obtained which are ascribed to chain stiffness and finite chain cross‐section. The origin of chain stiffness in CTC is discussed to be due to H‐bond formation between the NH‐group of the substituent in C 2 position of the sugar ring and a CO‐group of the substituent in C 6 of a neighbouring repeating unit. This interpretation is supported by the low viscosity of mannan tricarbanilate (MTC), in which the facility of H‐bond formation is lost and higher flexibility is obtained.