Solutions of cellulose derivatives

Formerly it was believed that in their physical properties, as for instance no increase in boiling point and in osmotic pressure, colloidal solutions of cellulose derivatives were radically different from solutions of crystalline substances having small molecules. Now, however it is clear that the difference is not so considerable and that a close analogy exists between solutions of cellulose and its derivatives and those of substances of low molecular weight. 

One of the arguments against the existence of micelles in solutions of cellulose derivatives is the fact that when cellulose is converted into its derivative, e.g. an ester, the degree of polymerization remains almost unchanged. This however only occurs when ester fonnation is carried out under strictly controlled conditions (nitration at low temperature with nitric and phosphoric acids mixture — p. 341, or with nitric, acetic acids and acetic anhydride mixtures — p. 344). The relevent data found by Staudinger and Mohr [32] are collected in Table 40. 

Solutions of cellulose derivatives, such as nitrocellulose, passed through a fine porous filter demonstrate neither the Tyndall effect, nor the presence of particles visible in the ultra-microscope. This is one more piece of evidence that the properties of these solutions are the same as those of substances with low molecular weight. The same holds for cellulose in ammoniacal solutions of cupric oxide ( cupr-ammonium ). 

Fig. 42, Correlation between solvation and some characteristic features of solutions of cellulose derivatives...

The characteristic features of dilute solutions of cellulose derivatives can be reasonably and consistently explained by solvation (Fig. 42). 

Alumina samples for investigation were prepared from aluminum hydroxide (Condea, type DISPERAL). A batch of aluminum hydroxide was kneaded either with water dematerialized solution of HNO3 (1%) or with water solution of cellulose derived product (commercial name CULMINAL), extruded with using of piston extruder, dried for 24 h at room temperature, then for 24 at 110 C and calcined for 4 h at 550, 650, 750, 800 or 850 "C). Obtained samples of alumina extrudates are described as DN (aluminum hydroxide "Disperal"... 

Table 3. Incipience of Cholesteric Phase Separation from Solutions of Cellulose Derivatives...

Ethylhydroxyethylcellulose is an ether of cellulose with both ethyl and hydroxyethyl substituents attached via ether linkages to the anhydroglucose rings. It swells in water to form a clear viscous colloidal solution. Preparation of solutions of cellulose derivatives requires hydration of the macromolecules, the rate of which is a function of both temperature and pH, as shown in the example in Fig. 8.f8. 

Liquid crystalline (LC) solutions of cellulose derivatives form chiral nematic (cholesteric) phases. Chiral nematic phases are formed when optically active molecules are incorporated into the nematic state. A fingerprint texture is generally observed under crossed polarizers for chiral nematic liquid crystals when the axis of the helicoidal structure is perpendicular to the incident light (Fig. 2). 

Sixou, P. Bosch, A.T. Lyotropic liquid crystal solutions of cellulose derivatives. In Cellulose Structure, Modification and Hydrolysis Young, R.A., Rowell, R.M., Eds. Wiley New York, 1986 205-219. 

VSH Vshivkov, S.A. and Rusinova, E.V., Effect of magnetic field on phase transitions in solutions of cellulose derivatives, Polym. Sci., Ser. A, 50, 725,2008. 

A variety of phase diagrams appear depending on their relative strengths, some of which correspond to the actually observed phase diagrams of the solutions of cellulose derivatives. 

BAB Baba, Y. and Kagemoto, A., Phase diagrams of aqueous solutions of cellulose derivatives (Jap.), Kobunshi Ronbunshu, 31, 446, 1974. 

V. G. Kulichikhin, V. V. Makarova, M. Yu. Tolstykh, and G. B. Vasil ev, Phase equilibria in solutions of cellulose derivatives and the rheological properties of solutions in various phase states Polym. Sci. Series A 52,1196-1208 (2010). 

J. Bheda, J. F. Fellers, and J. L. White, Phase behavior and structure of hquid crystalline solutions of cellulose derivatives. Colloid Polym. Sci. 258, 1335-1342 (1980). 

MOO Moore, W.R. and Tidswell, B.M., Thermo namic properties of solutions of cellulose derivatives. 1. Dilute solutions of secondary cellulose acetate, /. Polym. Sci., 27,459,1958. 

Bheda J, Fellers J, White J (1980) Phase behavior and structure of liquid crystalline solutions of cellulose derivatives. Colloid Polym Sci 258 1335-1342 Butt H-J, Graf K, Kappl M (2003) Physics and chemistry of interfaces. Wiley, Weinheim Canejo J, Godinho M (2013) Cellulose perversions. Materials 6 1377-1390 Canejo JP, Borges JP, Godinho MH, Brogueira P, Teixeira PIC, Terentjev EM (2008) Helical twisting of electrospun liquid crystalline cellulose micro- and nanofibers. Adv Mater 20 4821- 825... 

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