Portal de Periódicos da CAPES

Thermodynamic properties of solutions of cellulose derivatives. I. Dilute solutions of secondary cellulose acetate

1958; Wiley; Volume: 27; Issue: 115 Linguagem: Inglês

10.1002/pol.1958.1202711535

1542-6238

W. R. Moore, B. M. Tidswell,

Material Dynamics and Properties

Abstract Osmotic pressure of dilute solutions ( c ≤1.0 g./100 ml.) of a fraction from a secondary cellulose acetate in representative solvents have been measured at two or three temperatures. Number‐average molecular weights in acetone, aniline, methyl acetate, and pyridine do not vary with temperature but are significantly higher in methyl acetate in which association of polymer is possible. Molecular weights in acetic acid, nitromethane, and dioxane decrease with increase of temperature presumably because of degradation. Values of Δ F 1 , Δ H 1 , and Δ S 1 have been estimated from temperature coefficients of osmotic pressure. All the systems are endothermal. It is suggested that the polymer is fully solvated and that solvated polymer and solvent mix with absorption of heat. With the exception of the aniline system, values for which are high, values of Δ H 1 appear to be in the order to be expected from the solubility parameters of solvent and solvated polymer. Δ H 1 and Δ S 1 decrease with increase of temperature in all cases except that of acetic acid. Δ H 1 /ϕ , where ϕ 2 is the volume fraction of polymer, seems to be effectively constant at each temperature. Values of Δ S 1 are greater than “ideal” values but are less than those obtained for comparable systems containing more flexible and less polar polymers. Δ S 1 /ϕ decreases with increase of concentration but in some cases there is an increase at the highest concentration. Δ F 1 becomes more negative with increase of temperature. It would seem that both entropy and heat terms contribute to the value of the interaction parameter χ 1 . It is possible, if solvation and the segment size and stiffness of chains are taken into account, that approximate lattice theories may apply to solutions of cellulose derivatives at lower concentrations than in cases of more flexible and less polar polymers.