An osmometric study of the thermodynamic properties of cellulose triacetate solutions.

General properties of dilute polymer solutions were considered with particular emphasis on solvation. Current theories of polymar-solvent interaction were outlined. Fibrous cellulose triacetate was prepared from cotton cellulose by a heterogeneous acetylation method. The polymer was characterised and analysed for full acetylation. Mine solvents were chosen to investigate the solution properties of cellulose triacetate. These were : chloroform,methylene chloride, tetrachloroethane,formic acid,ocstic acid,dichloroacetic acid,meta-cresol,ortho-chlorophenol and dimethyl sulphoxide. The solvents were purified and their densities determined over the temperature range 10-40 C. The measurement of osmotic pressure of cellulose triacetate in six solvents,over the temperature range 10-40C,was described in detail,and useful information regarding membrane behaviour was obtained. Values of the polymer-solvent interaction parameter chi[1] and of the free energy of dilution DeltaG[1] were calculated from measureent of the static osmotic head at several temperatures. The enthalpy DeltaH[1] and entropy DeltaS[1] of dilution were computed from the temperature coefficient of DeltaG[1]. Enthalpies and entropios of dilution were generally positive end constant over the temperature range studied. Entropies of dilution ware smaller than those obtained with more flexible polymers,but greater than ideal values. Values of DeltaH[1], DeltaS[1] and of chi[1] were interpreted in terms of solvation,and attempts were made to apply current theories of polymer-solvent interaction. Results seemed capable of partial interpretation in terms of simpler lattice theories providing certain properties of the system are taken into account. Viscosities of dilute solutions of cellulose triacetate in the nine solvents were studied. Viscosities were found to decrease with temperature in all cases,although a linear dependence of the limiting viscosity number on temperature was not observed. There was no correlation between the limiting viscosity number or the Huggins' constant and solvent power. Application of hydrodynamic theories was more successful,and useful measures of solvent power were thus obtained. The quantitative solubility of cellulose triacetate in the nine solvents was determined at 25 °C ,and solubility results were interpreted, along with other parameters of solvent power, in terms of the varying degrees of solvation resulting from hydrogen bonding between active hydrogens of the solvents and the acetyl groups of cellulose triacetate