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The propanoate of (2-hydroxypropyl)cellulose was prepared by esterification of (hydroxypropyl) cellulose. Thin layers of the bulk polymer between glass surfaces were colored at room temperature, due to cholesteric reflection from a liquid crystalline structure. On heating, the color moved to longer wavelengths and disappeared; the liquid crystalline-isotropic transition was complete at 167 °C. The polymer also forms a lyotropic mesophase in acetone at concentrations above ~30 wt % polymer.

Acetoxypropyl)cellulose (APC) fractions form thermotropic mesophases and also form lyotropic mesophases in dibutyl phthalate (DBP). The liquid crystal to isotropic transitions of these mesophases are examined. The critical concentration for mesophase formation, 0\ increases markedly with temperature. This increase is caused primarily by the reduced stiffness of the chain; as calculated in the preceding paper, the axial ratio of the Kuhn segment decreases from 10.8 to 5.6 ± 0.4 in the temperature range from 25 to 150 °C. At room temperature, the volume fraction of APC in DBP needed for anisotropic phase separation is 0.52 ± 0.02, for chains with contour lengths from 102 to 103 nm. The ordered phase coexists with a more dilute isotropic phase up to a polymer volume fraction of 0.69 ± 0.04. The concentrations of both phases increase with that of the solution. The molar mass of the APC in the mesophase exceeds that in the isotropic phase. The enthalpy of the transition to an isotropic solution, measured by differential scanning calorimetry, decreases with a reduction in the APC concentration. The experimental results are interpreted in the light of recent theories for liquid crystalline phase separation. Theories introducing orientational anisotropic interactions between chains are used to explain the extended temperature or concentration range of the thermotropic and lyotropic APC mesophases. However, the variation in critical concentration can be roughly predicted over a very wide temperature range from the freely jointed segment model without anisotropic interactions.

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A thermotropic cholesteric polymer, (acetoxypropyl)cellulose (APC), is prepared from (hydroxypropyl)cellulose and acetic anhydride. The unit ether and unit ester contents per anhydroglucose unit, determined by chromic acid oxidation and saponification, are 3.1 ± 0.3 and 1.9 • 0.1, respectively. Fractions ranging in molar mass from 2.2 X 104 to 6.5 X 105 daltons, and of the same chemical composition as the unfractionated polymer, are obtained by fractional precipitation with re-heptane. The limiting viscosity numbers of APC and fractions are measured in dimethyl phthalate at 25, 105, and 150 °C. The exponent in the Mark-Houwink-Sakurada relationship decreases from 0.88 ± 0.05 at 25 °C to 0.57 ± 0.05 at 150 °C, reflecting the gradually increasing flexibility of the molecular chain. The chain conformation parameters (equivalent Kuhn segment length, diameter, and mass per unit length) are calculated from the viscosity data by means