Cellulose tricarbanilate, formation

Following the first observation of mesophase formation of HPC/H2O, the rheology of this system has been widely investigated. Rheological studies of other cellulosic mesophases, e.g., cellulose, ethylcellulose, and cellulose tricarbanilate, have also been reported. 

Many cellulose derivatives form lyotropic liquid crystals in suitable solvents and several thermotropic cellulose derivatives have been reported (1-3) Cellulosic liquid crystalline systems reported prior to early 1982 have been tabulated (1). Since then, some new substituted cellulosic derivatives which form thermotropic cholesteric phases have been prepared (4), and much effort has been devoted to investigating the previously-reported systems. Anisotropic solutions of cellulose acetate and triacetate in tri-fluoroacetic acid have attracted the attention of several groups. Chiroptical properties (5,6), refractive index (7), phase boundaries (8), nuclear magnetic resonance spectra (9,10) and differential scanning calorimetry (11,12) have been reported for this system. However, trifluoroacetic acid causes degradation of cellulosic polymers this calls into question some of the physical measurements on these mesophases, because time is required for the mesophase solutions to achieve their equilibrium order. Mixtures of trifluoroacetic acid with chlorinated solvents have been employed to minimize this problem (13), and anisotropic solutions of cellulose acetate and triacetate in other solvents have been examined (14,15). The mesophase formed by (hydroxypropyl)cellulose (HPC) in water (16) is stable and easy to handle, and has thus attracted further attention (10,11,17-19), as has the thermotropic mesophase of HPC (20). Detailed studies of mesophase formation and chain rigidity for HPC in dimethyl acetamide (21) and for the benzoic acid ester of HPC in acetone and benzene (22) have been published. Anisotropic solutions of methylol cellulose in dimethyl sulfoxide (23) and of cellulose in dimethyl acetamide/ LiCl (24) were reported. Cellulose tricarbanilate in methyl ethyl ketone forms a liquid crystalline solution (25) with optical properties which are quite distinct from those of previously reported cholesteric cellulosic mesophases (26). 

One indication that the formation of the trinitrate derivative of cellulose causes depolymerization and the formation of the tricarbanilate does not is that the DPs of cellulose determined as the tricarbanilate are considerably greater than those obtained as the trinitrate (22). Although a plausible explanation for this difference is the depolymerization of cellulose curing formation of the trinitrate derivative, comparison of DP derived from the trinitrate and the tricarbanilate using the same sources of cellulose indicates that this difference may simply be a result of errors in the Mark-Houwink coefficients for cellulose trinitrate in acetone solution (22). 

The major advantage of using cadoxen solutions of cellulose for SEC is that the cellulose need not be derivatized before determination of the SEC. This eliminates the time-consuming step of derivative formation, which in the case of the tricarbanilate derivative requires more than 48 h. In addition, smaller cellulose samples are required and any changes in the cellulose resulting from sample preparation are minimized. 

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