Cellulose carbanilate

The final section addresses degradation and oxidation reactions in a commonly used derivatization system for cellulose, a mixture of DMSO and phenyl isocyanate to achieve cellulose carbanilation, e.g. for analytical purposes. Mechanistic studies were aimed at verifying the assumed oxidative action of this reaction system, and trapping methodology was employed to detect responsible intermediates. 

Indeed, the oxidizing effect of a DMSO/PhNCO mixture under standard cellulose carbanilation conditions, i.e. reaction times of 2-3 d at tem-... 

Scheme 25 Generation of methylsulfonium ylides in DMSO-based cellulose carbanilation mixtures, trapping by 3,4-dehydro-a-tocopheryl acetate (67), and quick color testing for their presence by naphthoquinone derivative 69...

The oxidative effect of the DMSO/PhNCO system on cellulose was confirmed by means of alcoholic model compounds (60, 62, 64) that were neatly oxidized into the corresponding ketones. The presence of the active species, the oxidatively acting sulfonium ylide 66, in the cellulose carbanilation mixture was proven by trapping with two reagents, a tocopherol-based compound (48) and a naphthoquinone (68) that was also used in a facile color test to estimate the degrading effect of certain carbanilation mixtures and conditions on cellulose. 

Fig. 5. Sedimentation coefficient (s] vs. molecular weight M for cellulose esters 1 cellulose carbanilate in ethyl acetate 2 cellulose butyrate in methyl ethyl ketone ) 3 cellulose mono-phenylacetate in benzene 4 cellulose diphenyl phosphonocarbamate in dioxane ) 5 cellulose benzoate in dioxane ...

Fig. 24. A ([n]/[tj])/([n]/[T)l) vs. x plot at various A/d parameter values. Curve 1 according to Eq, (59) at px = > and A/d = curves 2-5 according to the Noda-Hearst theory with additional factor bo according to Eq. (64) at d/A = 0 (2) 0.25 (3) 0.5 (4) 1 (5). Points designate experimental data cellulose carbanilate in dioxane ) ( ) ladder polydichlorophenylsiloxane in bromoform (o) and in tetrabromoethane...

The points in Fig. 24 represent the experimental values of A for a ladder poly-dichlorophenylsfloxane and cellulose carbanilate For both polymers the experimental data are in agreement with theoretical Curve 4 corresponding to the value of d/A = 0.5 for a kinetically flexible chain polymer. This qualitatively demonstrates that the hydrodynamic properties of the molecules of these two polymers at low X differ from those of an infinitely thin worm-like model. However, to obtain quantitative agreement between theory and experimental data according to Curve 4 in Fig. 24, A/d should be equal to 2 — a reasonable value for many flexible-chain polymers not realistic for such r d-chain polymers as ladder polysiloxanes or cellulose ethers and esters. 

Fig. 28. Plot of G (Eq. (62)) vs. reduced chain length x = 2 L/A for fractions of ladder polydichloro-phenylsiloxane in tetrabromoethane (1), bromoform (2), and benzene (3) and cellulose carbanilate in dioxane (4) Theoretical curves are plotted according to Ref. at the following values of polydispersity parameter U = U = 1 (I), 1.4 (II), 1.6 (III), 1.8 (IV)...

Simibr dependences of (x/g) on c for solutions of cellulose carbanilate fractions in diox-ane are shown in Fig. 27. 

The dependence of G for fractions of cellulose carbanilate and ladder polydichlorophenyl-siloxane on chain length x is described in Ffe. 28. Curve I illustrates the Noda-Hearst theoretical dependence ... 

Fig. 32. Temperature dependence of [t]) and ln)/lr l for solutions of cellulose carbanilate in dioxane )...

As an example of the use of Eq. (28) (p. 114), the data for fractions of cellulose carbanilate, the molecule of which can be represented by a partially drained worm-like coil, are plotted in Fig. 64. The dependence of the expression of the left-hand side of Eq. (28) on is approximated by a straight line the slope of whidi yields the length of the Kuhn segment A and the intercept the hydrodynamic diameter of the chain d. The curves in Fig. 64 provide the values of A = 160 A and d = 6 A for the cellulose carbanUate chain. 

F%. 68. C vs. M plot of cellulose carbanilate samjdes in dioxane. Broken lines correspond to the tlworetical values of C 1 rigid to4 2 rigid coil, 3 rigid sphere, 4 first mode, 5 second mode, 6 third nwde... 

The experimental dispersion curves which are similar to those in Fig. 66 yields the values of cellulose carbanilate versus molecular weight M (Fig. 71). The general character of experimental curves corresponds to the theoretical dependence depicted in Eq. (86 ). This permits the determination of the dipole moment of the monomer unit, mq. fto the initial slopes (mq/Mq) and the calculation of the parameter of chain rigidity S from their limit (mq/M) S. 

Fig. 77. K vs. M plot of cellulose carbanilate fractions in dioxane (points = experimental data 217) Qjj yg Curves characterize theoretical dependences of K/Koo on x at various values of d shown here and the values Aa, S and mo (Table 14)...

Fig. 16 Optical properties of different lyotropic cholesteric phases of cellulose carbanilates,...

The presence of a cholesteric helicoid stracture determines the significant optical rotation of HPC in aqueous solutions p is 4 10 degml/dm-g [10]. Analysis of the optical properties indicates the formation of a left-handed cholesteric helix in aqueous solutions of HPC, solutions of cellulose carbanilate in methyl ethyl ketone, and ethylcellulose in dichloroacetic acid. In most cases. 

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