Cellulose tributyrate

Taking the length per repeat unit (i.e., bond angles already considered) as 0.78 nm in each instance, evaluate the factors (1 + cos 0)/(l - cos (p) and cos (p for each polymer. Ignoring the difference between 130 and 140°C, do you find the difference in steric hindrance between the tributyrate and tri-caprylate to be what you expected Is the effect of temperature on the 1q value of cellulose tributyrate what you expected Briefly explain each answer. For each polymer, calculate r if n = 10 also do this for the hypothetical chain with no restrictions to rotation and having the same repeat length. 

Table 9. and Nmr Chemical Shifts, ppm, and Coupling Constants, for Cellulose Triacetate, Cellulose Tripropionate, and Cellulose Tributyrate ... 

Fig. 131.—The reciprocal melting point plotted against the volume fraction of diluent for cellulose tributyrate in benzo-phenone ( ), in hydroquinone monomethyl ether (O), and in ethyl laurate (A). (Mandelkern and Flory. )...

According to Eq. (29), the initial slope of a plot of 1/Tm against the diluent concentration Vi should be inversely proportional to the heat of fusion AHu , such curvature as may occur should be indicative of the magnitude of %i- Results for cellulose tributyrate are plotted... 

Once 1 has been determined, the values of the other two parameters are more readily deduced by plotting the quantity (1/Tm — l/Jm)/vi against vi. Or, considering %i to he inversely proportional to the temperature and recalling Eq. (XII-21 ), we may plot this quantity against vi/Tm Results for cellulose tributyrate in three diluents are treated in this manner in Fig. 132. According to Eq. (29), the intercepts should equal (i2/AJT ) (Vw/vi), and the energy of interaction B = xiR T/vi... 

Table XXXIV.—Heats of Fusion and Energy of Interaction Constants as Obtained from Melting Point Measurements on Mixtures of Cellulose Tributyrate with Diluents s...

This assumption is based on the fact that the polymer-solvent interaction parameter [see Eq. (8)] of the tributyrin-cellulose tributyrate system, as evaluated from melting-point depressions, is nearly zero at about 100° C [Mandelkern and Flory (160)]. It does not follow, however, that the system is athermal, for the parameter generally involves an entropy contribution. Furthermore, the heat and entropy parts of this parameter vary with the concentration in a complicated way, especially in polar systems [see, for example, Takenaka (243) Zimm (22) Kurata (154)]. Thus it is extremely hazardous to predict dilute solution properties from concentrated solution properties such as the melting-point depression, at least on a highly quantitative level as in the present problem. 

The Mandelkern-Flory viscosity data for cellulose tributyrate are plotted according to Eq. (58) in Fig. 18. It is seen that the line for the viscosities in the good solvent methyl ethyl ketone at 30° C passes without strain to the same intercept as the lines for the two high-temperature theta solvents. The intercept gives K = (9.7 1.5) 10-4 and a = 1.79 0.10, as listed in Table 9. Although, as discussed in the... 

Fig. 18. Main figure viscosity plot for cellulose tributyrate- Insert interaction parameter B for cellulose...

There is no line for tributyrin-cellulose tributyrate in Fig. 18, because the viscosity measurements were limited to only one sample. However, if we assume that K maintains at all temperatures the value derived above from data in other solvents, the interaction parameter B may be evaluated from Eq. (58) at each temperature. The result of this calculation is shown in the insert to Fig. 18, which demonstrates that the linear... 

Solvents — For cellulose tributyrate Benzene, chloroform, cyclohexanone, dodecane/ tetralin (3 1, >130°C), tetrachloroethane, xylene (hot) (4,5)... 

Degree of crystallinity of cellulose tributyrate (%) Annealing temp. (K) Annealing hours (8)... 

Cellulose tributyrate has a lower melting point than CTA or the triproprionate and, as might be expected due to the plasticizing effect of the butyrate groups, is softer than these esters. However, it has not been made on a commercial scale. See Table II for properties of cellulose tributyrate. 

Diluted Systems Cellulose tributyrate in dimethyl phthalate ... 

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