Synthesis, Characterization, and Gas Permeation Properties

t-Butylcarbamates of Cellulose Derivatives
with increasing critical volume of gases whereas the S value experiences an increase
with increasing critical temperature of gases. 1a Similar tendencies were observed in
the D and S values of the polymer membranes of the starting (1–4) as well as the
carbamoylated cellulose derivatives (1a–4a); e.g., in the case of 4a, the diffusivity of
CH4 was the lowest and that of O2 was the highest (0.65 and 4.09 10 7 cm 2 s -1 ,
respectively) while CO2 displayed the highest solubility and N2 the lowest (37.5 and
0.72 10 3 cm 3 (STP) cm -3 cmHg -1 , respectively). The diffusion coefficients of these
carbamate-functionalized cellulosics (1a–4a) were in the order DO2 > DN2 > DCO2 >
DCH4, the same as for the starting polymers, ethyl cellulose and cellulose acetate.
Similarly, the S values of 1–4 and 1a–4a were observed to follow the same trend (SCO2
> SCH4 > SO2 > SN2).
Figure 10. Plot of SCO2 vs DCO2 for polymers 2, 4, 2a, and 4a.
It is noteworthy that the increase in the diffusion coefficients upon
carbamoylation was more pronounced than the decrease in the solubility coefficients,
thus leading to the net effect of enhanced permeability. Furthermore, these results
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