Synthesis, Characterization, and Gas Permeation Properties

t-Butylcarbamates of Cellulose Derivatives
wavenumber range. Moreover, the absence of the peak around 2270–2100 cm -1 ,
assignable to the isocyanate group of the starting material, provided a clear evidence of
the product purification.
Figure 3. FTIR spectra of 1, 2, 1a, and 2a.
The molecular weights of the starting as well as the derivatized polymers were
determined by the gel permeation chromatography and the data are summarized in
Table 1. The molecular weight determination of ethyl cellulose (1; DSEt, 2.69 and 2;
DSEt, 2.50), cellulose acetate (3; DSAc, 2.46), and their carbamate derivatives (1a–3a)
was carried out by making use of THF as eluent while for 4 and 4a, elution was
effected with LiBr solution (10 mM) in DMF because of the insolubility of cellulose
acetate (4; DSAc, 1.80) in THF. The carbamoylation of cellulose derivatives
accompanied an increase in the molecular weight of the polymers, e.g., the Mn of 3 and
4 were observed to be 64 000 and 89 000 while those for 3a and 4a were 70 000 and
93 000, respectively. Moreover, the polydispersity indices (Mw/Mn) of the carbamate
derivatives (1a–4a) were not quite different from those of 1–4, for instance, the Mw/Mn
of 2 and 2a were 2.6 and 2.4 and for 3 and 3a were 2.3 and 2.2, respectively, thus
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