Determination of glass transitions in novel cellulose polymers by synchrotron wide-angle X-ray scattering

Cellulose as a Source of Water Dispersible Renewable Film-Forming Materials

“…Clearly, the T g of the product decreased with increasing chain length of the alkanoyl side chain (Table , entries 2–6) but then began to rise again (Table , entry 7). This finding is consistent with prior results, in which there is a decrease in T g as the chain length of the substituent increased in monosubstituted or per-esterified CEs up to C 6 /C 8 , after which the T g increased. , There is some evidence that larger fatty acid moieties display independent chain-melt characteristics segregated from the cellulose backbone …”

“…Catalyst loading could be reduced 40-fold which is a remarkably low acid catalyst level for this transformation; compared to a sulfuric acid catalyzed reaction this is particularly time-efficient (Table , entries 2–4). The lower catalyst levels required longer reaction times and produced lower M W cellulose ester products but with the desirable (for our application) characteristic of depressed T g values . In an interesting outcome, reactions performed at elevated reaction temperatures with these low catalyst loadings again produced very low color and low M W products, and with substantially reduced T g values (Table , entry 5).…”

“…The lower catalyst levels required longer reaction times and produced lower M W cellulose ester products but with the desirable (for our application) characteristic of depressed T g values. 26 In an interesting outcome, reactions performed at elevated reaction temperatures with these low catalyst loadings again produced very low color and low M W products, and with substantially reduced T g values (Table 4, entry 5). It is likely that the catalyst was behaving as a Lewis acid−assisted Brønsted acid, a feature of Al(OTf) 3 we have investigated and discussed over a period of time.…”

“…24,25 There is some evidence that larger fatty acid moieties display independent chain-melt characteristics segregated from the cellulose backbone. 26 Figure 1 shows a BLAC species with low levulinoyl content as compared to a LAC of high DS Lev . Apart from the selfevident substituent contributions to the 1 H NMR spectrum (δ < 3.0 ppm), it is notable in the spectra that the incorporation of the levulinoyl ester generates a significantly greater range of chemical-shift environments for the cellulosic methines as evidenced by the complexity of the region δ 3.4−5.4 ppm.…”