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

Synchrotron wide angle X-ray scattering (WAXS) was used to measure the glass-transition temperature (Tg) values for various cellulosic materials including a novel cellulose ester. WAXS patterns were obtained of films cast on silicon nitride windows. Two strong scattering peaks were observed that correlated with the intramolecular repeating anhydroglucose unit (d = 10.6–14.3 Å) and an intermolecular packing spacing (d = 4.4–4.5 Å). Real-time measurements were made during temperature cycling over a range of 80–160 °C at 5 °C/min. Significant shifts in position, width and area for the peak assigned to the intermolecular arrangement of the pseudo-linear cellulose mixed-ester chains were correlated with temperature. The calculated Tg mid-points correlated well with Tg values determined by differential scanning calorimetry (DSC). This application of temperature-dependent WAXS measurements shows promise for Tg determination in samples where shallow second-order transitions are observed by DSC and where other techniques are not applicable.

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