Physical structure and thermal behavior of ethylcellulose
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The physical structure and properties of ethylcellulose (EC) powders of different molecular weights were examined. A molecular weight in the range of 20–144 kDa with a large polydispersity was determined. EC thermal analysis revealed a glass transition at ~130 °C and a melting temperature at ~180 °C. Glass transition temperatures increased with polymer molecular weight. Wide angle (WAXS) analysis detected an amorphous broad peak at q = 1.5 Å−1 and a distinct Bragg’s peak at 12.6 Å, which seems to be related to a supramolecular ordered structure of the polymer. These observations were confirmed using high temperature powder X-ray diffraction analysis where the crystalline peak disappeared above the melting temperature of the polymer. Ultra-small angle (USAXS) results were fitted to the Bouacage fractal unified model and fractals with an average size of 100–600 nm with a relatively smooth surface were predicted. This prediction was confirmed by transmission electron microscopy (TEM) images. According to our results, the EC polymer has a semi-crystalline structure, with crystalline domains within an amorphous background.
KeywordsEthyl cellulose Semi-crystalline Powder Fractal X-ray scattering
Research supported by the Ontario Ministry of Agriculture and Food (OMAF) and the Natural Sciences and Engineering Research Council of Canada (NSERC). We acknowledge the technical assistance of Fernanda Peyronel for setting up experiments and data analysis. The author wish to thank Dr. Jan Ilavsky from the APS sector 15ID-D USAXS/SAXS facility for his help conducting both SAXS and USAXS experiments. ChemMatCARS Sector 15 is principally supported by the National Science Foundation/Department of Energy under grant number NSF/CHE-0822838. Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
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