AbstractThirteen kinds of cellulose acylates from the acetate to stearate were prepared by trifluoro acetic anhydride–fatty acid esterification, and their dielectric constant and loss were measured over wide temperature and frequency ranges. Two types of relaxation process (αdand βd) were recognized for all the acylates and an additional relaxation process (γd) was detected for the acylates with side chain length longer than that of the butyrate. These αdto γdprocesses were attributed to the micro‐Brownian motion of the main chain (αd), the motion of oxycarbonyl group of the side chain (βd) and the motion initiated by minimum three methylene groups in addition to the oxycarbonyl group (γd), respectively. In the transition map for the βdprocess, inflection points were observed, and the temperature at the inflection point could be regarded as a freezing point of the micro‐Brownian motion of the acyl side chain. In the temperature region above the inflection point, plots in transition map for all the acylates were found to be on the same
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