Abstract: | Potato starch phosphate (PSP) particles were synthesized via an esterification process of potato starch with a mixture of various concentrations of phosphoric acid and urea. The electrorheological (ER) characteristics of the synthesized PSP particles, suspended in a silicone oil, were examined. The PSP granule‐based ER fluid exhibited typical ER behavior, possessing a nonvanishing yield stress under an applied electric field. Enhanced polarization and higher yield stresses were observed as the content of phosphate groups in the starch increases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1770–1773, 2004 |