In this study, poly(2-hydroxyethly methacrylate), poly(hema), was synthesized by free radical polymerization using K2S2O8 as an initiator. The polymer was characterized by FTIR, H-1 NMR and elemental analysis measurements. The molecular mass of poly(hema) was determined by osmometry, viscometry and end group analysis techniques approximately as 6 x 10(3) g/mol. Poly(hema) was partially hydrolyzed and converted to a lithium salt, poly(Li-hema) before the electrorheological (ER) measurements carried out. A series of particle size of poly(Li-hema) polymeric salt were prepared and average particle diameters were determined by dynamic light scattering (DLS) as 8, 13, 19 and 25 mu m. Suspensions of poly(Li-hema) polymeric salts were prepared in four insulating oils namely silicone oil (SO), mineral oil (MO), dioctylphthalete (DOP) and trioctyltrimellitate (TOTM). ER properties of poly(Li-hema)/silicone oil suspensions were Studied as a function of electric field strength, particle size, dispersed phase concentration, shear rate, shear stress, temperature, frequency and promoter. For these ER suspensions, yield stresses and excess shear stresses were determined. Further dielectric properties of poly(Li-hema) ionomer were also investigated. (c) 2005 Elsevier B.V. All rights reserved.