Preparation and property of model homogeneous ER fluids having urethane groups

Urethane modified polyether liquids composed of hard and soft segments exhi bit either positive or negative ER effect depending on the structure. Here some model compounds of the urethane polymers were synthesized, and the inf luence of chemical structure, e.g. displacement of hard and soft segments a nd existence of branches, on the ER effect was studied. It was found that n egative ER effect is enhanced by introducing a branched structure in the po lyether main-chain or a hard segment at center of the linear polyether.