DIRECT SYNTHESIS OF ELECTRORHEOLOGICAL SUSPENSION CONTAINING SALT OF POLY(METHACRYLIC ACID) AND ITS ELECTRORHEOLOGICAL EFFECT

Colloidal suspensions containing salts of poly(methacrylic acid) which exhibit high electrorheological (ER) activity were synthesized by inv erse emulsion polymerization. Factors influencing the ER effect were s tudied. The results showed that maximum yield stress occurred at optim um amounts of both polymeric stabilizer and crosslinking agent used in the inverse emulsion polymerization as well as a certain water conten t of the particles, while yield stress increased with electric field s trength, average diameter of the particles below 0.9 mu m, or the mola r ratio of the salt to the acid. The ER activity for the suspensions c ontaining different monovalent counter ions decreased in the following order: Li+ > Na+ > K+ > NH4+. The phenomena were discussed with the i onic polarization mechanism. (C) 1995 John Wiley & Sons, Inc.