A series of random co-poly(ionic liquid)s (co-PILs) neutralized with mixed counterions of organic bis(trifluoromethane sulfonyl)imide ([TFSI]) and inorganic tetrafluoroborate ([BF₄]) of different mole ratio had been synthesized for use as electrorheological (ER) particles. The temperature-modulated ER effect of the co-PIL particles had been investigated and compared with that of homo-poly(ionic liquid)s neutralized with single organic [TFSI] counteranions. This work demonstrated that the ER effectiveness and temperature effect of electrorheological fluid based on neat organic counteranions-typed PILs can be significantly improved by a simple substitution of inorganic counteranions with a suitable mole ratio. The higher electrorheological effectiveness with sup-pressed leakage current density and enhanced temperature stability originated from that the substitution of inorganic counteranions for organic counteranions could systematically elevate the glass transition temperature and modulate the activation energy of ion movement in PILs matrix.

Electrorheology,Co-poly(ionic liquid)s,Temperature effects