A reversibly electro-controllable polymer brush for electro-switchable friction

We report electrically switchable friction, which is reversibly manipulated by an external electric field via an electro-controllable polymer branched brush. The electro-controllable polymer branched brush, poly-sodium allyloxy hydroxypropyl sulfonate (poly-AHPS), was grafted onto an electrically conductive indium tin oxide (ITO) glass, and it demonstrated the capability of switching states by responding to the external electric field in a controllable manner. The two states of poly-AHPS branched brushes -stretched polymer brush arrays when negatively charged and rolled polymer knolls when positively charged -correspond to two different friction factors. Meanwhile, the shifting span for friction factors would be compressed by sandwiching a polar molecule medium or a nonpolar molecule medium, and exhibited a medium-controllable character. The proposed electric-field-responsive polymer brush is expected to be a manoeuvrable matrix for automatic control of friction, and to find wide application in automatization, intelligent manipulation and actuators.