Charge-induced local dewetting on polymer electrets studied by atomic force microscopy.

Polymer electrets are one of the most important series of electrets, which are widely used both in academic research and industrial applications. The effect of trapped charges on dielectric properties of the polymer electret is critical for more intelligent utilization of these materials. Herein we report the charge-induced polymer relaxation reflected by the local dewetting of the polymer electrets with charge patterns. Because the difference in charge-induced relaxation results in selective dewetting of thin polymer films, polymers in the charged areas are preferentially dewetted from the substrate compared with the neutral areas under heating or solvent annealing, leading to the appearance of hole arrays. Therefore, the effect of trapped charges on relaxation was also studied via monitoring the relaxation behaviours of homo-polymer and block copolymer films as well as measuring the mechanical properties of homo-polymers with charge patterns. These results demonstrate that the charge trapped in polymer electrets could accelerate relaxation and drive the dewetting process of thin polymer films.