A series of highly dielectric polyrotaxane derivatives consisting of axle polyethylene glycol (PEG) and threated alpha-cyclodextrins (CDs) were synthesized by Modifying the hydroxyl groups of CDs with cyanoethyl or dicyanobutyl groups. We found that the introduction of poly(2-hydroxyethyl methacrylate) (PHEMA) side chain with a number of hydroxyl groups and subsequent cyanoethylation give particularly high dielectric constant (23.4), which is comparable to those of commercially available highly dielectric polymeric materials. We also succeeded in preparing a highly dielectric (epsilon' similar to 16 at 10 kHz) and flexible (Young's modulus similar to 3.4 MPa) elastomer film without any inorganic filler, which is a desirable material for insulator of dielectric elastomer actuators. (C) 2014 Elsevier Ltd. All rights reserved.