Electrically Conductive,\nTough Hydrogels with pH Sensitivity

Abstract

Electrically conductive, mechanically tough hydrogels\nbased on a double network (DN) comprised of poly­(ethylene glycol)\nmethyl ether methacrylate (PPEGMA) and poly­(acrylic acid) (PAA) were\nproduced. Poly­(3,4-ethylenedioxythiophene) (PEDOT) was chemically\npolymerized within the tough DN gel to provide electronic conductivity.\nThe effects of pH on the tensile and compressive mechanical properties\nof the fully swollen hydrogels, along with their electrical conductivity\nand swelling ratio were determined. Compressive and tensile strengths\nas high as 11.6 and 0.6 MPa, respectively, were obtained for hydrogels\ncontaining PEDOT with a maximum conductivity of 4.3 S cm^–1. This conductivity is the highest yet reported for hydrogel materials\nof high swelling ratios. These hydrogels may be useful as soft strain\nsensors because their electrical resistance changed significantly\nwhen cyclically loaded in compression.