The use of graphene oxide-embedded superporous poly(2-hydroxyethylmethacrylate) cryogels for p(aniline) conductive polymer synthesis and their use in sensor applications

Poly(2-hydroxyethylmethacrylate)-graphene oxide (p(HEMA)-GO) cryogel composites were prepared by including GO during cryopolymerization. The GO within p(HEMA) cryogels was reduced by treating p(HEMA)GO cryogel composites with the aqueous solutions of hydriodic acid, hydrazine, ascorbic acid, tannic acid, and sodium borohydride. The changes in conductivities of p(HEMA)-GO and its reduced forms, p(HEMA)-r-GO cryogel composites, were compared. The conductivity of bare p(HEMA), and p(HEMA)-GO cryogel were almost the same at 1.03 x 10(-10) +/- 1.3 x 10(-11) and 1.08 x 10(-10) +/- 5.8 x 10(-12) S.cm(-1), respectively; whereas, upon reduction, the conductivity of p(HEMA)-r-GO cryogel composites increased to 4.80 x 10(-7) +/- 5.9 x 10(-8) S.cm(-1) (similar to 4000-fold increase). Moreover, upon in situ synthesis of conductive polyaniline (p(An)) within p(HEMA)-r-GO cryogel composites as p(HEMA)-r-GO/p(An) semi-interpenetrating polymer network (semi-IPN), the conductivity increased 250-fold more than p(HEMA)-r-GO composite, and 1 million-fold more than the bare p(HEMA) or p(HEMA)-GO cryogels with a conductivity value of 1.38 x 10(-4) +/- 2.5 x 10(-5) S.cm(-1). Furthermore, p(HEMA)-r-GO composite and p(HEMA)-r-GO/p (An) composite semi-IPN conductive cryogel systems were tested as sensor materials for HCl and NH3 gases. The conductivity of p(HEMA)-r-GO composite increased 3-fold upon 15 min HCl gas exposure, and decreased 4-fold after 15 min NH3 gas exposure. Also, the conductivity of p(HEMA)-r-GO/p(An) composite semi-IPN conductive cryogel systems were increased 2-fold and decreased 46-fold upon 15 min exposures to HCl and NH3 gas, respectively. (C) 2017 Elsevier Ltd. All rights reserved.