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

Abstract

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 1.03×10−10±1.3×10−11 and 1.08×10−10±5.8×10−12S·cm−1, respectively; whereas, upon reduction, the conductivity of p(HEMA)-r-GO cryogel composites increased to 4.80×10−7±5.9×10−8S·cm−1 (~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 1.38×10−4±2.5×10−5S·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 15min HCl gas exposure, and decreased 4-fold after 15min 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 15min exposures to HCl and NH3 gas, respectively.