Novel Graphene Oxide Nanohybrid Doped Methacrylic Acid Hydrogels for Enhanced Swelling Capability and Cationic Adsorbability.

Yufei Liu,Jihe Du,Ying Lyu,Rubing Chen,Yongqin Hu,Jia An,Chen Hou,Meizhu Chen

doi:10.3390/polym13071112

Abstract

Novel versatile hydrogels were designed and composited based on covalent bond and noncovalent bond self-assembly of poly(methacrylic acid) (PMAA) networks and nanohybrids doped with graphene oxide (GO). The structures and properties of the neat PMAA and the prepared PMAA/GO hydrogels were characterized and analyzed in detail, using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, swelling and cationic absorption, etc. The swelling results showed that the water penetration follows the non-Fick transport mechanism based on swelling kinetics and diffusion theory. The swelling capacity of PMAA and composited PMAA/GO hydrogels toward pH, Na+, Ga2+, and Fe3+ was investigated; the swelling ratio was tunable between 4.44 and 36.44. Taking methylene blue as an example, the adsorption capacity of PMAA/GO hydrogels was studied. Nanohybrid doped GO not only self-associated with PMAA via noncovalent bonding interactions and had a tunable swelling ratio, but also interacted with water molecules via electrostatic repulsion, offering a pH response of both the network and dye absorption. Increases in pH caused a rise in equilibrium swelling ratios and reduced the cumulative cationic dye removal.

Highlights

Hydrogels, either chemically or physically crosslinked, are mostly spontaneously formed as they capture water within their structure, having excellent and unique characteristics such as high hydrophilicity, elastic structure, and smart stimulus response, suitable for biomedicine [1,2], artificial muscles [3], robot actuators [4,5], adsorbents of toxic chemicals and wastewater [6,7], and drug delivery [8,9,10,11] applications
An Fourier transform infrared (FTIR) spectrophotometer was used to determine the functional groups of the original graphene oxide (GO) and the prepared poly(methacrylic acid) (PMAA)/GO hydrogel
The characteristic diffraction peak of GO (2θ = 9.92◦) disappeared in the X-ray diffraction (XRD) spectrum of the PMAA/GO hydrogel, which indicated that the GO flakes were exfoliated and dispersed well, that it is well-compatible with the PMAA polymer network, and that the PMAA polymers are entangled with each other to form a PMAA/GO composite hydrogel

Summary

Introduction

Either chemically or physically crosslinked, are mostly spontaneously formed as they capture water within their structure, having excellent and unique characteristics such as high hydrophilicity, elastic structure, and smart stimulus response, suitable for biomedicine [1,2], artificial muscles [3], robot actuators [4,5], adsorbents of toxic chemicals and wastewater [6,7], and drug delivery [8,9,10,11] applications Their characteristics are dependent on changes in the external environment, such as pH, ionic strength, electrical stimulation [12], and temperature. Cao et al applied the open framework structure Na3V2(PO4)3@C as a novel faradaic electrode in the hybrid capacitive deionization (HCDI) system, and its outstanding performance demonstrated its promise as a material for desalination [25]

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