Poly(2-hydroxyethyl acrylate) hydrogels reinforced with graphene oxide: Remarkable improvement of water diffusion and mechanical properties

[EN] A series of hybrid hydrogels of poly(2-hydroxyethyl acrylate), PHEA, and graphene oxide, GAO, with GAO content up to 2 wt % has been prepared by in situ polymerization. Because PHEA has been used as biomaterial in various applications, has a side chain with the hydroxyl functional group and its mechanical properties are poor, it is a good candidate for reinforcement with GAO. Fourier transform (infrared) spectroscopy, atomic force microscopy, differential scanning calorimetry, the thermal, mechanical, and water sorption properties of neat PHEA and PHEA/GAO composites have been studied in order to elucidate the dispersion and interaction between both components. An increase in the water diffusion coefficient and dramatic changes in its mechanical proper- ties are the most remarkable results. Thus, at a nanofiller load of 2 wt %, the novel materials present an increased diffusion coeffi- cient higher than 380% and the elastic modulus is enhanced by more than 650% in dry state and by more than 100% in swollen state, both compared to neat PHEA. These results have been attributed to the excellent interaction between the matrix, PHEA, and the reinforcement, GAO, and could open the door to new applications in the field of biomaterials with higher structural requisites.This work was supported by Project GV/2016/067 of the Generalitat Valenciana. AFM, and the stress-strain assay was conducted by the authors in the Microscopy Service of the Universitat Politecnica de Valencia, whose advice is greatly appreciated. The authors acknowledge M. Monleon-Pradas for his helpful discussions.Sánchez-Correa, FV.; Vidaurre Agut, CM.; Serrano Aroca, Á.; Campillo Fernández, AJ. (2018). Poly(2-hydroxyethyl acrylate) hydrogels reinforced with graphene oxide: Remarkable improvement of water diffusion and mechanical properties. Journal of Applied Polymer Science. 135(15). https://doi.org/10.1002/app.46158S1351

Effect of graphene-oxide enhancement on large-deflection bending performance of thermoplastic polyurethane elastomer

This paper was accepted for publication in the journal Composites Part B and the definitive published version is available at http://dx.doi.org/10.1016/j.compositesb.2015.11.033Thermoplastic polyurethane (PU) elastomers are used as shoe-sole materials due to many excellent properties but their inelastic deformation is a serious deficiency for such applications. Hence, graphene oxide (GO) was introduced into the synthesized thermoplastic PU to produce a GO/PU composite material with enhanced properties. Plastic behaviour of this composite was assessed in cyclic tensile tests, demonstrating reduction of irreversible deformations with the addition of GO. Additionally, in order to evaluate mechanical performance of PU and the GO/PU composite under conditions of large-deflection bending typical for shoe soles, finite-element simulations with Abaqus/Standard were conducted. An elastic-plastic finite-element model was developed to obtain detailed mechanical information for PU and the GO/PU composite. The numerical study demonstrated that the plastic area, final specific plastic dissipation energy and residual height for PU specimens were significantly larger than those for the GO/PU composite. Besides, the addition of GO into the PU matrix greatly delayed the onset of plastic deformation in PU in a large-deflection bending process. The average residual height and final specific plastic dissipation energy for PU were approximately 5.6 and 17.7 times as large as those for the studied GO/PU composite. The finite-element analysis provided quantification of the effect of GO enhancement on the large-deflection bending performance of PU for regimes typical for shoe soles and can be used as a basis for optimization of real composite products

Probing the Thermal Deoxygenation of Graphene Oxide using High Resolution In Situ X-Ray based Spectroscopies

Despite the recent developments in Graphene Oxide due to its importance as a host precursor of Graphene, the detailed electronic structure and its evolution during the thermal reduction remain largely unknown, hindering its potential applications. We show that a combination of high resolution in situ X-ray photoemission and X-ray absorption spectroscopies offer a powerful approach to monitor the deoxygenation process and comprehensively evaluate the electronic structure of Graphene Oxide thin films at different stages of the thermal reduction process. It is established that the edge plane carboxyl groups are highly unstable, whereas carbonyl groups are more difficult to remove. The results consistently support the formation of phenol groups through reaction of basal plane epoxide groups with adjacent hydroxyl groups at moderate degrees of thermal activation (~400 {\deg}C). The phenol groups are predominant over carbonyl groups and survive even at a temperature of 1000 {\deg}C. For the first time a drastic increase in the density of states (DOS) near the Fermi level at 600 {\deg}C is observed, suggesting a progressive restoration of aromatic structure in the thermally reduced graphene oxideComment: Pagona Papakonstantinou as Corresponding author, E-mail: [email protected]