Fe3O4 Nanoparticles Grown on Cellulose/GO Hydrogels as Advanced Catalytic Materials for the Heterogeneous Fenton-like Reaction

Cellulose/graphene oxide (GO)/iron oxide (Fe3O4) composites were prepared by coprecipitating iron salts onto cellulose/GO hydrogels in a basic solution. X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared, and X-ray diffraction characterization showed that Fe3O4 was successfully coated on GO sheets and cellulose. Cellulose/GO/Fe3O4 composites showed excellent catalytic activity by maintaining almost 98% of the removal of acid orange 7 (AO7) and showed stability over 20 consecutive cycles. This performance is attributable to the synergistic effect of Fe3O4 and GO during the heterogeneous Fenton-like reaction. Especially, the cellulose/GO/Fe3O4 composites preserve their activity by keeping the ratio of Fe3+/Fe2+ at 2 even after 20 catalysis cycles, which is supported by XPS analysis

Effect of surfactant and electron treatment on the electrical and thermal conductivity as well as thermal and mechanical properties of ehylene vinyl acetate/expanded graphite composites

This study presents an investigation of the electrical and thermal conductivities of composites based on an ethylene vinyl acetate (EVA) copolymer matrix and nanostructured expanded graphite (EG). To improve the EG dispersion in EVA, EG sheets were modified by treating them with the anionic surfactant sodium dodecyl sulphate (SDS) in water. The modified SDS-EG platelets, after being filtered and dried, were melt-mixed with EVA to prepare the composites. Finally, both EVA/EG and EVA/SDS-EG composites were subjected to 50 kGy electron beam (EB) irradiation. SEM images confirm that the irradiated EVA/EG samples had improved interfacial adhesion, while the irradiated EVA/SDS-EG samples showed even better interfacial adhesion. The gel contents of the irradiated samples without and with SDS treatment increased with increase in EG loading. The EVA/EG composites exhibited a sharp transition from an insulator to a conductor at an electrical percolation threshold of 8 wt %, but with SDS-EG the electrical conductivity was extremely low, showing no percolation up to 10 wt % of filler. The EB irradiation had no influence on electrical conductivity. The thermal conductivity linearly increased with EG content, and this increase was more pronounced in the case of SDS-EG, but decreased after EB irradiation. The thermal properties were little influenced by EB irradiation, while better polymer–filler interaction and better filler dispersion as a result of SDS treatment, and the EB irradiation initiated formation of a cross-linked network, had a positive effect on the tensile properties.National Research Foundation of South Africa (UID 73982) and the International Bureau of the BMBF in Germany (project SUA 10/009)

Revealing Fast Proton Transport in Condensed Matter by Means of Density Scaling Concept

Herein, we investigate the charge transport and structural dynamics in the supercooled and glassy state of protic ionic material with an efficient interionic Grotthuss mechanism. We found that superprotonic properties of studied acebutolol hydrochloride (ACB-HCl) depend on thermodynamic conditions with the most favorable regions being close to the glass-transition temperature (Tg) and glass-transition pressure (Pg). To quantify the contribution of fast proton hopping to overall charge transport over a broad T–P space, we employed the density scaling concept, one of the most important experimental findings in the field of condensed matter physics. We found that isothermal and isobaric dc-conductivity (σdc) and dynamic light scattering (τα) data of ACB-HCl plotted as a function of (TVγ)−1 satisfy the thermodynamic scaling criterion with the ratio γσ/γα appearing as a new measure of fast charge transport in protic ionic glass-formers in the T–P plane. Such a universal factor becomes an alternative to the well-known Walden rule being limited to ambient pressure conditions

Effect of High Pressure on Crystallization Kinetics of van der Waals Liquid: An Experimental and Theoretical Study

Theoretical and experimental studies on the crystallization of a supercooled liquid, dimethyl phthalate, are explored in a wide range of temperatures and pressures (up to 1.8 GPa). By considering only isochronal conditions, we were able to control molecular mobility and untangle the thermodynamic effects on crystallization from kinetic ones. The analysis of experimental results revealed that crystallization of supercooled dimethyl phthalate speeds up under pressure. However, at pressures higher than ca. 1.2 GPa, a sudden change in the crystallization tendency of the investigated material was observed. Thermodynamic aspects of the crystallization process under the invariable influence of the mobility factor were described theoretically within the formalism provided by Gutzow and co-workers [Gutzow, I. et al. J. Mater. Sci. 1997, 32, 5389−5403]. The validity of the classical approach applied to express thermodynamic parameters governing the liquid/crystal phase transition under compression is carefully discussed

Toward Better Understanding Crystallization of Supercooled Liquids under Compression: Isochronal Crystallization Kinetics Approach

In this paper, we present dielectric studies on the effect of different thermodynamic conditions on the physical stability of van der Waals glass-forming material of pharmaceutical interest, indomethacin. By maintaining isochronal condition during measurements, we were able to control the kinetic factor of the crystallization process and untangle purely thermodynamic effects on crystallization from kinetic ones. This cannot be achieved by any other experimental attempt performed at atmospheric pressure. Along with experimental studies, crystallization of supercooled indomethacin under pressure was described theoretically. We have demonstrated within the studied pressure range (0.1–220 MPa) that one should expect an increase of thermodynamic driving force, decrease in melt/crystal interface energy, and critical nuclei size. Therefore, an experimentally observed increase in the overall crystallization rate under isochronal conditions can be exclusively rationalized as due to variations of the thermodynamic factor

Effect of Cure Conditions on the Generated Morphology and Viscoelastic Properties of a Poly(acrylonitrile–butadiene–styrene) Modified Epoxy–Amine System

The curing behavior, phase morphology, and dynamic mechanical characteristics of an epoxy system based on the diglycidyl ether of bisphenol A (DGEBA) and 4,4′-diaminodiphenylsulfone (DDS), modified with different amounts of poly­(acrylonitrile–butadiene–styrene) (ABS), were investigated by employing differential scanning calorimetry (DSC), field-emission scanning electron microscopy (FESEM), and dynamic mechanical thermal analysis (DMTA). The effects of different curing conditions on the generated morphologies and viscoelastic properties were evaluated. The amounts of ABS in the epoxy blends were 3.6, 6.9, 10, and 12.9 wt %. The rate of the curing reaction decreased with increasing thermoplastic content and with decreasing curing temperature. Morphological analysis revealed a phase-separated morphology for the blend systems. The storage modulus (<i>E</i>′), loss modulus (<i>E</i>″), and tan δ values of the systems were measured as functions of temperature and are discussed based on the morphological behavior of the epoxy blends with different amount of ABS

Shape Memory Properties of Epoxy/PPO–PEO–PPO Triblock Copolymer Blends with Tunable Thermal Transitions and Mechanical Characteristics

In this paper, we report a simple method to prepare novel, transparent, hard-tough and hard-flexible shape memory, and soft-flexible epoxy polymers based on poly­(propylene glycol)-<i>block</i>-poly­(ethylene glycol)-<i>block</i>-poly­(propylene glycol) (PPO–PEO–PPO) triblock copolymer (TBCP) and diglycidyl ether of bisphenol A (DGEBA)/4,4′-diaminodiphenylmethane (DDM) system. The PPO–PEO–PPO triblock copolymer was used to tailor cross-link density and flexibility in epoxy thermosets and thereby their glass transition temperatures (<i>T</i>_g’s). The formed blends exhibit a phase-separated morphology. The phase separation was initiated by immiscible PPO blocks via self-assembly. Three types of shape memory polymers, viz., stiff, intermediate, and soft-flexible epoxy systems, with entirely different physical and mechanical properties were prepared only by adjusting the blend composition. All the blends were UV resistant, were thermally and dimensionally stable, and could be used for various outdoor applications. To the best of our knowledge, no work has been reported on the shape memory properties of epoxy modified block copolymers