RESUMEN
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is widely used because of its excellent performance. We report the synthesis of two PEDOT:PSS dispersions. The two dispersions differ by the addition of additional protonic acid in the oxidative polymerization system. Although there are examples of the introduction of acids into the polymerization system, the effects of acid on the structure and properties of these materials, in particular their mechanisms of action, have not been elucidated. We describe the chemical structure and molecular weight of two PEDOT polymers using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-vis-NIR spectroscopy, and density functional theory calculations. The carrier concentration, carrier mobility, and surface morphology of the composites are characterized by UV-vis-NIR spectroscopy, electron spin resonance, Raman spectra, Hall effect measurements, and atomic force microscopy. The crystallinity of PEDOT:PSS was measured by X-ray diffraction patterns. We show that the addition of a proper amount of protonic acid to the oxidative polymerization system can effectively reduce the formation of the terminal carbonyl group of PEDOT chains, which is conducive to the growth of polymer chains, and further improve the carrier concentration, which leads to an improvement of conductivity. Our results highlight the optimization of the chemical structure of PEDOT in order to increase its molecular weight and ultimately its conductivity.
RESUMEN
The characteristics of biochar are of great significance to its application in the field of phase change energy storage. The objective of this research was to explore the effects of pyrolysis temperature on the characteristics of a biochar matrix and further on the heat energy storage properties of the promising green biochar-supported shape-stable biocomposite PCMs (ss-BCPCMs). Corn straw biochars (CSBCs) obtained under different pyrolysis conditions were loaded with polyethylene glycol (PEG) by an ultrasound-assisted vacuum impregnation method. The micro-morphology, specific surface area, pore structure and surface properties of biochar have been characterized and analyzed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) method and Fourier transform infrared spectroscopy (FTIR). The thermal properties (chemical stability, latent heat storage, thermal conductivity, thermal stability, and thermal insulation) of PEG/CSBC composites have been characterized by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and laser flash analysis (LFA). The study revealed that both pore structure and surface activity of biochar are key factors affecting the energy storage performance of biochar-based ss-BCPCMs. The obtained PEG/CSBC composite showed a high latent heat storage up to 100.2 J g-1, good shape stability and leakage resistance, suggesting its high thermal storage stability that is beneficial for thermal energy storage applications. In addition, its excellent photothermal conversion efficiency (68.95%) provides application potential in photothermal energy storage.
RESUMEN
In this work, we creatively obtained reinforced and toughened PC/PMMA/GNs composites by tuning the migration and selective location of graphene nanosheets (GNs) during melt blending. TEM results revealed that the migration of GNs in PC/PMMA blends during melt blending always existed no matter how the GNs were introduced, and most of them exclusively localized at the interface of PC and PMMA phase due to interfacial effects. The migration of GNs could refine the size of the dispersed phase, and the exclusive localization of GNs at the interface show obvious interfacial compatibilizing effects, leading to improved mechanical properties of the composites. It was found that the composite prepared by one-step compounding showed significant enhanced strength and toughness with addition of mere 0.05 wt% GNs and the tensile strength and elongation of the composite increased by about 62.96% and 94.54%, respectively as compared to the PC/PMMA blends. Moreover, the composite prepared by one-step compounding also showed improved thermal conductivity at the same time, indicating excellent comprehensive properties. It is believed that tuning the migration and selective localization of GNs open perspectives for the development of high-performance polymer composites.
RESUMEN
In this work, a simple and eco-friendly strategy to modify graphene nanoplatelets (GNs) with different silane coupling agents using a supercritical carbon dioxide (Sc-CO2) process has been presented, and effect of the modified GNs on the oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of GN/PET composite films was studied. FT-IR, SEM, EDX and TG results indicated that Sc-CO2 process was an effective strategy to modify GNs with silane coupling agents. Addition of the modified GNs into PET matrix could greatly decrease the OTR and WVTR values of the GNs/PET composite films, and the WVTR of GNs560/PET composite film and OTR of GNs550/PET composite film were respectively decreased about 90.08% and 58.04%, as compared to those of GNs/PET composite film. It is found that the gas barrier property of GN/PET composites was attributed to not only the tortuous path effect caused by GNs themselves and the interfacial interaction, but also the affinity of binding bonds between GNs and the polymer to the gas molecules. It is believed that this work provided a strategy to design and prepare CN/polymer composites with high barrier properties.
