Hydrogels in aqueous phases of polyvinylalcohol (PVA), surfactants and clay minerals

Few-layered MoS2/C with expanding d-spacing as a high-performance anode for sodium-ion batteries

Sodium-ion batteries (SIBs) show great potential as alternative energy storage devices for next generation energy storage systems due to the deficiency of lithium resources. MoS₂ is a promising anode material for SIBs due to its high theoretical sodium storage capability and large interspace for accommodating sodium ions with a larger ionic radius than lithium ions. However, bulk MoS₂ exhibits a sluggish kinetics for the intercalation-deintercalation of sodium ions and large volume expansion, which result in poor cyclability and rate performance. In this study, we designed few-layered MoS₂/C nanoflowers with expanded interspacing of MoS₂-MoS₂ planes using polyvinyl alcohol (PVA) as an intercalating reagent and a carbon precursor. Due to the unique nanostructure and larger interlayer spacing, the MoS₂/C nanoflower electrode achieves a high reversible specific capacity of 400 mA h g^-1 after 300 cycles at 500 mA g^-1 for sodium-ion batteries (SIBs), showing a good cycling stability. The improved electrochemical performance suggests that the MoS₂/C composite is a promising anode material for sodium ion storage.

Nanoparticles with entrapped α-tocopherol: synthesis, characterization, and controlled release

An emulsion evaporation method was used to synthesize spherical poly(DL-lactide-co-glycolide) (PLGA) nanoparticles with entrapped α-tocopherol. Two different surfactants were used: sodium dodecyl sulfate (SDS) and poly(vinyl alcohol) (PVA). For SDS nanoparticles, the size of the nanoparticles decreased significantly with the entrapment of α-tocopherol in the PLGA matrix, while the size of PVA nanoparticles remained unchanged. The polydispersity index after synthesis was under 0.100 for PVA nanoparticles and around 0.150 for SDS nanoparticles. The zeta potential was negative for all PVA nanoparticles. The entrapment efficiency of α-tocopherol in the polymeric matrix was approximately 89% and 95% for nanoparticles with 8% and 16% α-tocopherol theoretical loading, respectively. The residual PVA associated with the nanoparticles after purification was approximately 6% ( w/w relative to the nanoparticles). The release profile showed an initial burst followed by a slower release of the α-tocopherol entrapped inside the PLGA matrix. The release for nanoparticles with 8% α-tocopherol theoretical loading (86% released in the first hour) was faster than the release for the nanoparticles with 16% α-tocopherol theoretical loading (34% released in the first hour).

Supramolecular structures in nanocomposite multilayered films

We investigate the multilayered structures of poly(ethylene)oxide/montmorillonite nanocomposite films made from solution. The shear orientation of a polymer-clay network in solution combined with simultaneous solvent evaporation leads to supramolecular multilayer formation in the film. The resulting films have highly ordered structures with sheet-like multilayers on the micrometer length scale. The polymer covered clay platelets were found to orient in interconnected blob-like chains and layers on the nanometer length scale. Inside the blobs, scattering experiments indicate the polymer covered and stacked clay platelets oriented in the plane of the film. The polymer is found to be partially crystalline although this is not visible by optical microscopy. Atomic force microscopy suggests that the excess polymer, which is not directly adsorbed to the clay, is wrapped around the stacked platelets building blobs and the polymer also interconnects the polymer-clay layers. Overall our results suggest the re-intercalation of clay platelets in films made from exfoliated polymer-clay solutions as well as the supramolecular order and hierarchical structuring on the nanometer, via micrometer to the centimeter length scale.