Nanocomposites of co-poly (vinyl chloride–polyvinyl acetate–polyvinyl alcohol) (PVC–PVAc–PVA) and kaolinite were prepared via solution intercalation technique. To improve compatibility among the phases and to expand the interlayer basal spacing, kaolinite was modified using dimethylsulfoxide (DMSO) as a swelling agent. The influence of kaolinite dispersion and interaction between the disparate phases on the properties of nanocomposites were investigated using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical testing, thermogravimetric analysis (TGA) and water absorption measurements. IR data confirmed the hydrogen bonds formed between DMSO and the surface hydroxyl groups of kaolinite. XRD and microscopic results revealed that clay mineral was intercalated with uniform dispersion at nanoscale in the matrix. Tensile testing of these materials indicated significant improvements in the mechanical properties relative to the pure copolymer. Incorporation of kaolinite into the organic phase enhanced the thermal stability of the nanocomposites. Water absorption of the nanomaterials was reduced upon the addition of modified kaolinite rendering decreased permeability with increasing dispersibility of clay mineral in the copolymer matrix.
Synthesis of nanoporous 1,2,4-oxadiazole networks with high CO2 capture capacity
Developing an adsorbent to mitigate carbon dioxide without large energy penalty is highly desired. Here, we present a silylation synthetic route to form a processable and otherwise impossible porous 1,2,4-oxadiazole network, which achieves 2 mmol g−1 of CO2 capacity owing to a nitrogen-rich structure. This network shows high CO2–N2 selectivity, thermal stability up to 450 °C, and low heat of adsorption (26.4 kJ mol−1), facilitating easy regeneration.
A half millimeter thick coplanar flexible battery with wireless recharging capability
J. S. Kim, D. Ko, D. J. Yoo, D. S. Jung, C. T. Yavuz, N. I. Kim, I. S. Choi, J. Y. Song, J. W. Choi
Most of the existing flexible lithium ion batteries (LIBs) adopt the conventional cofacial cell configuration where anode, separator, and cathode are sequentially stacked and so have difficulty in the integration with emerging thin LIB applications, such as smart cards and medical patches. In order to overcome this shortcoming, herein, we report a coplanar cell structure in which anodes and cathodes are interdigitatedly positioned on the same plane. The coplanar electrode design brings advantages of enhanced bending tolerance and capability of increasing the cell voltage by in series-connection of multiple single-cells in addition to its suitability for the thickness reduction. On the basis of these structural benefits, we develop a coplanar flexible LIB that delivers 7.4 V with an entire cell thickness below 0.5 mm while preserving stable electrochemical performance throughout 5000 (un)bending cycles (bending radius = 5 mm). Also, even the pouch case serves as barriers between anodes and cathodes to prevent Li dendrite growth and short-circuit formation while saving the thickness. Furthermore, for convenient practical use wireless charging via inductive electromagnetic energy transfer and solar cell integration is demonstrated.
A novel, reactive green iron sulfide (sulfide green rust) formed on iron oxide nanocrystals
C. Jones, S. Chattopadhyay, N. I. Gonzalez-Pech, C. Avendano, N. Hwang, S. S. Lee, M. Cho, A. Ozarowski, A. Prakash, J.T. Mayo, C. Yavuz, V. L. Colvin
Iron oxide nanocrystals are of great scientific and technological interest. In this work, these materials are the starting point for producing a reactive nanoparticle whose surface resembles that of natural green rusts. Treatment of iron oxide nanoparticles with cysteamine leads to the reduction of iron and the formation of a brilliant green aqueous solution of nanocrystals rich in iron(II). These materials remained crystalline with magnetic and structural features of the original iron oxide. However, new low-angle X-ray diffraction peaks as well as vibrational features characteristic of cysteamine were found in the nanocrystalline product. X-ray absorption spectroscopy (XAS), X-ray photoemission (XPS) and Mössbauer spectroscopies indicated the presence of an iron(II)-rich phase with high sulfur content analogous to the iron–oxygen structures found in natural green rusts. Electron microscopy found that these structural components remained associated with the nonreduced iron oxide cores. These sulfur-rich analogs of natural green rusts are highly reactive and were able to rapidly degrade a model organic dye in water. This observation suggests possible actuation with a cysteamine treatment of inert and magnetic iron oxide particles at the point-of-use for environmental remediation.
Nanoporous benzoxazole networks by silylated monomers, their exceptional thermal stability and carbon dioxide capture capacity
The pursuit of synthetic routes for design and preparation of nanoporous polymeric networks with inherent permanent microporosity and functionality through bottom-up methodologies remains a driving force in developing CO2-philic materials. We report nanoporous, processable, benzoxazole-linked covalent organic polymers (Box-COPs) that show exceptional thermal stability up to 576 °C. Box-COPs can be formed into films thanks to the silylation that is used to guide polymeric network formation. Surface areas of up to 606 m2 g–1 and narrow pore sizes of 4.36 Å were observed with a CO2 uptake capacity of 139.6 mg g–1 at 273 K and 1 bar. Box-COPs were stable in boiling water for a week without deteriorating CO2 capture capacity.
Charged induced formation of crystalline network polymers
Order in purely organic network polymers is hard to achieve, as reversible, dynamic covalent bond formation is required. Strategies have focused on thermodynamically controlled transformations, as kinetics would not seemingly favour reversibility. Herein, we report formation of crystalline network polymers under kinetically favoured conditions by using quaternary ammonium salt linked networks. Charged bulky bridges align, even under fast reaction times (20 minutes) if the rotational freedom is granted. Adding vicinal methyl substituents blocks the ordering, hence forming amorphous networks. Raman experiments and SEM images reveal stacking of 2D layers.
Download
doi :
