First Network Research Articles

A tough double-network ion gel membrane based on poly (ionic liquid) for efficient carbon capture

Ion gel membranes show great potential for carbon capture due to their excellent solubility selectivity for CO2. However, poor mechanical properties and limited stability as well as low gas permeability limit their application. Here, we report a environmentally friendly and simple strategy for preparing double-network(DN) ion gel membranes with both high strength and excellent gas separation performance. We use a “one-pot method” that the first network(FN) and the second network(SN) with ionic liquid were mixed evenly, and the DN membrane was prepared under heating and UV light. Wherein the FN was obtained by a ring-opening reaction between O, O-bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol and a trimethylolpropane triglycidyl ether. And the SN was obtained by free radical polymerisation between 1 and vinyl-3-ethylimidazole bis(trifluoromethanesulfonyl)imide and a p-divinylbenzene (DVB) crosslinker. The crosslinking density of FN and SN, the mass ratio of the FN to the SN, as well as the content and type of free ionic liquid were optimized to improve the mechanical and gas separation properties of the DN membrane. When the crosslinking groups reacted quantitatively, the tensile strength of DN membranes is 1.5 MPa and the elongation at break is 120 %. With the increase of free ILs content, the crystallinity as well as the glass transformation temperature of the DN membrane decreases and the CO2 permeability increases (PCO2:866 Barrer α (CO2/N2):31). When 1-ethyl-3-methylimidazolium dicyanamide was used, the CO2/N2 separation performance can surpass the 2008 upper bound (PCO2:464 Barrer α (CO2/N2):63). The DN membrane has better gas separation and mechanical properties than the SN membrane and shows superior combination of the permeability and selectivity. This research provides a new approach designing a tough ion gel membrane which shows great potential for practical application in carbon capture.

Swelling-induced Mechanochromism in Multinetwork Polymers.

We report a novel and versatile approach to achieving swelling-induced mechanochemistry using a multinetwork (MN) strategy that enables polymer networks to repeatedly swell with monomers and solvents. The isotropic expansion of the first network (FN) provides sufficient force to drive the mechanochemical scission of a radical-based mechanophore, difluorenylsuccinonitrile (DFSN). Although prompt recombination generally occurs in such highly mobile environments, the resulting pink radicals are kinetically stabilized in the gels, probably due to limited diffusion in the extended polymer chains. Moreover, the DFSN embedded in the isotropically strained chain exhibits increased thermal reactivity, which can be reasonably explained by an entropic contribution of the FN to the dissociation. The utility of the MN polymers is demonstrated not only in terms of swelling-force-induced network modification, but also in the context of tunable reactivity of the dissociative unit through proper design of the hierarchical network architecture.

Swelling‐induced Mechanochromism in Multinetwork Polymers

AbstractWe report a novel and versatile approach to achieving swelling‐induced mechanochemistry using a multinetwork (MN) strategy that enables polymer networks to repeatedly swell with monomers and solvents. The isotropic expansion of the first network (FN) provides sufficient force to drive the mechanochemical scission of a radical‐based mechanophore, difluorenylsuccinonitrile (DFSN). Although prompt recombination generally occurs in such highly mobile environments, the resulting pink radicals are kinetically stabilized in the gels, probably due to limited diffusion in the extended polymer chains. Moreover, the DFSN embedded in the isotropically strained chain exhibits increased thermal reactivity, which can be reasonably explained by an entropic contribution of the FN to the dissociation. The utility of the MN polymers is demonstrated not only in terms of swelling‐force‐induced network modification, but also in the context of tunable reactivity of the dissociative unit through proper design of the hierarchical network architecture.

Reconstrucción de señales periódicas usando redes neuronales

En este artículo se reconstruye una señal periódica por medio de 2 redes neuronales. La primera es entrenada para aproximar el periodo de la señal, y la segunda sirve para estimar los coeficientes de la expansión de Fourier correspondientes. La estrategia consiste en minimizar el error medio cuadrático por medio del algoritmo de propagación hacia atrás sobre una neurona con función de transferencia senoidal. Además, en este artículo se presenta la prueba matemática acerca de la calidad de la aproximación, así como una primera modificación del algoritmo, la cual permite alcanzar el mismo resultado con menos datos, así entonces el algoritmo podría ser utilizado en aplicaciones que requieran tiempo real

INFLUENCE OF POLY(ETHYLENE GLYCOL) ON PROPERTIES OF PAMPS/PAM DOUBLE NETWORK HYDROGELS

Double network (DN) hydrogels composing of poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) as the first network (FN) and poly(acrylamide) (PAM) as the second network (SeN),which were prepared by ultraviolet irradiation polymerization,were modified by poly( ethylene glycol) ( PEG). By adding PEG into single network (SN) hydrogels,many tiny meshes have been made in the network structures; meanwhile the PAM particles of SeN are in different sizes. DN hydrogels modified by PEG become tougher and softer than those without PEG. The swelling behavior was measured gravimetrically at 28℃. The absorbed amount of acrylamide (AM) in SN hydrogels was measured by brominate titration. The structures of different SN hydrogels were successfully characterized by scanning electron microscopy ( SEM). The compressive and tensile properties were examined by using Zwick /Roell tester. The results showed that:this PEG modified DN hydrogels exhibited higher swelling ratio than that of unmodified DN hydrogels,the former was twice times higher than the latter. Interestingly,the volume of DN hydrogels became larger with the gradual increasing amount of PEG in the hydrogels,likewise,the transmittance of DN hydrogels with various PEG amounts became lower. Modified SN hydrogels prefer to absorb AM,because the small meshes,which are in the network of hydrogels,enhance the absorbability of water and AM. Pictures of SEM demonstrate apparently that many small meshes of about 0. 05 ～ 10 μm are in the network structures and the thickness of mesh walls ranges from 0. 02 μm to 0. 2 μm. However,in the unmodified SN hydrogels no obvious meshes were found and the thickness of mesh walls is about 3 μm. Some compressive and tensile properties were enhanced,for example when the PEG = 1. 0 g,the compressive strain of modified DN hydrogels was 90% ,while that of the unmodified ones was 80%. Twice times higher tensile strain than that of unmodified DN hydrogels indicated that modified DN hydrogels had become tougher and softer.