Polymeric monolithic materials: Syntheses, properties, functionalization and applications

The synthetic particularities for the synthesis of polymer-based monolithic materials are summarized. In this context, monoliths prepared via thermal-, UV- or electron-beam triggered free radical polymerization, controlled TEMPO-mediated radical polymerization, polyaddition, polycondensation as well as living ring-opening metathesis polymerization (ROMP) will be covered. Particular attention is devoted to the aspects of controlling pore sizes, pore volumes and pore size distributions as well as functionalization of these supports. Finally, selected, recent applications in separation science, (bio-) catalysis and chip technology will be summarized. © 2007 Elsevier Ltd. All rights reserved

Polymeric monolithic materials: Syntheses, properties, functionalization and applications

The synthetic particularities for the synthesis of polymer-based monolithic materials are summarized. In this context, monoliths prepared via thermal-, UV- or electron-beam triggered free radical polymerization, controlled TEMPO-mediated radical polymerization, polyaddition, polycondensation as well as living ring-opening metathesis polymerization (ROMP) will be covered. Particular attention is devoted to the aspects of controlling pore sizes, pore volumes and pore size distributions as well as functionalization of these supports. Finally, selected, recent applications in separation science, (bio-) catalysis and chip technology will be summarized. © 2007 Elsevier Ltd. All rights reserved

a structure-activity correlation

The polymerization of octamethylcyclotetrasiloxane (D4) is investigated using several five-, six- and seven-membered N-heterocyclic carbenes (NHCs). The catalysts are delivered in situ from thermally susceptible CO2 adducts. It is demonstrated that the polymerization can be triggered from a latent state by mild heating, using the highly nucleophilic 1,3,4,5-tetramethylimidazol-2-ylidene as organocatalyst. This way, high molecular weight PDMS is prepared (up to >400 000 g/mol, 1.6 < ÐM < 2.5) in yields >95%, using low catalyst loadings (0.2–0.1 mol %). Furthermore, the results suggest that a nucleophilic, zwitterionic mechanism is in operation, in preference to purely anionic polymerization

Olefin Ring‐closing Metathesis under Spatial Confinement: Morphology−Transport Relationships

Spatial confinement effects on hindered transport in mesoporous silica particles are quantified using reconstructions of their morphology obtained by electron tomography as geometrical models in direct diffusion simulations for passive, finite‐size tracers. We monitor accessible porosity and effective diffusion coefficients resulting from steric and hydrodynamic interactions between tracers and pore space confinement as a function of λ=d$_{tracer}$/d$_{meso}$, the ratio of tracer to mean mesopore size. For λ=0, pointlike tracers reproduce the true diffusive tortuosities. For λ>0, derived hindrance factors quantify the extent to which diffusion through the materials is hindered compared with free diffusion in the bulk liquid. Morphology‐transport relationships are then discussed with respect to the immobilization, formation, and transport of key molecular species in the ring‐closing metathesis of an α,ω‐diene to macro(mono)cyclization product and oligomer, with a 2nd‐generation Hoveyda‐Grubbs type catalyst immobilized inside the mesopores of the particles

A new continuum model of Metal-Sulfurized Polyacrylonitrile (SPAN) batteries

Metal-sulfur (Me-S) batteries present a promising class of next-generation batteries with very high theoretical capacity. In recent years, magnesium (Mg) was proposed as anode material for Me-S bat-teries due to negligible dendrite formation and high volumetric capacity (3837 mAh/cm3) [1]. This ca-pacity is even higher than in Li-based systems (2062 mAh/cm3), which is very attractive for portable applications. However, similarly to Li-S batteries, Mg-S batteries show a low coulombic efficiency and fast self-discharge due to the polysulfide shuttle. In order to reduce the polysulfide shuttle, several mitigation strategies have been developed for Li-S batteries and some of these concepts have been also transferred to Mg-S batteries [2]. One promising approach is to covalently bind the sulfur to a polymer backbone. Long cycle life and high specific capacities have been demonstrated for sulfurated poly(acrylonitrile) (“SPAN”) cathodes in lithium-based batteries and, more recently, the proof-of-concept was also demonstrated for Mg-SPAN batteries [3,4]. In our contribution we present a novel continuum model for SPAN electrodes and demonstrate its application to Li-SPAN and Mg-SPAN batteries. Within our simulation framework [5] we are able to include both red/ox reactions of sulfur covalently bound to the polymeric backbone of SPAN and transport as well as electrochemical reactions of the polysulfides in solution. Additionally, we model side reactions on the negative electrode and precipitation of the solid discharge products. By com-paring our simulation results to experimental data, such as the cell voltage during galvanostatic cy-cling, we are able to identify qualitative differences between the Li- and Mg-based systems. The simulations provide insights on limiting factors for battery performance, which is the basis to guide new developments for Me-SPAN batteries

A novel Modeling Approach for Metal-SPAN Batteries

Metal-sulfur (Me-S) batteries present a promising class of next-generation batteries with very high theoretical capacity. In recent years, magnesium (Mg) was proposed as anode material for Me-S batteries due to negligible dendrite formation and high volumetric capacity (3,837 mAh/cm3). This capacity is even higher than in the Li system (2,062 mAh/cm3) which is very attractive for portable applications. However, similarly to Li-S batteries, Mg-S batteries show a low coulombic efficiency and fast self-discharge due to the polysulfide shuttle. In order to reduce the polysulfide shuttle several mitigation strategies have been developed for Li-S batteries and some of these concepts have been also transferred to Mg-S batteries. One promising approach is to covalently bond the sulfur to a polymer backbone. Long cycle life and high specific capacities could be shown for sulfurated Poly(acrylonitrile) (SPAN) cathodes in lithium-based batteries and more recently the proof-of-concept was also demonstrated for Mg-SPAN batteries. In our contribution, we will present a novel continuum model for SPAN electrodes and demonstrate its application in Li and Mg-SPAN batteries. Within our simulation framework we are able to include both red/ox reactions of covalently bond sulfur on PAN as well as transport and electrochemical reactions of polysulfides in solution. By comparing our simulation results to experimental data, we are able to identify qualitative differences in the sulfur reduction mechanism between the Li and Mg based system. In collaboration with our experimental partners, we aim to provide more insights on degradation mechanisms and limiting factors for battery performance which are able to guide new developments for Me-SPAN batteries

A Novel Continuum Model and Simulation Study Of Magnesium-Sulfur Battery With Sulfurized Polyacrylonitrile (SPAN) Cathodes

Magnesium-Sulfur (Mg-S) batteries are considered as promising contender for the next generation batteries due to its set of advantages: high gravimetric energy density (3.837 mAh/cm3), its abundancy, absence of scarce elements such as nickel or cobalt, and its reduced tendency to dendrite formation [1]. Unfortunately, sulfur-based batteries suffer from low coulombic efficiency and fast self-discharge due to the polysulfide shuttle. Several mitigation strategies to reduce the polysulfide shuttle effect have been developed and transferred to Mg-S batteries [2]. One of the promising approaches is to covalently bind the sulfur to a polymer backbone. Long cycle life and high specific capacities have been demonstrated for Sulfurated Poly(acrylonitrile) (SPAN) cathodes for Mg-SPAN batteries [3,4]. We present a novel continuum model for Mg-SPAN battery, which includes both red/ox reactions of sulfur covalently bound to the polymeric backbone of SPAN, species transport, and electrochemical reactions of the polysulfides in solution. The model parameters are extracted from structural and electrochemical characterization, such that the measured discharge curves are reproduced. In our study, we discovered that for a case of denser electrode, the capacity faded quite significantly as the tortuosity value increases and hinders the diffusion process. This shows that the morphology study of electrode essential for upscaling an SPAN cathode based battery. In collaboration with our experimental partners, we aim on providing more insights into the degradation mechanisms and limiting factors for battery performance, which are able to guide new developments for Mg-SPAN batteries

Modeling and Simulation of Metal-Sulfur Battery with Sulfurized Polyacrylonitrile (SPAN) Cathodes

The increasing demand for rechargeable and high-energy density batteries for portable devices, electric vehicles, and large-scale stationary storage systems has driven the intensive research to find more sustainable and economical materials. Lithium–sulfur (Li–S) batteries have been considered as a promising material for next-generation batteries with very high theoretical capacity (2,062 mAh/cm3). However, repeated plating and stripping of Li can lead to the growth of dendrites that potentially cause short circuits and battery failure. In recent years, magnesium (Mg) was proposed as anode material for Metal-Sulfur (Me-S) batteries due to its reduced tendency to dendrite formation and high volumetric capacity (3,837 mAh/cm3) [1]. Unfortunately, similarly to Li-S batteries, Mg-S batteries show a low coulombic efficiency and fast self-discharge due to the polysulfide shuttleSeveral mitigation strategies to reduce the polysulfide shuttle effect, have been developed for Li-S batteries and some of these concepts have been also transferred to Mg-S batteries [2]. One of the promising approaches is to covalently bind the sulfur to a polymer backbone. Long cycle life and high specific capacities have been demonstrated for sulfurated poly(acrylonitrile) (SPAN) cathodes in lithium-based batteries and, more recently, the proof-of-concept was also shown for Mg-SPAN batteries [3,4]. In our contribution, we present a novel continuum model for SPAN electrodes and demonstrate its application to Me-SPAN batteries. Within our simulation framework we include both red/ox reactions of sulfur covalently bound to the polymeric backbone of SPAN and transport as well as electrochemical reactions of the polysulfides in solution. Model parameters are extracted from structural and electrochemical characterization of SPAN composite electrodes and we demonstrate that we were able to reproduce the measured discharge curves. Starting with this standard configuration we perform simulation studies to investigate the influence of electrode geometric parameters such as electrode thickness and tortuosity on Li-SPAN cell performance. Finally, we apply our model for the simulation of Mg-SPAN batteries with dual salt electrolyte and investigate the kinetic mechanism in this complex electrochemical system. In collaboration with our experimental partners, we aim on providing more insights into the degradation mechanisms and limiting factors for battery performance, which are able to guide new developments for Me-SPAN batteries