Site Dependent Atom Type ReaxFF for the Proton-Catalyzed Twin Polymerization

Prehl, Janett; Schönfelder, Thomas; Friedrich, Joachim; Hoffmann, Karl Heinz

doi:10.1021/acs.jpcc.7b03219

Cited by 6 publications

(7 citation statements)

References 43 publications

(67 reference statements)

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“…Atomistic simulations provide fundamental mechanistic insights into reactive processes and their consequences in polymeric materials that are difficult to elucidate from experiments alone. ,, Reactive force fields used with classical all-atom molecular dynamics (MD) are capable of reaching large time and space scales but frequently are not transferable to regions of chemical phase space beyond their fitting regime without extensive tuning. − In contrast, quantum-based molecular dynamics (QMD) provides an accurate and transferable approach to predict condensed-phase chemistry. However, the extreme computational expense of QMD simulations with ab initio methods such as density functional theory (DFT) places significant limitations on the accessible time and length scales that can be studied.…”

Section: Introductionmentioning

confidence: 99%

Chemical Degradation Pathways in Siloxane Polymers Following Phenyl Excitations

2018

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We use ensembles of quantum-based molecular dynamics simulations to predict the chemical reactions that follow radiation-induced excitations of phenyl groups in a model copolymer of polydimethylsiloxane and polydiphenylsiloxane. Our simulations span a wide range of highly porous and condensed phase densities, and include both wet and dry conditions. We observe that in the absence of water, excited phenyl groups tend to abstract hydrogen from other methyl or phenyl side groups to produce benzene, with the under-hydrogenated group initiating subsequent intrachain cyclization reactions. These systems also yield minor products of diphenyl moieties formed by the complete abstraction of both phenyl groups from a single polydiphenylsiloxane subunit. In contrast, we find that the presence of water promotes the formation of free benzene and silanol side groups, reduces the likelyhood for intrachain cyclization reactions, and completely suppresses the formation of diphenyl species. In addition, we predict that water plays a critical role in chain scission reactions, which indicates a possible synergistic effect between environmental moisture and radiation that could promote alterations of a larger polymer network. These results could have impact in interpreting accelerated aging experiments, where polymer decomposition reactions and network rearrangements are thought to have a significant effect on the ensuing mechanical properties. 1 Introduction Polysiloxane-based materials, or silicones, are widely used in a range of technological applications where favorable long term mechanical response, chemical inertness, and shape filling factor over a broad temperature range are required. Applications include space-filling rubber or foam gaskets and shock absorbers to biomedical implants, lubricants, and adhesives. 1,2 Many applications of silicone rubber and foam components have specific requirements for mechanical properties such as elastic moduli (bulk, Young's, and shear), viscoelastic response, and hardness. The mechanical properties of silicones are often tuned by controlling

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Section: Introductionmentioning

confidence: 99%

Chemical Degradation Pathways in Siloxane Polymers Following Phenyl Excitations

2018

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“…As shown in Figure 3 1 twin polymerizes to a phenolic resin ( 2 ) and silica network ( 3 ). From experimental [6,7,8,10,29,30] and theoretical [8,14,15,16,17,18] investigations it is known, that the acid catalyzed reaction mechanism is a reaction in a melt [8]. It can be characterized by three main reaction steps.…”

Section: Numerical Model Materials and Methodsmentioning

confidence: 99%

“…First, the methylene bonds open (ring opening process), second, the organic network formation via organic bond formations starts, and third, somehow later the inorganic network formation starts by opening the aryl bonds and forming the siloxane bonds at the same time. For further details to the reaction mechanism we refer the reader to [17,18,19].…”

Section: Numerical Model Materials and Methodsmentioning

confidence: 99%

“…Important questions like: “Which elements of the twin monomer structure need to be changed to obtain an nanoporous hybrid materials with a desired pore size distribution?” or “Where to tune the reaction mechanism to generate a specific application based material with desired specific surface area?” are still difficult to answer. To bridge this gap, in the last years several theoretical approaches [9,14,15,16,17,18,19] at different levels of detail have been established. From these investigations, we gain important insights into the reaction mechanism of the thermal, acid- and base-induced twin polymerization.…”

Section: Introductionmentioning

confidence: 99%

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Morphology on Reaction Mechanism Dependency for Twin Polymerization

Prehl

Huster

2019

Polymers

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An in-depth knowledge of the structure formation process and the resulting dependency of the morphology on the reaction mechanism is a key requirement in order to design application-oriented materials. For twin polymerization, the basic idea of the reaction process is established, and important structural properties of the final nanoporous hybrid materials are known. However, the effects of changing the reaction mechanism parameters on the final morphology is still an open issue. In this work, the dependence of the morphology on the reaction mechanism is investigated based on a previously introduced lattice-based Monte Carlo method, the reactive bond fluctuation model. We analyze the effects of the model parameters, such as movability, attraction, or reaction probabilities on structural properties, like the specific surface area, the radial distribution function, the local porosity distribution, or the total fraction of percolating elements. From these examinations, we can identify key factors to adapt structural properties to fulfill desired requirements for possible applications. Hereby, we point out which implications theses parameter changes have on the underlying chemical structure.

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“…A series of detailed computational studies on the mechanisms of the TP process was reported. [16,[74][75][76][77][78][79] For example, a scale bridging approach was presented to simulate 2,2'spirobi[benzo-4H-1,3,2-dioxasiline] TP at the DFT level of theory giving insight into the structure as well as the reactivity at the molecular level. [16] This was later extended to include the influence of the counter anion of the used trifluoroacetic acid.…”

Section: Hybrid Materials Formation and Mechanismsmentioning

confidence: 99%

Twin Polymerization: A Unique Strategy towards Versatile Functional Materials

Scharf,

Notz,

Lang

2023

Eur J Inorg Chem

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Twin polymerization (=TP), a non‐aqueous synthetic methodology for the preparation of inorganic‐organic hybrid materials, by using, for example, salicylic‐ or furfurylic‐functionalized main‐group elements and/or transition metal‐based twin monomers, results in the formation of interpenetrating phase (nano)domains in a single step. The chemical, analytical and physical properties including theoretical studies of the (co)polymerization process of the respective twin monomers, polymers and the as‐generated hybrid and composite materials are described. Furthermore, the synthesis of hierarchical materials such as carbon hollow spheres as well as the encapsulation of nanoparticles (=NPs) within them by applying TP is envisaged. TP gives access to a wide range of applications (e. g., coatings for a variety of substrates, textile functionalization, carbon materials for Li−S or redox‐flow batteries) which will be discussed herein. The use of NP‐decorated hybrid and composite materials and nanoparticular MgO as catalysts in heterogeneous catalysis is reported as well.

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Site Dependent Atom Type ReaxFF for the Proton-Catalyzed Twin Polymerization

Cited by 6 publications

References 43 publications

Chemical Degradation Pathways in Siloxane Polymers Following Phenyl Excitations

Chemical Degradation Pathways in Siloxane Polymers Following Phenyl Excitations

Morphology on Reaction Mechanism Dependency for Twin Polymerization

Twin Polymerization: A Unique Strategy towards Versatile Functional Materials

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