Mechanochemical reactivity

The inclusion of internal viscosity raises considerably the free-energy storage capacity of a rapidly deforming macromolecule as compared to the idealized Hookean spring model and could play a decisive role in mechanochemical reactivity in transient elongational flow. 

Li W, Edwards SA, Lu L, Kubar T, Patil SP, Grubrniiller H, Groenhof G, Grater F (2013) Force distribution analysis of mechanochemically reactive dimethylcyclobutene. ChemPhysChem 14 2687... 

Fig. 7 Mechanochemical reactivity of gDFC. At high forces, cis- and trans-gOFC open to form a 1,3-diradical intermediate and A,ram respectively). Upon releasing the force (B), the inter-...

The standard type solid state reactivity is mechanochemical reactivity. This method has been referred to by as making crystals by smashing crystals. ... 

Figure 8.4 Schematic representation of the mechanochemical reactivity of caffeine, citric acid and their respective hydrates under neat and liquid-assisted grinding conditions. ...

Figure 5 Two examples of the mechanochemical synthesis of coordination polymers by ligand addition reactions (a) the synthesis of a 1-D coordination polymer from copper(II) acetylacetonate and bipy and (b) illustration of the difference in mechanochemical reactivity of bipy towards anhydrous CoClj and CoClj bHjO...

So far, all discussed examples of acid-base reactions used to construct coordination polymers involve soluble metal salts as precursors. Flowever, as mechanochemical reactivity is independent from the solubility of reactants, the use of slightly soluble but cleaner and readily available carbonate or oxide reactants is also possible. With oxide reactants, the highly basic nature of the oxide ion provides a strong driving force for the... 

Molecular Basis of Mechanochemical Degradation 3.1 Molecular Strain and Reactivity... 

Unusual reactivities of mechano-radicals have been reported in a few instances. To explain the pseudo first-order kinetics and the high yield of linear block copolymers formed during the mechanochemical degradation of a mixture of... 

In the absence of oxygen or any other radical trap, however, mechanochemically formed macroalkyl radicals (scheme I, I) can be made to react with chemically reactive modifiers, RM, (see scheme Id) this forms the basis of an in-situ synthesis of polymer adducts i.e., the functionalised additive/modifier becomes chemically bound onto the polymer backbone. 

In a variant of the second method described earlier the premixed metallic powders (or pulverized ingots) are milled under hydrogen atmosphere to directly form an intermetallic hydride. It can be also viewed as hydrogen alloying of metal powders and powder mixtures in hydrogen alloying mills. This method is called a reactive mechanical alloying (RMA) or mechanochemical synthesis (MCS). 

Mechanochemical synthesis (MCS) by reactive milling of metal powders or intermetaUics in hydrogen gas... 

Mechanochemical activation synthesis (MCAS) by reactive milling of componnds... 

Note Shearing, stretching, and grinding are typical methods for the mechanochemical generation of reactive sites, usually macroradicals, in polymer chains that undergo mechanochemical reactions. 

Note 1 Examples of reactive blending are (a) blending accompanied by the formation of a polymer-polymer complex, (b) the formation of block or graft copolymers by a combination of radicals formed by the mechanochemical scission of polymers during blending. 

On the other hand, the mechanochemical solid-state reaction was found to be the most suitable for this purpose. Thus, when the solid-state reaction was conducted for Cgo in the presence of one equivalent or less of KCN under the HSVM conditions for 30 min, a clean reaction took place to give the [2-1-2] fullerene dimer C120 (3) in 30% yield while 70% of Cgo was recovered unchanged (Scheme 2) [20]. It is to be noted that no cyanated fullerene such as 4 was obtained in comparison to the result of a liquid-phase reaction in o-dichloroben-zene (ODCB)-DMF [21]. This is apparently ascribed to the difference in reactivity of the initially formed cyanated Cgo anion with or without solvation. 

A wide variety of instrumental techniques, including X-ray diffraction, thermal analysis, electron microscopy, MAS-NMR and infrared spectroscopy, have been employed at different levels of complexity to investigate the effects of mechanochemical treatment on kaolin. Unfortunately, vibrational spectroscopy has only been used at a superficial level in the study of milled kaolin despite the considerable contribution that it has made to the understanding of the structure and reactivity of kaolin itself. 

Experiments were also performed with the aim of polymerizing a mixture of two monomers (69). The reaction rate and the composition of the graft copolymer conform to the rules of mechanochemical synthesis and radical copolymerization. If the two monomers have almost equal reactivities, the composition of the copolymer is approximately that of the initial monomer mixture (Fig. 20). The... 

This point of view concerning the mechanism of mechanochemical destruction of macromolecular compounds is based on two factors. One is the gradual character of this process, as reported by us earlier (JO). The other factor is the increase in potential energy and, consequently, the chemical reactivity of polymer systems that are placed in a stressed state mechanically. 

To enhance reactivity in ceramic reactions, intimate mixtures of small particles are preferred. Vigorous grinding, however, does not only reduce the particle size. Using high energy mills, considerable local pressures and temperatures may be achieved. So-called mechanochemical reactions are very rare with fluorides ... 

In solid state chemistry, a special term soft chemistry was proposed to describe the methods based on preliminary synthesis of intermediate compounds which are further used to prepare final products [4]. One of the authors of this monograph has introduced the term soft mechanochemistry for mechanochemical reactions with the participation of highly reactive compounds [30]. They include the reactions with the participation of compounds containing oxygen-hydrogen groups as well as other relatively unstable compounds such as peroxides, nitrates, metal carbonates and other reactive compounds. 

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