Polymerization atomic

The constituents are arranged in an alternating way, Mes/Cr/Mes/Cr/Mes. In general, liquid phase addition reactions occur at a metal site, pre-formed in a support medium that contains arene functionalities (48). Free arene substituents and organometallic tt-complexes can therefore trap a diffusing metal atom. Under well-defined conditions, such reactions are favored over competing metal atom polymerizations. 

Changing Catalytic Selectivity Atom by Atom Polymerization of Acetylene on Palladium Nanocatalysts... 

Table V. No. of C Atoms Polymerization of Butadiene (2)a Polymer Produced ...

Because of the contribution of atomic polymerization, the plasma polymer of styrene in its most practical and useful form is distinctly different from polystyrene. This is exactly why plasma polymers can be used to improve the wear resistance of other polymers. If the plasma polymerization of styrene did produce a conventional polystyrene, one could not expect any improvement in the wear resistance of polystyrene by using plasma polymerization. Because the plasma polymer of styrene is not polystyrene, the deposition of the plasma polymer of styrene on the surface of polystyrene can produce a remarkable improvement. 

Styrene to poly(styrene) but an atomic polymerization in which some of the elements or groups of the monomer are not incorporated into the polymer. 

In the case of silicon alkoxides, hydrolysis occurs by the nucleophilic attack of the oxygen contained in water on the silicon atom and is most rapid and complete when acid (e.g. HCl, CH3COOH, HF,. ..) or basic (e.g. NH3, KOH, amines,. ..) catalysts are employed. Under acidic conditions, it is likely that an alkoxide group is protonated in a rapid first step. Electron density is withdrawn from silicon, making it more electrophilic and thus more susceptible to be attacked by water. Under basic conditions it is likely that water dissociates to produce nucleophilic hydroxyl anions in a rapid first step. The hydroxyl anion then attacks the silicon atom. Polymerization... 

Oxidative coupling n. A process defined as a reaction of oxygen with active hydrogen atoms from different molecules, producing water and a dimerized molecule. If the hydrogen-yielding substance has two active hydrogen atoms polymerization results. This process is used in the polymerization of phenols, particular polyphenylene oxide. 

Other compounds of vinyl type that are used for polymers include acrylonitrile (vinyl cyanide), H2C=CH(CN), and styrene, H2C=CH(C H3). Vinyl compounds are all polymerized by addition process. Tetrafluoroethylene, F C=CF, in which all the hydrogen atoms of ethylene are replaced by fluorine atoms, polymerizes similarly to form a polymer of unique character, teflon. 

Amphiphilic molecules [11-14] consist of mutually incompatible components. Since these components are chemically joined, complete segregation is impossible. It is replaced by various forms of microphase separation. These involve formation of segregated domains such that at least one of their dimensions is comparable to the molecular size. The domains are formed by spontaneous, thermodynamically driven aggregation of the amphiphiles. The process is thus often referred to as self-assembly. The resulting structures, micelles, lamellae, etc. can also form ordered mesophases. The microphase separation can take place in a solvent that selectively solubilizes one component or in a melt of neat amphiphiles. These characteristics are common to both polymeric and monomeric, low molecular weight amphiphiles. For the purposes of our discussion monomeric amphiphiles are defined, somewhat arbitrarily, as those consisting of 10 atoms. Polymeric amphiphiles, on the other hand, can incorporate 10 -10 atoms. The consequences of this difference are the topic of this article. 

Strictly speaking, the ususal process of polymerization is not the same as the process that occurs in glow discharge. In this context, polymer formation in a plasma state takes place via a "nonpolymerizing" process. Thus, polymer formation of this type may be characterized as elemental or atomic polymerization in contrast to molecular polymerization, which describes the conventional process. The following discussion may illustrate the atomic nature of polymer formation in a plasma state. 

There is no clear-cut answer to whether atomic polymerization theory or precursor theory explains the actual process of polymer formation in glow discharge better, because there is no direct evidence to prove or disprove either. 

All experimental data in glow discharge polymerization can be interpreted only as circumstantial evidence so far as the mechanism of pol3nner formation is concerned. Therefore, the following discussion presented to support the concept of atomic polymerization is not intended to disprove any... 

Characteristics of atomic polymerization are directly seen in the incorporation of gases or vapors, such as N2,... 

The aspect of atomic polymerization can be clearly seen in the molecular structural difference of monomers and polymers, but with the glow discharge polymers of hydrocarbons, without appropriate analytical tools, it is difficult to... 

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