Polyethylene solution chemistry

Sample. This source places no restrictions on target material. Clusters of metals, produced. For example, polyethylene and alumina have been studied as well as refractory metals like tungsten and niobium. Molecular solids, liquids, and solutions could also be used. However the complexity of the vaporization process and plasma chemistry makes for even more complex mixtures in the gas phase. To date the transition metals(1-3) and early members of group 13 (IIIA) and 14 (IVA)( 11-16) have been the most actively studied. 

Polyethylene oxide) associates in solution with certain electrolytes (48—52). For example, high molecular weight species of poly(ethylene oxide) readily dissolve in methanol that contains 0.5 wt % KI, although the resin does not remain in methanol solution at room temperature. This salting-in effect has been attributed to ion binding, which prevents coagulation in the nonsolvent. Complexes with electrolytes, in particular lithium salts, have received widespread attention on account of the potential for using these materials in a polymeric battery. The performance of solid electrolytes based on poly(ethylene oxide) in terms of ion transport and conductivity has been discussed (53—58). The use of complexes of poly(ethylene oxide) in analytical chemistry has also been reviewed (59). 

The recipe for success was to select the right polymer. If polyethylene glycol [PEG or more correctly poly(oxyethylene)] was used, the problems associated with solid phase variation, namely those concerning reactivity and diffusion, were overcome, and conditions typical of chemistry in solution could be restored at the same time. Additionally, the operative advan-... 

The ethylene chemistry of isolable Cp2Ti(CH3)(L) complexes is similar to that of the Zr systems. Complexes with relatively labile ligands (L = THF, Et20, EtOPh) exhibit low polymerization activity in CH2CI2 solution. For the THF complex, Taube reported an activity of about 3 g polyethylene/(mmol Ti-atm-hour) (CH2CI2 solution, 25 °C, 1 atm) (52). The corresponding pyridine, RCN, and PR3 complexes, which are less labile, are inactive under these conditions (39). Surprisingly, the penta-methylcyclopentadienyl systems Cp 2Ti(CH3)(L) (L = THF, THT) do... 

The laser vaporization approach allows the use of even the most refractory target materials. The source configuration used in Fig. 1 involves a target rod that is rotated and translated in a continuous screw motion to expose fresh metal to the laser beam. This has been found necessary to provide acceptable pulse-to-pulse reproducibility. Target rods of refractory metals, semiconductors, carbon, polyethylene, alumina, and alloys have all been vaporized successfully to make clusters in many laboratories. For some materials a disk target is preferred due to the ease in sample preparation. Molecular solids, liquids, and solutions could also be used, though care must be taken to consider the additional complex plasma chemistry one is likely to encounter. 

Curran has developed the chemistry of tris[2-(perfluorohexyl)ethyl]tin hydride (see Section 5.4), again with the aim of making it easy to separate the organotin byproduct.67 The polar polyethylene oxide groups of the hydrides 22-8 and 22-9 make it possible to carry out radical reactions in aqueous solution.68-69... 

Potassium hexafluorophosphate [17084-13-8] M 184.1, pK 0.5, pK 5.12 (for fluoro-phosphoric acid H2PO3F). Crystallise it from alkaline aqueous solution, using polyethylene vessels, ot from 95% EtOH, and dry it in a vacuum desiccator over KOH. [Kloditz Z Anorg Allgem Chem 284 144 1956, Kwasnik in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 196 7965.]... 

We present here some aspects of the surface chemistry and some explanatory models for vrater-polymer and related Interfaces. The term "poljrmer" will be taken to mean an essentially organic material, of sufficiently high molecular weight and (or) sufficiently cross-linked that a stiff (as opposed to fluid) phase is Involved. The material Is Insoluble In water, so that the term "water-polymer" Interface refers to what Is macroscopIcally an ordinary phase boundary. Typical polymers In the present context will be polytetrafluorethylene (PTFE), and polyethylene (PE). Solutions of macromolecules are thus not considered, nor is the related topic of so-called hydrophobic bonding, although some of what Is discussed here is relevant to that subject. 

Time resolved spectroscopy has developed assignments of intermediate species in radiation chemistry as revealed in the other sections. However, because solid polymers are less transparent, the works obtained so far seem to be limited mainly to polymer solution systems or liquid model-compounds. The lifetime of intermediates depends on LET the fluorescence lifetime of n-dodecane is shorter for higher LET radiation [83], which was studied as liquid model compounds for polyethylene. The observation is attributed to scavenging upon encountering of intermediates. Light emission from excimers of solid polystyrene has constant lifetime irrespective to LET [84], whereas polystyrene... 

The active species for the PBI complexes is not as well characterized as in the nickel and palladium systems. It is assumed to be a cationic alkyl complex formed by reaction of the dihalo precatalyst with a cocatalyst such as methylaluminoxane (MAO). The resulting active species polymerizes ethylene at unusually high rates to form linear high-density polyethylene. Even at ethylene pressures as low as 1 atm, the polymerization is extremely exothermic and the crystalline polymer product rapidly precipitates from solution. Computational chemistry is proving to be of utility in understanding the mechanistic aspects of this chemistry. - Lower barriers to insertion, relative to the nickel a-diimine complexes, support the higher activity. 

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