Monomeric ethylene

Upon thermal destruction of polyethylene the chain transfer reactions are predominant, but depolymerization proceeds to a much lesser extent. As a result, the products of destruction represent the polymeric chain fragments of different length, and monomeric ethylene is formed to the extent of 1-3% by mass of polyethylene. C—C bonds in polypropylene are less strong than in polyethylene because of the fact that each second carbon atom in the main chain is the tertiary one. 

The oligomerization of the ethylene is performed at 80-120°C and at a pressure of 70-140 bar. A solvent like 1,4-butanediol is used, in which only the catalyst and the monomeric ethylene are soluble but not the formed higher molecular weight olefins. The oligomerization of the ethylene in such a two-phase systems enables the separation of the homogeneous catalyst from the reaction product by a simple phase separation. 

I hope the reader will not be too disappointed that he had to accompany me through some fields of small-molecule or at the most middle-sized molecule chemistry and has not up to here read a word about macromole-cular chemistry, in which according to a quite general opinion, well known to me, I am said to be a special expert. As a matter of fact, except for my former activity in the field of polybutadiene and polystyrene chemistry which touched the problems later on referred to as living polymers, I was never closely connected with macromolecular chemistry. But my own life contained some surprises, and I believe the most astonishing event was my sudden confrontation with macromolecules in consequence of an experiment which led from monomeric ethylene to its lowest possible polymer, ... 

Presence of impurities in excipients can have a dramatic influence on the safety, efficacy or stability of the drug product. Monomers or metal catalysts used during a polymerization process are toxic and can also destabilize the drug product if present in trace amounts. Due to safety concerns, the limit of vinyl chloride (monomer) in polyvinyl pyrrolidone is nmt 10 ppm, and for hydrazine (a side product of polymerization reaction) nmt 1 ppm. Monomeric ethylene oxide is highly toxic and can be present in ethoxylated excipients such as PEGs, ethoxylated fatty acids, etc. 

Scission of these chain side radicals can result In radicals terminated by sequences of methylene groups which should be capable of liberating a proportion of monomeric ethylene by depoly-merlzatlon (reactions 6 and 8). This Is very much less probable if radicals are initially formed by main chain scission as in the thermal reaction. 

An interesting method for producing plastic microspheres is disclosed by Bayer AG (13). The microspheres consist of vinyl chloride-ethylene copolymers. This method involves the use of the difference of monomer reactivity between vinyl chloride and ethylene. Upon radical polymerization of the two monomers at 50°C, vinyl chloride reacts faster than does ethylene, and unreacted monomeric ethylene then remains in the resulting copolymer jn-oduced by the pearl polymerization. The monomer can then act as the blowing agent. 

In order to detect radical ions, mass spectrometry, electron spectroscopy, and ESR are used in combination with optical bleaching. For example, according to mass spectrometric data, ethylene forms a dimer particle, C4H8, as a result of a primary ion-molecular reaction. This particle reacting with monomeric ethylene produces growing chains up to C14 with a radical-ion active centre ... 

In the contact region of C50 and PEG 200, the only enantiotropic liquid crystalline phase appearing is a N phase, as seen in Fig. 5.9. Upon cooling, a monotropic lamellar L phase is formed. In contrast to the sample with monomeric ethylene glycol, the lamellar L phase which forms with PEG 200 is only stable in a range of a few Kelvin but in a quite broad concentration range. 

TEGEWA, Determination of monomeric ethylene oxide in pharmaceutical raw materials,... 

Plasticizers. Monomeric (mol wt 250—450) plasticizers (qv) are predominantiy phthalate, adipate, sebacate, phosphate, or trimeUitate esters. Organic phthalate esters like dioctyl phthalate (DOP) are by far the most common plasticizers in flexible PVC. Phthalates are good general-purpose plasticizers which impart good physical and low temperature properties but lack permanence in hot or extractive service conditions and are therefore sometimes called migratory plasticizers. Polymeric plasticizers (mol wt up to 5000 or more) offer an improvement in nonmigratory permanence at a sacrifice in cost, low temperature properties, and processibiHty examples are ethylene vinyl acetate or nitrile polymers. 

When equal amounts of solutions of poly(ethylene oxide) and poly(acryhc acid) ate mixed, a precipitate, which appears to be an association product of the two polymers, forms immediately. This association reaction is influenced by hydrogen-ion concentration. Below ca pH 4, the complex precipitates from solution. Above ca pH 12, precipitation also occurs, but probably only poly(ethylene oxide) precipitates. If solution viscosity is used as an indication of the degree of association, it appears that association becomes mote pronounced as the pH is reduced toward a lower limit of about four. The highest yield of insoluble complex usually occurs at an equimolar ratio of ether and carboxyl groups. Studies of the poly(ethylene oxide)—poly(methacryhc acid) complexes indicate a stoichiometric ratio of three monomeric units of ethylene oxide for each methacrylic acid unit. 

Addition polymers are formed by the reaction of the monomeric units without the elimination of atoms. The monomer is usually an unsaturated organic compound such as ethylene, H2C=CHs, which in the presence of a suitable catalyst will undergo an addition reaction to form a long chain molecule such as polyethylene. A general equation for the first stage of such a process is... 

A dispersant that can be used in drilling fluids, spacer fluids, cement slurries, completion fluids, and mixtures of drilling fluids and cement slurries controls the rheologic properties of and enhances the filtrate control in these fluids. The dispersant consists of polymers derived from monomeric residues, including low-molecular-weight olefins that may be sulfonated or phosphonated, unsaturated dicarboxylic acids, ethylenically unsaturated anhydrides, unsaturated aliphatic monocarboxylic acids, vinyl alcohols and diols, and sulfonated or phosphonated styrene. The sulfonic acid, phosphonic acid, and carboxylic acid groups on the polymers may be present in neutralized form as alkali metal or ammonium salts [192,193]. 

The effect of donors on the catalyst activity can be explained by assuming that the dimeric complex is not an active catalyst (Cramer s kinetics indicate a monomeric Rh species as active catalyst see Section II,B,2) and that 14 with a free coordination site for ethylene is the active catalyst, while 15 with both coordination sites occupied by donors is catalytically inactive. When D is a weak donor, such as ketone or ether (see Fig. 5d), the reaction rate increases, slowly reaching a maximum and leveling off at the maximum as the concentration of the donor is increased. It can be speculated that these donors interact with the catalyst only to the extent that they break up the dimer 8 to form 14, but that... 

The procedure described above is essentially that of Thomas.2 Nor-bomylene has also been prepared by the additon of ethylene to monomeric cyclopentadiene 3 [Org. Syntheses, 32, 41 (1952)], by dehydration of j3-norbomeol with phosphorus pentoxide,4 and by dehydrohalogena-tion of norbornyl chloride or bromide using quinoline.4-6... 

Treatment of 45 with 5 mol% la under an atmosphere of ethylene leads to 50% conversion to 41 (12 h 400 MHz H NMR analysis). Therefore, in the presence of ethylene, even if dimer is formed, it can be readily converted to the monomeric form with reasonable efficiency. 

AE and AP surfactants are synthesised by polymerisation of monomeric or short chain oligomeric glycol moieties. If mixtures of ethylene and propylene glycols, however, were applied for the synthesis, so called EO/PO block polymers in the form of complex mixtures with the general formula R-0-(E0)m-(P0) -H and the structure as shown with their... 

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