Polyethylene polymethylene

Polymers with Tg/Tm ratios below 0.5 are highly symmetrical and have short repeating units consisting of one or two main-chain atoms each, carrying substituents consisting of only a single atom (polymethylene, polyethylene, polytetrafluoroethylene, polymethylene oxide). They are markedly crystalline. 

Polymer electrolytes are used in lithium ion rechargeable batteries. Pure polymer electrolyte systems include polyethylene oxide (PEO), polymethylene-polyethylene oxide (MPEG), or polyphosphazenes. Chlorinated PVC blended with a terpoly-mer comprising vinylidene chloride/acrylonitrile/methyl methacrylate can make a good polymer electrolyte. Rechargeable lithium ion cells use solid polymer electrolytes. Plasticized polymer electrolytes are safer than liquid electrolytes because of a reduced amount of volatiles and flammables. The polymer membrane can condnct lithinm ions. The polymer membrane acts as both the separator and electrolyte [7],... 

Chemically Modified Waxes. Hydrocarbon waxes of the microcrystaHine, polyethylene, and polymethylene classes are chemically modified to meet specific market needs. In the vast majority of cases, the first step is air oxidation of the wax with or without catalysts (11). The product has an acid number usuaHy no higher than 30 and a saponification number usuaHy no lower than 25. An alternative step is the reaction of the wax with a polycarboxyHc acid, eg, maleic, at high temperature (12). Through its carboxyl groups, the oxidised wax can be further modified in such reactions as saponification or esterification. Oxidised wax is easily emulsified in water through the use of surfactants or simple soaps, and is widely used in many coating and poHsh appHcations. 

Since 1900 other methods have been devised for producing polymethylene , including the use of boron trifluoride-diethyl ether catalysts at 0°C. Some of these methods give unbranched linear polymers, often of very high molecular weight, which are useful for comparing commercial polyethylenes which have molecules that are branched to varying extents. 

With all six series of polyester illustrated in Figure 25.14, as the number of methylene groups in the repeating unit increases so the polymer becomes more like a linear polyethylene (polymethylene). Thus the melting points for five of the six classes are seen to converge towards that of the melting point of polymethylene. In the ca.se of the sixth class, the poly(alkylene adipates), there would appear no reason to believe that additional data on other specific members of the class would not lead to a similar conclusion. 

The y relaxation takes place at the lowest temperature, overlaps with the )3 relaxation (Fig. 15), and coincides in location and activation energy with the typical y relaxation of polyethylene [35,36], and also of polyethers [37], and polyesters [38] with three or more consecutive methylene units. It appears, for 3 Hz and tan6 basis, at - 120°C (P7MB) and - 126°C (P8MB), and its location and activation energy (35-45 kJ mol ) agree with the values of a similar relaxation associated with kink motions of polymethylenic sequences. 

The donor-acceptor distance may not be unique, especially when the donor and acceptor are linked by a flexible chain (e.g. end-labeled oligomers of polymethylene or polyethylene oxide, oligopeptides, oligonucleotides, polymer chains). 

Linear polyethylene can further also be considered as polymethylene. Althoguh first prepared by the thermal decomposition of diazomethane,243 244 Meerwein should be credited to have prepared it by catalytic polymerization of diazomethane effected by boron compounds (esters, halides, alkyls)245-247 taking place with concomitant dediazotation ... 

Willbourn, A. H. Polymethylene and the structure of polyethylene study of short-chain branching, its nature and effects. J. Polymer Sci. 34, 569—597 (1959). 

Considerable confusion exists in the literature concerning the real glass transition temperature of polymethylene, i.e. of ideal linear polyethylene. Values between 140 and 340 K have been reported (see Boyer, 1973,1975). In agreement with Boyer we are convinced, for a variety of reasons (see Boyer, 1973), that the correct Tg of amorphous polymethylene is 195 10 K. This gives for the basic contribution of -CH2- to Yg ... 

The most well-known member of this class is the polyether, polyethylene oxide, whose complexes with lithium perchlorate have been used commercially in lithium batteries.60-62 The good solvating power of polyethylene oxide is attributed to an optimal spacing of the electron-donating ether oxygens along a flexible backbone that allows multiple contacts between the polymer backbone and cations. When this distance is decreased, as in polymethylene oxide, chain flexibility is greatly reduced when it is increased, as in 1,3-polypropylene oxide, the distance between... 

Polymers are usually named according to their source, and the generic term is polymonomer whether or not the monomer is real. Thus we have polystyrene (1-1) and poly(vinyl alcohol) (1-7). Similarly, polyethylene is written as 1-3 although the representation TCH2)-2/i and the corresponding name polymethylene could have been chosen equally well to reflect the nature of the repealing unit. 

Polyethylene oxide (PEO) is an uncharged polymer that has a high solubility in water, especially when compared to its analogues polymethylene oxide (PMO) and pol)T)ropylene oxide (PPO) which are essentially insoluble in water. PEO solutions... 

Work of other researchers portended the discovery of polyethylene. For example, in 1898, Flans von Pechman produced a composition he called "polymethylene" by decomposition of diazomethane. "Polymethylene" was also produced by other... 

The polymer produced in eq 1.1 is known as polyethylene and, less commonly, as polymethylene, polyethene or polythene. (In the late 1960s, "polythene" became part of popular culture when the Beatles released "Polythene Pam.") Polyethylene is the lUPAC recommended name for homopolymer. As we shall see, however, many important ethylene-containing polymers are copolymers. Nomenclatures for various types of polyethylene are addressed in section 1.3. Though some have suggested that its name implies the presence of unsaturated carbon atoms, there are in fact few C=C bonds in polyethylene, usually less than 2 per thousand carbon atoms and these occur primarily as vinyl or vinylidene end groups. 

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