Polyethylene chain

Annis B K, Noid D W, Sumpter B G, Reffner J R and Wunderlich B 1992 Application of atomic force microscopy (AFM) to a block copolymer and an extended chain polyethylene Makromol. Chem., Rapid. Commun. 13 169 Annis B K, Schwark D W, Reffner J R, Thomas E L and Wunderlich B 1992 Determination of surface morphology of diblock copolymers of styrene and butadiene by atomic force microscopy Makromol. Chem. 193 2589... 

It was noted early by Smid and his coworkers that open-chained polyethylene glycol type compounds bind alkali metals much as the crowns do, but with considerably lower binding constants. This suggested that such materials could be substituted for crown ethers in phase transfer catalytic reactions where a larger amount of the more economical material could effect the transformation just as effectively as more expensive cyclic ethers. Knbchel and coworkers demonstrated the application of open-chained crown ether equivalents in 1975 . Recently, a number of applications have been published in which simple polyethylene glycols are substituted for crowns . These include nucleophilic substitution reactions, as well as solubilization of arenediazonium cations . Glymes have also been bound into polymer backbones for use as catalysts " " . 

The reaction temperature is above the critical temperature of ethylene so that the ethylene is in gas phase. High pressures are needed for propagation reaction. Only about 6-25 per cent of ethylene is polymerised. Rest of monomer is recycled. Extensive chain transfer reactions takes place during polymerisation to yield a branched chain polyethylene. In addition to long branches, it also contains a large number of short branches of upto 5 carbon atoms produced by intra-molecular chain transfer reactions. A typical molecule of Low density polyethylene contains a short branch for about every 50 carbon atoms and one or two long branches per molecule. 

Brown, J.R., P.J.C. Chappell, Z. Mathys (1992b). Plasma surface modification of advanced organic fibers, part III. Effects on the mechanical properties of aramid/vinylester and extended chain polyethylene/ vinylester composites. J. Mater. Sci. 27. 6475-6480. 

Fig. 1.7. Representation of the energetically minimized coil shape of a short chain polyethylene ( n = 55) as obtained via mean-held calculations...

Fig. 19. Fracture surface of extended chain polyethylene crystallized at about 480 MPa pressure at 493 K (21 h) followed by slow cooling (96 % cryst.). Weight average molecular weight 24,100. Electron micrograph of a replica. Scale bar 1 micrometer. R. B. Prime, unpublished...

Some catalyst sites are apparently specific enough to close the cyclopropane ring by breaking adjacent bonds in structure (II) and (III) producing methylcyclopropane and cyclopropane. Long chain polyethylene is produced by the same mechanism postulated for 1-butene if the product remains on the catalyst and reacts repeatedly with ethylene by the following sequence. 

For the LC structure, each elementary sheet results from the superposition of two layers a layer of thickness dA formed by the solvated amorphous block (polystyrene or polybutadiene) and a layer of thickness dB formed by the crystalline and folded chains (polyethylene oxide) or polycaprolactone)265,269,271 ... 

Extended-chain polyethylene fiber became available commercially in 1984 when DSM, a Dutch firm in the Netherlands, introduced Dyneema , and Mitsui Petrochemicals in Japan announced Tekmilon . Allied Signal of the United States entered the field in 1985 when it introduced Spectra fibers. These materials are characterized by very high strength and modulus, which are achieved by the use of ultrahigh molecular weight polyethylene spun by the gel spinning method into fibers having extended-chain structures and near perfect orientation. 

The Norwegian chemist Dale found that if a primary amine is reacted with a diiodo derivative of a short-chain polyethylene glycol, such as 18, then reasonable yields of the cyclic mono-aza crown ether were obtained using Na2C03 in acetonitrile, as in the formation of the [12]-N03 ligand 19.14... 

A remarkable development in polymer science was the observation by A. J. Pen-nings that, when dilute solutions of polyethylene were cooled under conditions of continuous stirring, very fine fibres were precipitated on the stirrer. These fibres possessed a remarkable morphology consisting of a fine central core of extended chain polyethylene with an outer sheath of folded chain polymer material, so that electron microscopy revealed a beautiful shish-kebab structure. The possible significance of this result was recognised by Frank who emphasised the importance of extensional... 

Density and heat of fusion of folded chain polyethylene crystals. J. Phys. Chem. 72, 178 (1968). 

Xu Z, Holland NB, Marchant RE (2001) Conformations of short-chain polyethylene oxide) lipopolymers at the air-water interface a combined film balance and surface tension study. Langmuir 17 377-383... 

Chain scissioning of polyethylene via the alkoxy radical would yield a terminal aldehyde and shorter-chain polyethylene free radical. 

SPOCC resin is based on the cross-linking of long-chain polyethylene glycol) (PEG) terminally substituted with oxetane by cationic ring-opening polymerization. 

Table II. Production of Straight-Chain Polyethylene Waxes (6)...

Polyethylene glycol-electrolyte solutions Long-chain polyethylene glycols (PEGs molecular weight -3350... 

Czornyj G, Wunderlich B (1977) Preparationen and study of separated single crystals of extended-chain polyethylene. J. Polymer ScL, Polymer Phys. Ed. 75 1905... 

Schonfdd A, Wilke W (1972) Determination of crystallite size and lattice distortion in extended chain polyethylene and their change after oxidative degradation. Kolloid Z. Z. Polym. 250 496... 

Extended-Chain Polyethylene Fibers (ECPE) fibers are relatively recent entrants into the high-performance fibers field. Spectra ECPE, the first commercially available ECPE fiber and the first in... 

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