Dielectric ethylene

The equimolar copolymer of ethylene and tetrafluoroethylene is isomeric with poly(vinyhdene fluoride) but has a higher melting point (16,17) and a lower dielectric loss (18,19) (see Fluorine compounds, organic-poly(VINYLIDENE fluoride)). A copolymer with the degree of alternation of about 0.88 was used to study the stmcture (20). Its unit cell was determined by x-ray diffraction. Despite irregularities in the chain stmcture and low crystallinity, a unit cell and stmcture was derived that gave a calculated crystalline density of 1.9 g/cm. The unit cell is befleved to be orthorhombic or monoclinic (a = 0.96 nm, b = 0.925 nm, c = 0.50 nm 7 = 96%. 

The importance of the solvent, in many cases an excess of the quatemizing reagent, in the formation of heterocyclic salts was recognized early. The function of dielectric constants and other more detailed influences on quatemization are dealt with in Section VI, but a consideration of the subject from a preparative standpoint is presented here. Methanol and ethanol are used frequently as solvents, and acetone,chloroform, acetonitrile, nitrobenzene, and dimethyl-formamide have been used successfully. The last two solvents were among those considered by Coleman and Fuoss in their search for a suitable solvent for kinetic experiments both solvents gave rise to side reactions when used for the reaction of pyridine with i-butyl bromide. Their observation with nitrobenzene is unexpected, and no other workers have reported difficulties. However, tetramethylene sulfone, 2,4-dimethylsulfolane, ethylene and propylene carbonates, and salicylaldehyde were satisfactory, giving relatively rapid reactions and clean products. Ethylene dichloride, used quite frequently for Friedel-Crafts reactions, would be expected to be a useful solvent but has only recently been used for quatemization reactions. ... 

Cohen et have also made some observations on the exchange in water-sucrose and water-ethylene glycol mixed solvents containing perchloric acid (0.106 M). Over a range of dielectric constant 68 to 88, no alteration in the exchange rate was observed. 

Linear combination of atomic orbitals (LCAO) method, 16 736 Linear condensation, in silanol polycondensation, 22 557-558 Linear congruential generator (LCG), 26 1002-1003 Linear copolymers, 7 610t Linear density, 19 742 of fibers, 11 166, 182 Linear dielectrics, 11 91 Linear elastic fracture mechanics (LEFM), 1 509-510 16 184 20 350 Linear ethoxylates, 23 537 Linear ethylene copolymers, 20 179-180 Linear-flow reactor (LFR) polymerization process, 23 394, 395, 396 Linear free energy relationship (LFER) methods, 16 753, 754 Linear higher a-olefins, 20 429 Linear internal olefins (LIOs), 17 724 Linear ion traps, 15 662 Linear kinetics, 9 612 Linear low density polyethylene (LLDPE), 10 596 17 724-725 20 179-211 24 267, 268. See also LLDPE entries a-olefin content in, 20 185-186 analytical and test methods for,... 

In the first DNMR studies of push-pull ethylenes, a strong effect of solvent polarity on the C=C barriers was noted. Thus Kende et al. (64) found AG = 18.0 kcal/mol for 46a in N,/V-dimethylformamide (dielectric constant e = 38) and 19.4 kcal/mol in Ph20 ( = 4). Similar observations have been made by many other workers, and they have been seen as a strong support for a zwitterionic transition state. Kessler et al. (140) observed reasonably linear correlations between AG for two ketene aminals and the solvent polarity parameter T (141) with variations in AG of ca. 2.5 kcal/mol over T values between 25 and 46. Similarly, Shvo et al. (78) found linear correlations between log km and the polarity parameter Z (141) for three compounds from Table 12. 

Fig. 9. Logarithm plots of the dielectric constant of water (7), methanol (1), and various aqueous-organic mixtures (2-6, Methanol-water at 80 20, 70 30,60 40, 50 50, and 40 60 v/v, respectively, and 8, ethylene glycol-water at 50 50 v/v) vs temperature. As the concentradon of the organic component increases, the dielectric constant decreases, but this effect is reversed by lowering the temperature.

Dielectric Constant (D) and Freezing Point of Ethylene Glycol—Water Mixtures"... 

Ah initio calculations to map out the gas-phase activation free energy profiles of the reactions of trimethyl phosphate (TMP) (246) with three nucleophiles, HO, MeO and F have been carried out. The calculations revealed, inter alia, a novel activation free-energy pathway for HO attack on TMP in the gas phase in which initial addition at phosphorus is followed by pseudorotation and subsequent elimination with simultaneous intramolecular proton transfer. Ah initio calculations and continuum dielectric methods have been employed to map out the lowest activation free-energy profiles for the alkaline hydrolysis of a five-membered cyclic phosphate, methyl ethylene phosphate (247), its acyclic analogue, trimethyl phosphate (246), and its six-membered ring counterpart, methyl propylene phosphate (248). The rate-limiting step for the three reactions was found to be hydroxyl ion attack at the phosphorus atom of the triester. ... 

A copolymer of ethylene and chlorotrifluoroethylene is mixed with 0.5 to 2 wt.% of boron nitride, the blend obtained is extruded at 260 to 300C, nitrogen is injected into the blend at 50 to 150 atmospheres and the pressure is lowered to produce the expanded article, which has high dielectric properties. 

Interest in cyclic olefin (co)polymers has increased dramatically over the past decade. This is because this class of polymers displays many attractive properties such as high thermal stability, high optical transparency, low dielectric constants, and low moisture absorption. Thus, these polymers can potentially be utilized in many electronic and optical applications. Although cyclic olefin (co)polymers typically include ring-opening metathesis polymers, vinyl-addition homopolymers, and vinyl-addition co-polymers with acyclic co-monomers such as ethylene, we will mainly deal with vinyl-addition homo- and co-polymers in this section. 

Catalyst stability in this system is substantially influenced by the characteristics of solvents and promoters. Indeed, the properties of solvents and promoters which improve the catalytic activity for ethylene glycol production (increased dielectric constant, greater cation complexing ability, or... 

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