Linear polyethers

Linear polyethers derived from three or more molecules of aliphatic dihydroxy compounds, particularly when the chain length exceeds ten units, are most conveniently named by open-chain replacement nomenclature. For example, CH3CH2—O—CH2CH2—O—CH2CH3 could be 3,6-dioxaoctane or (2-ethoxy)ethoxyethane. 

The formation of complexes of 2 1 stoichiometry is not restricted to cyclic ligands it has also been observed with linear polyethers (Kodama and Kimura, 1976 Tiimmler et al., 1977). 

Rates of decomplexation (kJ2) of cation complexes can also be determined by nmr spectroscopy on the cation. Rates of complex formation are then calculated from kn and the binding constant. The results for several ligands, cations, and solvents are given in Table 20. Despite the wide variations, the rates of complex formation are all in the range 2 x 107 to 8 x 10 M 1 s 1. In contrast, rates of decomplexation for crown-ether complexes span a much broader range 6.1 x 102 to 2 x 105 s 1. Comparison of crown-ether data with data for [2.2.2]-cryptand [37] and the linear polyether [92] also shows that the... 

Lee and Chang (1978) have compared the ability of linear polyethers, crown ethers, and quaternary ammonium compounds to catalyse oxidations with KMn04 under liquid-liquid and liquid-solid conditions. In the presence of acetic acid as a scavenger for the KOH produced, the products of olefin oxidation were carboxylic acids, diones, diols and ketols. The three different classes of catalysts exhibited about the same activity in liquid-solid systems. 

So far only a few quantitative data on the thermodynamic stability of arenediazonium salts and crown ethers have been reported. Bartsch et al. (1976) calculated the value of the association constant of the complex of 18-crown-6 and 4-t-butylbenzenediazonium tetrafluoroborate from kinetic data on the thermal decomposition of the complex, Kt = 1.56 x 105 1 mol-1 in 1,2-dichloroethane at 50°C. Compared with the corresponding linear polyether this is at least a factor of 30 higher (Bartsch and Juri, 1979). 

Quaternary onium salts were the first phase-transfer catalysts used subsequently, a number of compounds (linear polyethers, polypodands, crown-ethers, cryptands, cage-compounds, etc.) were found effective for the anion activation in two-phase systems. These structurally different systems must satisfy at least two fundamental conditions in order to behave as phase-transfer catalysts i) solubility in the organic phase ii) steric hindrance around the cationic center leading to a good cation-anion separation within the ion-pair. 

Eponol Linear polyether resins Shell Chemical... 

Polyethers 101 derived from 1 were mentioned in a patent describing the synthesis and properties of epoxy resins, and linear polyethers were prepared from free 1, which was reacted with a,co-bischloroalkanes or 1,6-dibromohexane [17]. 

Polymerization is frequently observed as a side reaction in acid-catalyzed reactions, and under appropriate conditions many oxetanes can be quantitatively transformed into high molecular weight linear polyethers with useful properties. Polymerization is very general for oxetanes and is closely related to Lewis acid-catalyzed polymerization of oxiranes, THF and oxepane, but oxetanes generally polymerize much more rapidly than THF and oxepane and at a rate similar to oxiranes (72MI51300). 

Bailey, F.E., Jr., France, H.G. Rates of polymerization and relative copolymerization rates of some epoxides in the formation of linear polyethers. 

Our next case history takes what we have learnt about donor-acceptor interactions between arene building blocks in interlocked molecules and exploits that knowledge base in a more conventional intramolecular arena. The self-complexing compound 164+ (Figure 10) incorporates [11] a linear polyether thread intercepted by a DNP ring system, which is co-... 

A more practical way to make linear polyethers is by polymerization of epoxides. Each time an epoxide is opened by a nucleophile, it releases a nucleophilic oxyanion that can attack another epoxide, and so on. The whole process can be initiated by just a catalytic amount of a nucleophile such as an alkoxide or an amine. 

Recent experimental data [28] indeed show that a weak interface can be created by lowering the surface energy with an fluorocarbon elastomer coating. On such a weakly adsorbing die wall, a macroscopic slip occurs in linear polyeth-ylenes during capillary die extrusion. However, the same surface fails to produce any observable wall slip at low stresses that can be reliably generated in a parallel-plate flow cell. This contrast emphasizes that massive polymer desorption and interfacial slip occur only beyond a critical wall stress. 

The above drawbacks of the linear polyfunctional macromolecular supports are to a greater extent overcome by the use of appropriate polyethers as soluble supports for biopolymer synthesis. Absence of any steric effect, equivalence of functional groups and compatibility with the biopolymers being synthesized can be expected from polyethyleneglycols, which are linear polyethers with two hydroxy groups at the chain ends (21). 

The linear polyethers are model compounds to show the effect of the insertion of one oxygen atom at different positions into the polyethylene -CH2-CH -repetitive unit. What will be the influence on the polymer XPS valence band spectrum, compared to the one of polyethylene (Figure 2) Our study was conducted on three materials poly(methylene oxide) or PMO, poly(ethylene oxide) or PEO, and poly(tetramethylene oxide) or PTMO, that are... 

Figure 10. XPS valence band spectra of the linear polyethers (I) polyfmethylene oxide), (2) polyfethylene oxide), (4) poly(tetramethylene oxide) (A).

Preliminary investigations suggested that it would be possible to form a related poly-pseudorotaxane built up from a linear component incorporating linked linear polyether strings. Thus, reaction of the linear component incorporating three hydroquinone residues with methylenebis(4-phenylisocyanate) yielded the... 

Linear polystyrene can be functionalized by various methods . The functional group capacity in these polymers diould not be too high otherwise, steric complications may arise. Poly(ethylene ycol) has been found to be most suitable for liquid-phase synthesis. This linear polyether and the block copolymers with functional groups at defined distances are chemically stable and soluble in a large number of solvents including water and can be precipitated selectively. Partially hydrolyzed poly(vinylpyrrolidone) and its copolymers with vinyl acetate were successfully applied in peptide synthesis. Poly(acrylic acid), poly(vinyl alcdiol), and poly-(ethylenimine) are less suitable for the sequential type synthesis because of the... 

The above drawbacks are to a greater extent overcome when using linear polyethers as soluble supports for the sequential type synthesis. The presence of a hydrophilic and hydrophobic moiety per monomer unit lends this class of polymers... 

Comparative studies between crown ethers and the noncyclic glymes (linear polyethers) suggest that glyme complexes are favored — the chelate effect is thus more important than the macro-cyclic effect. The more flexible glymes may accommodate water molecules and other small ligands (e.g., anions) more easily. Solubility effects may play a part too " ... 

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