Polyethylene oxide layers

Phyllosilicate Polyethylene oxide layered solid electrolyte, ion-selective materials 72... 

When the surface is not polymer-saturated, adsorbed chains have a flatter appearance. The thickness of the polyethylene oxide layer adsorbed on silica particles is about 6 times smaller at half-saturation than at saturation [89]. Under such conditions, a few chains can bridge several particles and cause flocculation of the colloid [81]. 

In an example of the construction of such a device, thin films of these materials are deposited on OTEs that are separated by a layer of a transparent ionic conductor such as KCF3SO3 in polyethylene oxide).125 The films can be colored simultaneously (giving deep blue) when a sufficient voltage is applied between them such that the WO3 electrode is the cathode and the PB electrode the anode. Conversely, the colored films can be bleached to transparency when the polarity is reversed, returning the ECD to a transparent state. 

Several experimental parameters have been used to describe the conformation of a polymer adsorbed at the solid-solution interface these include the thickness of the adsorbed layer (photon correlation spectroscopy(J ) (p.c.s.), small angle neutron scattering (2) (s.a.n.s.), ellipsometry (3) and force-distance measurements between adsorbed layers (A), and the surface bound fraction (e.s.r. (5), n.m.r. ( 6), calorimetry (7) and i.r. (8)). However, it is very difficult to describe the adsorbed layer with a single parameter and ideally the segment density profile of the adsorbed chain is required. Recently s.a.n.s. (9) has been used to obtain segment density profiles for polyethylene oxide (PEO) and partially hydrolysed polyvinyl alcohol adsorbed on polystyrene latex. For PEO, two types of system were examined one where the chains were terminally-anchored and the other where the polymer was physically adsorbed from solution. The profiles for these two... 

Citrate-capped Au NPs have been coated with a layer composed of the double hydrophilic block copolymer polyethylene oxide)-block-poly(2-(dimethylamino)eth-yl methacrylate)-SH (PEO-b-PDMA-SH) leading to core-shell, almost spherical, Au NPs of about 18 nm. The shell cross-linking of these hybrid Au NPs gives rise to high colloidal stability [122]. 

The block-polymers containing a middle block of polystyrene and two blocks of polyethylene oxide have some unusual properties. They are soluble in methyl ethyl ketone and cannot be precipitated from this solvent by methanol. Addition of water produces a slight cloudiness but still no precipitation although the block polymer is not soluble in pure water. The polymer is also soluble in benzene, but addition of water to this solution causes its precipitation. On the other hand, neither homopolystyrene nor homo-polyethylene oxide or their mixtures are precipitated from benzene solution by addition of water. This strange behaviour is explained by Richards and Szwarc (45) in terms of hydrogen bonding which depends on the chemical potential of water in the aqueous layer and therefore also in the benzene solution. 

The gels can incorporate even polymers such as, for example, water-soluble polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), and polypropyl-eneglycol (PPG). For the PE0/V205 system the interlayer broadening achieved 13.2 A, which corresponds to more probable placement of the polymer molecules along the layers [1373] (Fig. 11.1 b). 

Examples of known phosphazene polymer blends are those in which phosphazenes with methylamino, trifluoroethoxy, phenoxy, or oligo-ethyleneoxy side groups form blends with poly(vinyl chloride), polystyrene, poly(methyl methacrylate), or polyethylene oxide).97 100 IPNs have been produced from [NP(OCH2CH2OCH2CH2OCH3)2] (MEEP) and poly(methyl methacrylate).101-103 In addition, a special type of IPN has been reported in which a water-soluble polyphosphazene such as MEEP forms an IPN with a silicate or titanate network generated by hydrolysis of tetraethoxysilane or tetraalkoxytitanane.104 These materials are polyphosphazene/ceramic composites, which have been described as suitable materials for the preparation of antistatic layers in the manufacture of photographic film. 

Solid hydrocarbon soils can be rapidly removed from the surface of a ZnSe IRE by alkyl polyethylene oxide) surfactants. The removal mechanism involves penetration of a small amount of the surfactant into the hydrocarbon layer, which causes an increase in methylene chain defects in the soil, and displacement of solid soil from the substrate. Solubilization of a large fraction of the solid soil is not required. 

The second repulsive energy (referred to as steric repulsion) is produced by the presence of adsorbed surfactant layers of nonionic surfactants, such as alcohol ethoxylates or A-B, A-B-A block, or BA graft copolymers, where B is the anchor chain and A is the stabilizing chain [mostly based on polyethylene oxide (PEO) for aqueous systems]. When two droplets or particles with adsorbed PEO chains of thickness 5 approach a separation distance h such that h < 28, repulsion occurs as a result of two main effects. The first arises as a result of the unfavorable mixing of the PEO chains, when these are in good solvent conditions. This is referred to as Gm x and is given by the following expression ... 

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 ... 

In order to test the model used here, calculated values of the limiting free polymer concentration 0 at which phase separation occurs are compared with the experimental data [6] on the aqueous dispersions of polystyrene latex particles with adsorbed polyethylene oxide and with polyethylene oxide as the free polymer. Since no information is available regarding the thickness of the adsorbed layer, the values used by Vincent et al. [6] in their theoretical calculations are adopted. Table 1 compares the experimental values of the limiting volume fraction of the free polymer with our calculated values for two different molecular weights of the free polymer. The simple model used here gives reasonably good agreement with the experimental values. 

Polyethylene oxide). This ether-rich polymer (PEO) apparently forms hydrogen bonds with silanol groups, with concomitant adsorption of a PEO layer at silica surfaces. In the case of CZE, the fused silica capillaries are pretreated with 0.1 M NaOH and 0.1 M SDS at the beginning of each day. The typical coating protocol is to flush the capillary with 1.0 M HC1, followed by a solution of 0.2% PEO, then washing with an electrophoretic buffer. The coating process has to be repeated before each run. The EOF is reduced by 60-70%, and the columns thus treated work well for basic proteins. 

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