Polyether backbone

A new type of impression material that has a polyether backbone with urethane—acryHc end groups and that cures free-radicaUy by visible light kradiation, has been developed (244). 

Methods of detection, metabolism, and pathophysiology of the brevetoxins, PbTx-2 and PbTx-3, are summarized. Infrared spectroscopy and innovative chromatographic techniques were examined as methods for detection and structural analysis. Toxicokinetic and metabolic studies for in vivo and in vitro systems demonstrated hepatic metabolism and biliary excretion. An in vivo model of brevetoxin intoxication was developed in conscious tethered rats. Intravenous administration of toxin resulted in a precipitous decrease in body temperature and respiratory rate, as well as signs suggesting central nervous system involvement. A polyclonal antiserum against the brevetoxin polyether backbone was prepared a radioimmunoassay was developed with a sub-nanogram detection limit. This antiserum, when administered prophylactically, protected rats against the toxic effects of brevetoxin. 

Standard curves performed under our defined radioimmunoassay conditions ([ H]PbTx-3 = 1 nM, antiserum dilution = 1 2000, assay volume = 1 ml) demonstrated the ability of this antiserum to bind equally to PbTx-2 and PbTx-3, suggesting specificity for the cyclic polyether backbone region of the molecule (Figure 8). The linear portion of the curve indicated a lower detection limit of 0.2-0.5 ng in saline buffer under these conditions. Evaluation of this assay for use with biological fluids and tissue extracts is underway. 

In order to demonstrate the use of laser flash photolysis in elucidation of the MDI based polyurethane photolysis mechanism, three polyurethanes, two aryl biscarbamate models, an aryl monocarbamate model, and an aromatic amine were selected. Two of the polyurethanes are based on MDI while the third is based on TDI (mixture of 2,4 and 2,6 isomers in 80/20 ratio). The MDI based polyurethanes all have the same basic carbamate repeat unit. The MDI elastomer (MDI-PUE) is soluble in tetrahydrofuran (THF). The simple polyurethane (MDI-PU) based on MDI and 1,4-butanediol is used in the tert-butoxy abstraction reactions since it does not contain a polyether backbone. (See page 47 for structures of polymers and models.)... 

Thus, it was concluded that, combined the medium reactivity of chloromethyl group and flexible polyether-backbone, PECH is one of the most promising halogenated polymers for the developement of various new functional materials. 

In a similar way, the grafting-from technique has been applied to the synthesis of poly(chloroethylvinylether) chains by grafted PCL segments, i.e., po-ly(CEVE-g-CL) graft copolymers. Purposely cationically prepared PCEVE were partially modified by the introduction of 5-10% hydroxyl groups [79]. An equimolar reaction of the pendant hydroxyl functions with HAI/BU2 provided diisobutyl aluminum monoalkoxides dispersed along the polyether backbone. 

Several amine functionalized hyperbranched PGs have been reported as potential gene delivery systems after a proper surface group functionalization. In comparison to other dendritic structures, these scaffolds have the added advantage of being open, flexible, and possessing a polyether backbone which keeps the toxicity profile low. Different systems have been studied by post-modification of the hydroxyl groups... 

The most used polyols have a polyester or a polyether backbone. A wide variety of isocyanates are used, with toluene di-isocyanate, /w-phenylene di-isocyanate, and hexamethyl-ene di-isocyanate the most common. 

Reaction would take place on both the primary and secondary nitrogen groups, of course. The end result would be a highly crosslinked structure, yet retaining some ductility because of the flexible polyether backbone chains. 

Thin-layer chromatography (TLC) of PEG derivatives was carried out on silica gel G (Merck) in n-propanol-30% aqueous NH4OH-H2O (10 2 1), with detection by iodine vapor. This novel TLC system efficiently separated the components of the mixture of partially carboxylated PEG. The qualitative polyacrylic acid (PAA) test, carried out by treating a drop of a sample solution with a drop of 1% PAA (Aldrich, = 250000) in 1 M aqueous HCl, was used to check chromatographic fractions for the presence of PEG. Immediate appearance of a white precipitate of the PEG-PAA complex [60,61] indicated PEG this test proved to be very specific to the polyether backbone of PEG and was not influenced by end-group modifications of the polymer, molecular weight, or the presence of inorganic ions in the analyzed fractions. 

The Jeffamines brand polyoxyalkyleneamines are a part of an ever-expanding family of Industrial chemistry. They contain primary amino groups attached to the terminus of a poly ether backbone. They are thus polyether amines. The polyether backbone is based either on propylene oxide (PO), ethylene oxide (EO), or mixed EO/PO. The Jeffamines product family consists of monoamines, diamines, and triamines, which are available in a variety of molecular weights, ranging up to... 

Polyether acrylates are not a common choice of formulations for EB curable coatings. These oligomers have low to very low viscosity and often exhibit very high flexibility. Interestingly, because of the polyether backbones, they are compatible with water and can be used for water thinable formulation. 

In the 1960s Diamond Alkali marketed several polymers having a polyether backbone terminated with mercaptan groups [5,6]. Polymers of poly(oxyalkalene)polyol backbone can be esterified with thio-substituted organic acids to produce terminal mercaptan end groups. These polymers were cured similarly to conventional polysulfides, but gave generally poorer properties and were therefore withdrawn from the market. 

Since the Voranol 3010 polyol is fully PO tipped, the reactive hydroxyl group can be represented by a secondary alcohol. The unreactive polyether backbone of the polyol can be represented by the dimethyl ethers of dipropylene glycol and diethylene glycol. The diglyme represents the wt% EO incorporation into the polyol. Note the sum of the masses of the model alcohol and the two dimethyl ethers equals 100 grams, the total polyol mass. This ensures that the concentration of reactive groups is comparable to that in the actual foam. Water and catalysts are the same for both formulation and model. 

Hemibrevetoxin-B (15) is the smallest cyclic polyether compound produced by K. brevis [15]. Hemibrevetoxin-B has a polyether backbone and a terminal unsaturated aldehyde, similar to brevetoxin, but contains only four fused cyclic ether rings. Cytotoxicity of hemibrevetoxin-B against mouse neuroblastoma cells was reported. 

Analysis of the MD simulations of the PEPE5 reveal that Li" occurs primarily by hopping of the cation from one side chain to another [60]. The six oxygen atoms of the side chains facilitated coordination of Li", as anticipated. However, a fraction of Li" cations are partially coordinated by the polyether backbone. These cations have very slow dynamics and do not contribute appreciably to Li" motion. The slow dynamics of cations partially coordinated by the chain backbone can be understood by considering conformational dynamics in the comb-branch polymer. Figure 7.15 shows conformational relaxation time, based on... 

As mentioned previously, the reaction injection-molding process combines two precisely metered and well-mixed reactive streams. An example is the process that reacts catalyzed highly reactive streams of urethane components. One stream contains a polyether backbone, a catalyst, and a cross-linking agent. The other stream has an isocyanate. In addition, a blowing agent is included in one of the streams. 

Archibald, Manser, and coworkers developed a series of analogs of nitratoalkyl polymers (e.g., poly-NMMO and poly-BNMO). 3-(Difluor-aminomethyl)-3-methyloxetane (14) and 3,3-bis(difluoraminomethyl)oxetane (15) [100] monomers were prepared by direct fluorination of corresponding carbamate ester derivatives [101,102]. The monomers were polymerized (Scheme 11) to form homopolymers and copolymers with load-bearing polyether backbones as well as energetic NF2 groups. 

ID The relative amounts of the dipropylene glycols formed were nearly identical whether or not the polymer was treated with LAH. Thus, LAH treatment under the conditions used caused no isomerization of the polyether backbone. 

Inverse structures have been published for use in polyurethane foam formation [43]. Monofunctional siloxane chains are attached to a multifunctional polyether backbone. However, significant advantages over classical silicone surfactant structures could not demonstrated. A major drawback of this approach is the difficult synthesis of monofunctional siloxanes. 

Generally, the polyol will have either a polyester or a polyether backbone. The polyurethane elastomers based on an ester backbone generally have better abrasion resistance, tensile strength, tear strength, and oil resistance. On the other hand, polyurethane elastomers based on a polyether backbone generally possess better low-temperature properties, resiliency, and resistance to hydrolysis. 

Polyether backbones are used sometimes for better low-temperature properties and resistance to water attack. 

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