Polyether glycols, formation

To produce a spandex fiber by reaction spinning, a 1000—3500 molecular weight polyester or polyether glycol reacts with a diisocyanate at a molar ratio of about 1 2. The viscosity of this isocyanate-terrninated prepolymer may be adjusted by adding small amounts of an inert solvent, and then extmded into a coagulating bath that contains a diamine so that filament and polymer formation occur simultaneously. Reactions are completed as the filaments are cured and solvent evaporated on a belt dryer. After appHcation of a finish, the fibers are wound on tubes or bobbins and rewound if necessary to reduce interfiber cohesion. 

Polyethers are also products of commercial importance. Ethers can be formed by thermal dehydration, as shown for the formation of dipropylene glycol from propylene glycol. CycHc ethers can form by elimination of water from di- or tripropylene glycol. 

The compound known as 18-crown-6 is one of the simplest and most useful of the macrocyclic polyethers. Its synthesis in low yield was first reported by Pedersen. Greene and Dale and Kristiansen" have reported syntheses of the title compound from triethylene glycol and triethylene glycol di-p-toluenesulfonate. Both of these procedures use strong base and anhydrous conditions and achieve purification by more or leas classical methods. The combination of distillation and formation of the acetonitrile complex affords crown of high purity without lengthy chromatography or sublimation. ... 

Dynamic transacetalization experiments targeting cyclophane formation have also been described by Mandolini and coworkers [34]. Production of a cyclic polyether DCL by direct reaction of triethylene glycol and 4-nitrobenzaldehyde has been reported by Berkovich-Berger and Lemcoff amplification of small macrocyclic members of the library by ammonium ion was observed [35]. With these few examples demonstrating feasibility, we can anticipate increased use of transacetalization in future DCC efforts. 

It is necessary to mention in particular the application of carboxylates of lanthanides instead of halides in the reactions with Li, Na, and K, alkoxides for the preparation of M(OR)3 -derivatives of almost all the lanthanides patented by Ozaki. The methoxides and n-buthoxides were thus obtained by interaction of formates with NaOR, the ethoxides by that of propionates with LiOEt, n-and isopropoxides by reaction of acetates or bensoates with LiOPr, t-buthox-ides by that of oxalates with KOBu [1246]. In addition to carboxylates for the interaction with NaOR using the easily accessible anhydrous Ln(OCOCCl3)3 [1494, 1159] was proposed. The adducts of Ln(N03)3 with glycols or polyethers were used for the preparation ofphenoxides [73]. 

Among the terephthalate-based polyether-ester copolymers, those prepared using 1,4-butanediol as the diol monomer exhibit the best overall physical properties. The use of ethylene glycol as the diol monomer retards the rate of polymer formation and results in copolymers which crystallize slowly. Other aliphatic ,w-diols yield terephthalate-based polyether-ester copolymers which are low in tensile strength and tear strength relative to the 1,4-butanediol-based copolymer. Terephthalate-based copolymers prepared with 1,4-benzenedimethanol as the diol monomer are relatively low in inherent viscosity, tensile strength, and tear strength. 

Some of the most familiar reactions falling into the polycondensation class are those leading to polyamides derived from dicarboxylic acids and diamines, polyesters from glycols and dicarboxylic acids, polyurethanes from polyols and polyisocyanates, and polyureas from diamines and diisocyanates. Similar polymer formations utilizing bifunctional acid chlorides with polyols or polyamines also fall into this class. The condensations of aldehydes or ketones with a variety of active hydrogen compounds such as phenols and diamines are in this group. Some of the less familar polycondensation reactions include the formation of polyethers from bifunctional halogen compounds and the sodium salts of bis-phenols, and the addition of bis-thiols to diolefins under certain conditions. 

Solutes held firmly in the vehicle exhibit low activity coefficients (low escaping tendencies) and thus low rates of penetration. Differences occur in the activity of phenols in mineral oil and polypropylene glycol bases. The latter are bland, the former corrosive. Polyether-phenol complex formation decreases the thermodynamic activity of the phenols, which are therefore less toxic. 

Peptide-poly(ethylene glycol) (PEG) block copolymers are ofparticiflar interest, both from a structural and a functional point of view. Poly(ethylene glycol) is also often referred to as poly(ethylene oxide) (PEG). Throughout this article, however, this polyether will be referred to as PEG. In contrast to the hybrid block copolymers discussed in the previous paragraphs, which were based on amorphous synthetic polymers, PEG is a semi-crystalline polymer. In addition to microphase separation and the tendency of the peptide blocks towards aggregation, crystallization of PEG introduces an additional factor that can influence the structure formation of these hybrid block copolymers, furthermore, PEG is an FDA approved biocompatible polymer, which makes peptide-PEG hybrid block copolymers potentially interesting materials for biomedical applications. 

Two methods to prepare polyether-based podands are described here. The first is a direct modification of polyethylene glycols and comes originally from the work of Piepers and Kellogg [6], later modified by Hosseini [7]. A simple reaction between hexaethylene glycol and isonicotinyl chloride, as shown in Figure 1.2, results in the formation of podand 1 in good yield. When treated with silver salts... 

The principle of formation of segmented or block copolymers (see Section 4.4.5) has also been applied to polyesters, with the hard segment formed from butanediol and terephthalic acid, and the soft segment provided by a hydroxyl-terminated polyether [polytetramethylene either glycol (PTMEG)] with molecular weight 600-3000. 

I.2. Propylene Chlorohydrin. Propylene chlorohydrin is one of the most important intermediates used in the production of PO, which is a raw material for producing propylene glycols and urethane polyether polyols. The United States and Western Europe are the largest producers of propylene chlorohydrin, accounting for 74% of the world s production. The main environmental issues relate to the chlorinated waste generated in the process and the disposal of the byproduct calcium chloride sludge. The formation of... 

An alternative method of obtaining water solubility, without salt or ion formation, is to incorporate short lengths of naturally water-soluble polymer into the main polymer structure. Often polyethene glycol is used. This is a polyether (Chapter 15) of molecular weight about 1000, which is made from ethylene oxide and ethylene glycol. Between 5 and 20% by... 

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