Polyol Synthesis

A variety of solution methods such as seed-assisted growth, template-based synthesis, polyol method, solvothermal method and oriented attachment have also been developed for the synthesis of one-dimensional nanostructures. Here we will present various examples of the nanowires including metals, oxides, chalcogenides and pnictides with different synthetic methods. 

Method of synthesis - polyol(s) are dried by azeotropic distllatlon (e.g., with toluene), catalyst Is added followed by addition of Isocyanate Ojha, U Kulkarni, P Faust, R, Polymer, 50, 3448-57, 2009. 

Polyhydric Alcohols. The principal types of polyol used in alkyd synthesis are shown in Table 3. 

Poly(Oxyethylene-coOxypropylene) Nonionic Surfactants. A great variety of these surfactants is marketed by BASE Corporation under the Pluronic polyol trademark. The synthesis foUows ... 

Synthesis MDI prepolymer with 1000 MW polyester polyol, NCO/OH = 2.0, chain-extended with 1,4-butandiol, acid number of polyester 0.6. 

The synthesis of the polyol glycoside subunit 7 commences with an asymmetric aldol condensation between the boron enolate derived from imide 21 and a-(benzyloxy)acetaldehyde (24) to give syn adduct 39 in 87 % yield and in greater than 99 % diastereomeric purity (see Scheme 8a). Treatment of the Weinreb amide,20 derived in one step through transamination of 39, with 2-lithiopropene furnishes enone 23 in an overall yield of 92 %. To accomplish the formation of the syn 1,3-diol, enone 23 is reduced in a chemo- and... 

The completion of the synthesis of the polyol glycoside subunit 7 requires construction of the fully substituted stereocenter at C-10 and a stereocontrolled dihydroxylation of the C3-C4 geminally-disub-stituted olefin (see Scheme 10). The action of methyllithium on Af-methoxy-Af-methylamide 50) furnishes a methyl ketone which is subsequently converted into intermediate 10 through oxidative removal of the /j-methoxybenzyl protecting group with DDQ. Intermediate 10 is produced in an overall yield of 83 % from 50) , and is a suitable substrate for an a-chelation-controlled carbonyl addition reaction.18 When intermediate 10 is exposed to three equivalents of... 

When hydrogenolysis of vinylepoxides is used sequentially, it allows for the controlled formation of 1,3-polyols. In the synthesis of the C11-C23 fragment 92 of preswinholide A, hydrogenolysis of ( ) olefin 93 gave the syn isomer 94 (Scheme 9.37) [159]. Methylation, reduction, epoxidation, oxidation, and olefmation of this material then gave vinylepoxide 95, which was subjected to hydrogenolysis to afford 96 in excellent yield. Repetition of this sequence ultimately afforded the desired derivative 94. 

Hie most representative member of this class of polyesters is the low-molar-mass (M 1000-3000) hydroxy-terminated aliphatic poly(2,2/-oxydiethylene adipate) obtained by esterification between adipic acid and diethylene glycol. This oligomer is used as a macromonomer in the synthesis of polyurethane elastomers and flexible foams by reaction with diisocyanates (see Chapter 5). Hydroxy-terminated poly(f -caprolactonc) and copolyesters of various diols or polyols and diacids, such as o-phthalic acid or hydroxy acids, broaden the range of properties and applications of polyester polyols. 

Alkyd resin synthesis. This synthesis consists of two steps. In the first step, a triglyceride oil is reacted at ca. 250°C with polyols, such as glycerol or pentaery-thritol, in tire presence of a basic catalyst to form a monoglyceride. In the second step, phthalic anhydride, with or without another dibasic acid such as maleic anhydride, is added to the reaction medium and reacted at high temperature. The resulting product is a branched polyester (Scheme 2.56). 

Polyols and polyamines are the most important coreactants for isocyanates. As briefly outlined in Section 4.2.2, the two most common classes of urethane-grade polyols are the polyethers and polyesters. In this section their synthesis and structure are discussed. Other polyol types, such as acrylic resins and polycarbonates, are of more limited applicability and are not presented here. 

Poly(tetramethylene oxide) polyols (see Scheme 4.4) are a special class of polyethers syndiesized via acid-catalyzed ring-opening polymerization of tetrahy-drofuran. Although less susceptible to side reactions, the synthesis of these C4 ethers is less flexible in terms of product composition and structure. Thus, because of diis syndietic route, only two-functional glycols are available and copolymers are not readily available. Molecular weights of commercial C4 glycols range up to about 3000 g/m. 

Scheme 4.12 Conventional synthesis of polyether polyols via base-catalyzed ring-opening polymerization of alkylene oxides.

Ethane linkages, 407 Ethene linkages, 407 Ethylene adipates, 212 Ethylene-CO copolymer, 460 Ethylene copolymers, 446 Ethylene glycol (EG), 13, 64. See also EG polyester synthesis depolymerization with, 559 repolymerization of, 561-562 Ethylene oxide (EO) polyols, 211... 

Polyether-PA segmented copolymers, synthesizing, 191-192 Polyether polyols, 200, 205, 211-212 synthesis of, 223, 224 Poly(ether sulfone) (PES), 327. See also Poly(arylene ether sulfone)s Poly(phenylene ether sulfone) chains Sulfonated poly (ary lene ether sulfone)... 

Poly(phenylenethylene), dendronized, 522 Poly(phenylenevinylene) optically active, 510-511 synthesis of, 495-496 Poly(/ ara-phenylenevinylene)s, 472 Polypheny lquinoxaline (PPQ) hyperbranched, 312-314 synthesis of, 309-313 Polyphosphoric acid, 333 Polypropylene oxide) polyol, 223 Polypropylene polyols, 220 Poly (pyridine), synthesis of, 503-505 Polyquinoxaline (PQ), synthesis of, 309-313... 

---