Polyethers, preparation

Polyethers prepared from propylene oxide are soluble in most organic solvents. The products with the highest hydroxyl number (lowest molecular weight) are soluble in water, not in nonpolar solvents such as hexane. The solubihty of 3000 molecular weight triols is high enough in solvents such as toluene, hexane, and methylene chloride that the triols can be purified by a solvent extraction process. 

The advantage of the activated displacement polymerization is the facile incorporation of different and unconventional structural units in the polymer backbone. Most of the heteroarylene activated polyethers prepared by this route are soluble in many organic solvents. The solubility behavior of new polyethers is shown in Table 8. In contrast to many polyphenylenequi-noxalines, poly(aryl ether phenylquinoxalines) prepared by the quionoxaline activated displacement reaction are soluble in NMP. Solubility in NMP is important since it is frequently used for polymer processing in the microelectronics industry [27]. 

C—S—C) in the main chain. The new polyethers prepared either by new heteroarylene activated or by aromatic activated systems have good melt processability. The thermal stability and glass transition temperature of bisphenol-A based new polymers are shown in Table 10. 

Polyethers prepared by reaction with diepoxides have been described.79 Such reactions have been achieved from sucrose or partially esterified sucrose for the preparation of polymeric resins used as coating agents.78 Polysucrose (Ficoll400 ), a water-soluble copolymer prepared from sucrose and epichlor-hydrin, has been developed on the industrial scale. It is used as a biocompatible additive for cell separation and diagnostics, and is also described as having valuable properties as a food ingredient.18 Sucrose dicarboxylates can react with diamines to provide polyamides.183... 

In addition to step and chain polymerizations, another mode of polymerization is of importance. This is the ring-opening polymerization of cyclic monomers such as cyclic ethers, esters (lactones), amides (lactams), and siloxanes. Examples of commercially important types are given in Table 10.1. Of those listed, only the polyalkenes are composed solely of carbon chains. Those that have enjoyed the longest history of commercial exploitation are polyethers prepared from three-membered ring cyclic ethers (epoxides), polyamides from cyclic amides (lactams), and polysiloxanes from cyclic siloxanes. 

Epoxy resins are polyethers prepared from glycols and dihalides and are extensively used as surface coatings, adhesives, and flexible enamel-like finishes because of their combined properties of toughness, chemical resistance, and flexibility. 

For the copol)nners, PHMS-5,7-20 specifies the copolymer synthesized from HMS, 20 mole% 1,5-dibromopentane and 80 mole% 1,7-dibromoheptane. Likewise, the polyether prepared from HB, 30 mole% 1,7-dibromoheptane and 70 mole% 1.9 dibromononane will be termed PHB-7,9-30. 

Another class of polymers are the polyethers, prepared by ring-opening reactions. The most important member of this series is poly(ethylene oxide). 

Almost all LC-polyethers mentioned in this section were prepared via the Williamson ether synthesis from a mesogenic diphenol and (di)bromoalkanes. For instance a linear LC-polyether was obtained from the cesium salt of a diazine-diphenol and 1,10-dibromodecane in NMP (210) [323]. In two cases, (211) [324] and (209) [325] interfacial polycondensation were performed using sodium hydroxide in combination with a phase-transfer catalyst and an organic solvent. Almost all LC-polyethers prepared in this... 

The presence of phenoxy endgroups in polyethers prepared by thermal initiation of epoxides with diaryliodonium salts was verified by ultraviolet spectroscopy (15), but the authors do not comment on the fraction of such endgroups (i.e., on the relative importance of Eqns. 2c and 2e). 

From these results, the following structure can be proposed for the polyethers prepared by PTC polycondensation ... 

Fig. 3 Dependence of of polyethers prepared under PTC conditions on the ratio [BPA]/[DCB] (toluene/NaOH 3N 10 ml/lO ml, TBAH 10 % mol, 65 C, magnetic stirring).

Table 7. Properties of Polyethers Prepared by PTP of Bisphenols and 1,6-Dibromohexane...

Properties of hyperbranched polyethers prepared by cationic polymerization of glycidol have also been studied. Cationically prepared polyglycidol after esterification of hydroxyl end-groups with palmitoyl chloride showed an interesting self-assembly behavior. Depending on the solvent and content... 

The synthesis of the poly(alkylene oxide)s for elastomers is contained in Chapter 4, Sections III. A, IV, and V. For polyurethane elastomers based on propylene oxide, the polyethers prepared are secondary hydroxyl-terminated polyethers. The secondary hydroxyl group is slower to react with isocyanate than is a primary hydroxyl (Table 3) (20). Therefore, poly(propylene oxide) diols and higher functionality polyols are often capped with ethylene oxide (see Chapter 4, Sections IV and V) to obtain the more reactive terminal, primary hydroxyl groups. 

Fig. 12.1 MALDI-TOF mass spectrum of a multicyclic polyether prepared from THPE and 2,6-difluoropyridine with a feed ratio of 1.0/1.52. Figure 4 reproduced from Ref. [13] with permission (Copyright 2004, Wiley Periodicals)...

---