High molecular weight polymers polyethers

Polyether polyols are high molecular weight polymers that range from viscous liquids to waxy solids, depending on structure and molecular weight. Most commercial polyether polyols are based on the less expensive ethylene or propylene oxide oi on a combination of the two. Block copolymers are manufactured first by the reaction of propylene glycol with propylene oxide to form a homopolymer. 

High purity 4,4 -diphenoxy benzophenone is a key starting material for the production of high molecular weight polymers. Thus, its polycondensation with terephtaloyl chloride in presence of Friedel-Crafts catalyst gives polyether-ether ketones (PEEK) with the structure depicted on scheme 17 ... 

Hydroxyl-Terminated Urethane Polyethers. Hydroxyl-terminated urethane polyethers are polyether polyols extended with diisocya-nates to medium high molecular weight polymers employing a low NCOtOH ratio. 

These hydroxy-terminated polyesters may have applications as prepolymers for other high molecular weight polymers. These could condense with diisocyanates to produce polyurethane foams [44], either flexible or rigid. They also may have compatibility with epoxy resins and polyester to give rise to polyester epoxy resins, polyester-polyamide [41], and polyester-polyether copolymers. The further condensation with some unsaturated monomer may result in thermoset film formers. They can be used as a mildness additive in metal-working lubricants. 

The chemical structure and molecular weight of the polymer both influence the rate of coagulation and the structure produced. A high molecular weight polymer coagulates more rapidly than one of lower molecular weight. It is found that in a DMF/water system, a polyether-based polymer coagulates more rapidly than a polyester-based polymer of the same urethane content. 

Nucleophilic displacement chemistry involving aromatic dihalides and bisphenois, represented the first means by which high molecular weight aromatic polyethers could be produced. This technology has since been the basis for all commercial processes developed for this family of Engineering Polymers. The preparative method involves the nucleophilic polycondensation of a bispheno salt with an activated aromatic dihalide in an aprotic solvent. Further investigations have shown that the method has a very wide scope and that it can be applied to the preparation of a host of aromatic poly (sulfone ethers), poly (ketone ethers) and other related polyethers. 

Poly(ethylene oxide)s [25372-68-3] are made by condensation of ethylene oxide with a basic catalyst. In order to achieve a very high molecular weight, water and other compounds that can act as chain terminators must be rigorously excluded. Polymers up to a molecular weight of 8 million are available commercially in the form of dry powders (27). These must be dissolved carefliUy using similar techniques to those used for dry polyacrylamides. Poly(ethylene oxide)s precipitate from water solutions just below the boiling point (see Polyethers, ethylene oxide polymers). 

The diisocyanates and polyols are reacted to form a high molecular weight hydroxyl terminated millable gum. These millable gums are compounded and processed as conventional elastomers, both sulphur and peroxides being used to cure the polymers. Here again, polyether and polyester types are available, and the differences between these two types referred to above also apply here. 

---