Ether phenylene

A potentially valuable characteristic of such poly(ether-phenylene-ketone-phenylene-carborane-phenylene) systems is that they display enormously enhanced char yields (up to 95% on pyrolysis in air) compared with the yields... 

AppHcation of an adhesion-promoting paint before metal spraying improves the coating. Color-coded paints, which indicate compatibiHty with specific plastics, can be appHed at 20 times the rate of grit blasting, typically at 0.025-mm dry film thickness. The main test and control method is cross-hatch adhesion. Among the most common plastics coated with such paints are polycarbonate, poly(phenylene ether), polystyrene, ABS, poly(vinyl chloride), polyethylene, polyester, and polyetherimide. 

One class of aromatic polyethers consists of polymers with only aromatic rings and ether linkages ia the backbone poly(phenylene oxide)s are examples and are the principal emphasis of this article. A second type contains a wide variety of other functional groups ia the backbone, ia addition to the aromatic units and ether linkages. Many of these polymers are covered ia other articles, based on the other fiinctionahty (see Polymers containing sulfur, POLYSULFONES). 

Halogen Displacement. Poly(phenylene oxide)s can also be prepared from 4-halo-2,6-disubstituted phenols by displacement of the halogen to form the ether linkage (48). A trace of an oxidizing agent or free radical initiates the displacement reaction. With 4-bromo-2,6-dimethylphenol, the reaction can be represented as in equation 10 ... 

Halophenols without 2,6-disubstitution do not polymerize under oxidative displacement conditions. Oxidative side reactions at the ortho position may consume the initiator or intermpt the propagation step of the chain process. To prepare poly(phenylene oxide)s from unsubstituted 4-halophenols, it is necessary to employ the more drastic conditions of the Ullmaim ether synthesis. A cuprous chloride—pyridine complex in 1,4-dimethoxybenzene at 200°C converts the sodium salt of 4-bromophenol to poly(phenylene oxide) (1) ... 

The effect of a second polymer blended with PPS which causes enhanced nucleation of PPS has been previously observed. It was found that low concentrations (1—2 wt %) of poly(phenylene sulfide ketone) and poly(ether ether ketone), when melt-blended with PPS, function effectively to increase the nucleation density of PPS (149). 

Alkylated phenol derivatives are used as raw materials for the production of resins, novolaks (alcohol-soluble resins of the phenol—formaldehyde type), herbicides, insecticides, antioxidants, and other chemicals. The synthesis of 2,6-xylenol [576-26-1] h.a.s become commercially important since PPO resin, poly(2,6-dimethyl phenylene oxide), an engineering thermoplastic, was developed (114,115). The demand for (9-cresol and 2,6-xylenol (2,6-dimethylphenol) increased further in the 1980s along with the growing use of epoxy cresol novolak (ECN) in the electronics industries and poly(phenylene ether) resin in the automobile industries. The ECN is derived from o-cresol, and poly(phenylene ether) resin is derived from 2,6-xylenol. 

Poly(phenylene ether). The only commercially available thermoplastic poly(phenylene oxide) PPO is the polyether poly(2,6-dimethylphenol-l,4-phenylene ether) [24938-67-8]. PPO is prepared by the oxidative coupling of 2,6-dimethylphenol with a copper amine catalyst (25). Usually PPO is blended with other polymers such as polystyrene (see PoLYETPiERS, Aromatic). However, thermoplastic composites containing randomly oriented glass fibers are available. 

Poly(phenylene ether) Alloys. Poly(phenylene ether) resins (91), composed of phenoHc monomers, have a very high T. The commercial resins are based on 2,6-dimethylphenol. The resin is produced by oxidative polymerization in toluene solution over an amine catalyst (see also PoLYETPiERS, aromatic). 

Table 10. Properties of Poly(phenylene ether)-based Resins ...

Worldwide sales of poly(phenylene ether)—styrene resin alloys are 100,000—160,000 t/yr (47,96) aimual growth rates are ca 9%. Other resin, particularly acrylonitrile—butadiene—styrene (ABS) polymers and blends of these resins with PC resins, compete for similar appHcations. 

Phenylene diisothiocyanate (bitoscanate) [4044-65-9] M 192.3, m 129-131", 130-131", 132". Purified by recrystn from AcOH, pet ether (b 40-60"), Me2CO or aq Me2CO. [van der Kerk et al. Reel Trav Chim Pays-Bas 74 1262 I955 Leiber and Slutkin J Org Chem 27 2214 7962.]... 

Various 2,6-di8ubstituted p-benzoquinones have been prepared by oxidation of the corresponding 2,6-disubstituted phenols with potassium nitrosodisulfonate or lead dioxide in formic acid. Oxidative coupling of 2,6-disubstituted phenols to poly-2,6-disubstituted phenylene ethers followed by treatment of the polymers in acetic acid with lead dioxide is reported to give low yields of the corresponding 2,6-disubstituted p-benzoquinones. 

The successful development of polyfethylene terephthalate) fibres such as Dacron and Terylene stimulated extensive research into other polymers containing p-phenylene groups in the main chain. This led to not only the now well-established polycarbonates (see Chapter 20) but also to a wide range of other materials. These include the aromatic polyamides (already considered in Chapter 18), the polyphenylene ethers, the polyphenylene sulphides, the polysulphones and a range of linear aromatic polyesters. 

In 1965 the poly-(2,6-dimethyl-/7-phenylene ether) was introduced as polyphenylene oxide (misleadingly ) and also as PPO by the General Electric Co. in the USA and by AKU in Holland. The commercial materials had a molecular weight of 25 000-60 000. 

The simplest aromatic polysulphone, poly-(p-phenylene sulphone) (formula I of Table 21.3) does not show thermoplastic behaviour, melting with decomposition above 500°C. Hence in order to obtain a material capable of being processed on conventional equipment the polymer chain is made more flexible by incorporating ether links into the backbone. 

Poly(ethylene terephtlhalate) Phenol-formaldehyde Polyimide Polyisobutylene Poly(methyl methacrylate), acrylic Poly-4-methylpentene-1 Polyoxymethylene polyformaldehyde, acetal Polypropylene Polyphenylene ether Polyphenylene oxide Poly(phenylene sulphide) Poly(phenylene sulphone) Polystyrene Polysulfone Polytetrafluoroethylene Polyurethane Poly(vinyl acetate) Poly(vinyl alcohol) Poly(vinyl butyral) Poly(vinyl chloride) Poly(vinylidene chloride) Poly(vinylidene fluoride) Poly(vinyl formal) Polyvinylcarbazole Styrene Acrylonitrile Styrene butadiene rubber Styrene-butadiene-styrene Urea-formaldehyde Unsaturated polyester... 

The presence of ether linkages in the polymer molecule imparts chain flexibility, lowers glass transition temperature, and enhances solubility while maintaining the desired high temperature characteristics [192]. Recently, polyether imines were prepared by the reaction of different diamines with 4,4 -[l,4-phenylene bis(oxy)] bisbenzaldehyde [184]. The polymers synthesized by the solution method were yellow to white in color and had inherent viscosities up to 0.59 dl/g in concentrated H2SO4. Some of these polyimines can be considered as... 

Dendrimers have structures similar to that of hyperbranched polymer and can be taken as the perfectly branched polymer with monodispersity. However, they need to be prepared by a multistep procedure. Therefore, very little work has been done on dendritic polyfarylcnc ether)s. Morikawa et al. prepared a series of monomers with a various number of phenylene units.164,165 These monomer were used to prepare poly(ether ketone) dendrons with graded structures (Scheme 6.24). 

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