Polyphenyl Ether - Structure and Synthesis of PPEs

Structure and Synthesis of PPEs

The proper name for a phenyl ether polymer is poly(phenyl ether) or polyphenyl polyether, but the name polyphenyl ether is widely accepted. Polyphenyl ethers (PPEs) are obtained by repeated application of the Ullmann Ether Synthesis: reaction of an alkali-metal phenate with a halogenated benzene catalyzed by copper.

PPEs of up to 6 phenyl rings, both oxy and thio ethers, are commercially available. See Table 1. They are characterized by indicating the substitution pattern of each ring, followed by the number of phenyl rings and the number of ether linkages. Thus, the structure in Figure 1 with n equal to 1 is identified as pmp5P4E, indicating para, meta, para substitution of the three middle rings, a total of 5 rings, and 4 ether linkages. Meta substitution of the aryl rings in these materials is most common and often desired. Longer chain analogues with up to 10 benzene rings are also known.

The simplest member of the phenyl ether family is diphenyl ether (DPE), also called diphenyl oxide, the structure of which is provided in Figure 4. Low molecular weight polyphenyl ethers and thioethers are used in a variety of applications and include high vacuum devices, optics, electronics, and in high-temperature and radiation-resistant fluids and greases. Figure 5 show the structure of the sulfur analogue of 3-R polyphenyl ether shown in Figure 3.