Aromatic Linked by Aliphatic or Functional Group

This class of polymers is quite stable at high temperatures, but not as stable as the polyimides or other materials described in the preceding 

Thermal stability decreases as substitution on the aromatic nuclei increases. 

In the case of polyphenylene oxides, the thermal stability of various substitutions are, in decreasing order, QH5 CH3 CH2-CH-CH2 C6H5SO3 OH SO3H SO2CI. 

For polyphenylene sulfides the presence of an ether linkage enhances the thermal stability in some cases, but in others it decreases the thermal stability. If there is no ether or isopropylidene linkages, the order of stability is biphenyl phenyl. 

Polyphenylene oxide (Noryl from GE) and polyphenylene sulfide (Ryton from Phillips) are used as high-temperature engineering plastics. Polyphenyl ether sulfones are manufactured by a number of companies under a variety of trade names including 720P, 220P by ICI and RADEL by Union Carbide. They are generally used as injection-moldable thermoplastics and in the adhesive and composite industry. 

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