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The phenyl ether polymers are a class of aromatic polyethers containing aromatic cycles in their main chain : Polyphenyl ether ( PPE ) and Poly ( " p " - phenylene oxide ) ( PPO ) .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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