Depolymerization of poly(2,6-dimethyl-1,4-phenylene oxide) under oxidative conditions

Kei Saito, Toru Masuyama, Kenichi Oyaizu, Hiroyuki Nishide

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Depolymerization of an engineering plastic, poly(2,6-dimethyl-1, 4-phenylene oxide) (PPO), was accomplished by using 2,6-dimethylphenol (DMP) under oxidative conditions. The addition of an excess amount of DMP to a solution of PPO in the presence of a CuCl/pyridine catalyst yielded oligomeric products. When PPO (Mn = 1.0 × 104, M w/Mn = 1.2) was allowed to react with a sufficient amount of DMP, the molecular weight of the product decreased to Mn = 4.9 × 102 (Mw/Mn = 1.5). By a prolonged reaction with the oxidant, the oligomeric product was repolymerized to produce PPO essentially identical to the starting material, making the oligomer useful as a reusable resource. During the depolymerization reaction, an intermediate phenoxyl radical was observed by ESR spectroscopy. Kinetic analysis showed that the rate of the oxidation of PPO was about 10 times higher than that of DMP. These results show that a monomeric phenoxyl radical attacks the polymeric phenoxyl to induce the redistribution via a quinone ketal intermediate, leading to the substantial decrease in the molecular weight of PPO, which is much faster than the chain growth.

Original languageEnglish
Pages (from-to)4240-4246
Number of pages7
JournalChemistry - A European Journal
Volume9
Issue number17
DOIs
Publication statusPublished - 2003 Sep 5

Keywords

  • Depolymerization
  • Green chemistry
  • Polymerization
  • Polyphenyleneoxide
  • Reaction mechanisms

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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