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Depolymerization of Poly(2,6‐dimethyl‐1,4‐phenylene oxide) under Oxidative Conditions
Author(s) -
Saito Kei,
Masuyama Toru,
Oyaizu Kenichi,
Nishide Hiroyuki
Publication year - 2003
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200204669
Subject(s) - depolymerization , chemistry , phenylene , oligomer , monomer , polymer chemistry , polymerization , catalysis , pyridine , dimethyl terephthalate , condensation polymer , photochemistry , organic chemistry , polymer
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 ( M n =1.0×10 4 , M w / M n =1.2) was allowed to react with a sufficient amount of DMP, the molecular weight of the product decreased to M n =4.9×10 2 ( M w / M n =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.