Depolymerization of Poly(2,6‐dimethyl‐1,4‐phenylene oxide) under Oxidative Conditions

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 (M(n)=1.0x10(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)=4.9x10(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.

Synthesis and physical properties of low‐molecular‐weight redistributed poly(2,6‐dimethyl‐1,4‐phenylene oxide) for epoxy resin

“…Low‐molecular‐weight PPO was prepared when bisphenols were brought into a reaction with regular PPO in the presence of a suitable initiator 21, 22, 25–27. On the basis of the free‐radical redistribution reaction, BPO was one of the effective initiators reported by White and others 23, 29.…”

“…Redistribution (depolymerization) is an elegant method for obtaining low‐molecular‐weight PPO with a phenolic tail‐end group 20. Most of the previous redistribution studies of PPO have emphasized the understanding of the redistribution mechanism and the screening of potential initiators and phenols 21–27. Few researchers have studied the effects of low‐molecular‐weight redistributed poly(2,6‐dimethyl‐1,4‐phenylene oxide) (rPPO) with a terminal phenolic group on the physical properties of the epoxy network.…”

Low dielectric and flame‐retardant properties of thermosetting redistributed poly(phenylene oxide)

“…Low-molecular-weight PPO was obtained from the free-radical redistribution reaction of MA with regular PPO in the presence of BPO as an initiator [10,11]. The decrease in molecular weight dur-ing the redistribution reaction was followed by GPC, as shown in Fig.…”

Synthesis and Properties of Poly(phenylene ether) Diblock Copolymers Bearing Acid Substituents

“…The results suggested that the acid substituents attached onto the pendant phenyl groups were more stable than those on main chains. KEY WORDS Oxidative Polymerization / Poly(phenylene ether) / Block Copolymer / Polymer Electrolyte / Fuel Cell/ (Received May 7, 2007: Accepted September 4,2007) [ Kobunshi Ronbunshu, 65, 145-149 (2008)]…”