Chemical and physical properties of low-molecular-weight poly(2,6-dimethyl-1,4-phenylene oxide) (LMW-PPO) synthesized by peroxydisulfate and metal/non-metal catalysts

• Published in: Polymer chemistry 2023-04, Vol.14 (16), p.1933-1944
• Main Authors: Lu, Yi-Fang, Wu, Song-Hai, Wang, Cong, Liu, Yong, Huang, Fu-Gen, Song, Bao-Dong, Han, Xu
• Format: Article
• Language: English
• Subjects: Catalysts; Copper; Dielectric properties; Insulation; Manganese; Oxidation; Oxidizing agents; Physical properties; Polydimethyl phenylene oxide; Polymer chemistry; Thermal stability
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/d2py01614a

Preparing low-molecular-weight poly(2,6-dimethyl-1,4-phenylene oxide) (LMW-PPO) with high thermal stability and satisfactory dielectric properties is a challenge. Herein, we reported two methods for synthesizing LMW-PPO using metal and non-metal catalysts. In the presence of Cu( ii ), PPO with an M n of 6.0 × 10 3 can be obtained with peroxydisulfate (PDS) as the oxidant. In the absence of Cu( ii ) catalysts, mesoporphyrin IX dihydrochloride or methylamine can also catalyze PDS to produce low-molecular-weight and metal-free PPO ( M n of 4.9 × 10 3 or 4.6 × 10 3 ). PDS not only mediates the oxidation of Cu( i ) to Cu( ii ) with Cu( ii ) catalysts, which is an important step for binding phenolates to form LMW-PPO, but also abstracts H from DMP to give DMP radicals, which then polymerize to LMW-PPO in the absence of the Cu( ii ) catalysts. In addition, PDS can effectively break the long-chain PPO to give shorter PPO, thus effectively mediating the molecular weight of PPO. Additionally, the decrease in T g values from 215 °C to 159 °C with decreasing M n of PPO mediated by peroxydisulfate indicate its improved processability while maintaining high thermal stability ( T d5% = 427 °C-439 °C). The satisfactory dielectric properties of the PPO obtained using PDS and metal-free catalysts also imply its high potential to be used for insulating materials. Low-molecular-weight poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) can be obtained by peroxydisulfate and Cu(ii)/metal-free catalyst, and high-molecular-weight PPO can be mediated to shorter ones by peroxydisulfate.