Ya-Qi Wang,Qing He,Zhi-Yang Zhang,Lei Zhang,Na-Juan Yuan,Yong Liu,Hai-Tao Ren,Xu Han
Although the low molecular weight poly(2,6-dimethyl-1,4-phenyl oxide) (LMW-PPO) has been extensively applied in the field of 5G communication, the complicated procedures involved in the synthesis of LMW-PPO and efficient recovery of the homogeneous catalysts are still challenging nowadays. In this study, five ionic liquids (ILs) have been successfully synthesized, and LWM-PPO is directly synthesized using different Cu(OAc) 2 -ILs complexes as catalysts. Among them, Cu(OAc) 2 - IL(a) not only exhibits the high yield of LWM-PPO (83.68%, M n =3.6✕10 3 ) with the low 3,3’,5,5’-tetramethyl-4,4’-diphenoquinone (DPQ) yield (0.12%) and polydispersity index (PDI, 1.39) in methanol, but also maintains high stability after being recycled for 5 times. In addition, with increasing H 2 O contents in the system from 1.0% to 5.0%, the M n values of PPO decrease from 2.9✕10 3 to 2.4✕10 3 with the narrow PDI values in the range of 1.22-1.45, indicating that trace H 2 O effectively promotes the formation of binuclear Cu(II) complex between Cu(OAc) 2 ·H 2 O and ILs, which then polymerizes 2,6-dimethylphenol (DMP) to LMW-PPO. The synthesized LMW-PPO exhibits high thermostability ( T d5% =427.07-430.52°C), low glass transition temperature ( T g =167.6-180.3°C), and low dielectric constant ( D k =2.14-2.64, 1 GHz) and dielectric loss ( D f =2.83✕10 -3 -4.91✕10 -3 , 1 GHZ), indicating that it is more appropriate to be used in the field of 5G communication. This study provides new insight on the importance of ILs in direct synthesis of LMW-PPO with high performances.
Traditional free radical polymerization has poor controllability, and traditional petroleum-based lubricant additives have adverse effects on the environment. Poly (lauryl methacrylate (LMA)-soybean oil (SBO)) (P(LMA-SBO) was synthesized using Salen-Cu(II) complex as a catalyst and azodiisobutyronitrile (AIBN) as an initiator by the Schlenk techniques. The structure of P(LMA-SBO) was characterized by infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC) followed by evaluating the solidification point depression performance by the Chinese standard method GB/T 510-2018, and the wax crystal morphology was studied by optical microscopy. The results show the catalytic activity could be 22.88 × 104 g·mol−1·h−1 and the number average molecular weight (Mn) of the copolymer is 8.71 × 104 with a low dispersity (Ɖ) of 1.37 under the optimal conditions, which indicates good controllability of the polymerization. Adding 1.0%(w) P(LMA-SBO) to the lubricating oil fraction (350–500 °C) could reduce the solidification point by 15 °C. Therefore, the Salen-Cu (II) catalyst was successfully applied to the controlled polymerization of LMA and SBO. The vegetable oil-based solidification point depressant of P(LMA-SBO) could be used as a potential alternative to replace the traditional solidification point depressant in the future.
Controlled radical polymerization (CRP) under external field has been an attractive research area in these years. In this work, a new electron transfer mechanism, that is, sonochemically induced electron transfer (SET) was introduced to mediate polymerization for the first time. The activator Cu I X/L complex was (re)generated from Cu II X 2 /L in dimethylsulfoxide (DMSO) by the SET process in the presence of free ligand tris(2-dimethylaminoethyl)amine (Me 6 TREN). The investigation of polymerization including the mechanistic insights and effect of experimental conditions on the rate of reaction has been undertaken. Kinetics of Cu(II)-catalyzed CRPs via SET under different conditions (i.e., Me 6 TREN concentration, catalyst loading, targeted degree of polymerization, and sonication power) were conducted in an unprecedentedly controlled manner, yielding polymers with predetermined molar masses and low dispersities ( Đ < 1.12). Attractively, the polymerization can be performed without the piezoelectric nanoparticles and exogenous reducing agent. Contamination by nonliving chains formed from sonochemically generated radicals is avoided as well. All of these results supported that Cu(II)-based catalyst activation enabled by ultrasonication has a promising potential in scale-up of CRP.
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