Study On Preparation And Properties Of Low-Molecular-Weight Polyphenylene Oxide For High Frequency And High Speed Copper Clad Laminate

Polyphenylene oxide resin is considered to be one of the most potential electronic packaging materials because of its excellent properties,such as excellent mechanical and dielectric properties,low water absorption and good thermal stability.The traditional polyphenylene oxide has the disadvantages of poor fluidity after melting,which leads to processing difficulties and hinders its application in electronic fields such as electronic packaging materials.Low molecular weight polyphenylene oxide can not only solve the above problems,but also has the excellent properties of high molecular weight polyphenylene oxide.Therefore,low molecular weight polyphenylene oxide have attracted attention in recent years.In this paper,the existing synthesis process of polyphenylene oxide is optimized,so that the molecular weight of the product can be controlled,and theα,ω-bis（2,6-dimethylphenol）-poly（2,6-dimethyl-1,4-phenylene oxide）（PPO-2OH）oligomer is crosslinked with cyanate resin.The work of this paper is divided into the following three parts:1)Low molecular weight polyphenylene oxide was prepared by solution polymerization.The product was identified as polyphenylene oxide（PPO-OH）by NMR and FT-IR.By exploring the effects of different reaction conditions on the product,the molecular weight of the product can be stably controlled in the range of 1500～4000,and the residual amount of copper catalyst in the product is very small.The relationship between glass transition temperature and molecular weight can be fitted by Fox-Loshaek equation and Fox-Flory equation.The thermal properties of the product are good,the initial decomposition temperature is about 420℃,and 20～30%char yield in N₂ atmosphere at 800℃.In addition to 2,6-dimethylphenol,4-bromo-2,6-dimethylphenol and 2,6-diphenylphenol can also be self-polymerized to obtain corresponding polymers.2)PPO-2OH oligomer was prepared by copolymerization of 2,6-dimethylphenol and 2,2-bis（4-hydroxy-3,5-dimethylphenyl）propane.The product was identified as PPO-2OH by NMR and FT-IR.By exploring the effects of different reaction conditions on the product,it is found that only the ratio of 2,6-dimethylphenol and 2,2-bis（4-hydroxy-3,5-dimethylphenyl）propane has a great influence on the molecular weight of the product,so the molecular weight of the product is basically controllable,and the residual amount of copper catalyst in the product is very small.Fox-Loshaek equation and Fox-Flory equation were used to describe the relationship between molecular weight and glass transition temperature.The temperature of the maximum thermogravimetric rate of the product is about 450～500℃,and 20～30%char yield in N₂ atmosphere at 800℃.The effect of bisphenol species on the product was studied.It was found that the presence of electron-donating substituent groups at 2,6-position was helpful to the formation of PPO-2OH oligomer.Some functionalized PPO-2OH derivatives were further synthesized by using the PPO-2OH and characterized by NMR.3)The composite of PPO-2OH/cyanate ester resin was synthesized by using PPO-2OH as modifier.Infrared spectroscopy showed that the molecular structure changed during the curing process,indicating that the curing cross-linking occurred.The introduction of PPO-2OH in the composite slightly reduces the original thermal stability and water absorption of cyanate ester resin,but improves the mechanical and dielectric properties of the material.The curing kinetics was studied by non-isothermal DSC method.The activation energy was calculated by Starink,KAS and other methods,and the kinetic equation of the curing process was obtained,and the fitting results of the equation were close to the experimental results.