Synthesis And Characterization Of Modified Polyphenylene Oxide For High Speed And High Frequency CCLs

Polyphenylene oxide(PPO)has excellent comprehensive properties such as low dielectric property,heat resistance and dimensional stability.It can use the traditional molding process and equipment of copper clad laminates made by epoxy,which shows great application potential in the field of high speed and high frequency electronic devices.However,due to the high molecular weight and few reactive groups of commercial PPO,it is difficult to realize self-crosslinking or composite with other resins.As a result,the performance advantages of PPO cannot be fully utilized in the field of CCL.The main goal of this thesis is to synthesize the modified PPO with low molecular weight and multi-functionalization for high frequency and high speed CCLs.Based on redistribution reaction and end-group modification reaction technology,a variety of low molecular weight modified PPO,such as double-terminated hydroxyl PPO,threeterminated hydroxyl PPO and PPO with terminated methacrylate group,were synthesized by molecular structure design and reaction conditions optimization.Their curing behavior and properties were investigated.The thesis achieved the following results:1.Based on the proportional relationship between the differential UV absorbance and the concentration of phenol hydroxyl before and after ionization,a differential UV spectrometric method for quantitative determination of phenol hydroxyl in PPO was established.It was found that there was some high molecular weight PPO in the product which could not be depolymerized by the redistribution reaction of PPO with phenols.And then a method of grading the redistribution reaction product by using toluene/methanol as good/poor solvents was proposed.When 18 wt%methanol was used,PPO with high Mn could be completely removed,and the modified PPO with low Mn was obtained.2.A variety of low molecular weight PPO with double terminal phenolic hydroxyl groups were synthesized by the redistribution reaction of tetramethylbisphenol A(TMBPA),bisphenol A(BPA)and hexafluorobisphenol A(BPAF)with PPO,respectively.The ortho position of the phenolic hydroxyl group of TMBPA contains an electron-contributing methyl group,which shows a high redistribution activity and the Mn of PPO could be reduced to 2000,while the electron-withdrawing trifluoromethyl group can reduce the redistribution reactivity of BPAF,indicating that the structure of phenolic substance has a great influence on the redistribution reactivity.These three kinds of hydroxyl modified PPO can be cured with epoxy resin to reduce the dielectric constant(Dk)and dielectric loss(Df)of cured resin,especially the Dk of BPAF-PPO and epoxy resin curing system with fluorine-element is lower.3.1,1,1-Tris(4-hydroxy phenyl)ethane(THPE)was redistributed with PPO,and a low Mn PPO(THPE-PPO)with three terminal hydroxyl function was successfully synthesized.THPE and PPO showed high reactivity,the molecular weight of the product collected by total separation method was as low as 1724.The solubility and reactivity of THPE-PPO in epoxy resin were significantly higher than that of double hydroxyl terminated PPO,which could improve the heat resistance of composite curing with epoxy resin and maintain excellent dielectric properties.In addition,THPE-PPO can be directly crosslinked with decafluorobiphenyl(DFBP)in N-methylpyrrolidone,and the dielectric constant of cross-linking products is as low as 2.31 and the glass transition temperature is 222.6?.4.Three terminal allyl functionalized modified PPO with low molecular weight(THPE-PPO-3V)was prepared,by esterification of methacrylic anhydride(MAAH)with phenolic hydroxyl groups of THPE-PPO.There is no need for THPE-PPO-3V to be compounded with epoxy resin,and it can be directly triggered by peroxide to achieve self-crosslinking product.It has better dielectric properties and temperature resistance,compared with THPE-PPO/epoxy resin composite curing material.