Preparation And Properties Of New Thermosetting Fluorinated Poly(aryl Ether)

Poly(aryl ether)(PAE), including aryl unit and ether linkage has excellent radiation resistance, high heat resistance, low dielectric constant and good mechanical properties. As an important class of high-performance materials, the PAE has been widely used in the production of automobiles, computers, and telecommunications components, and used in the manufacturing of fibers used in the electrical and electronics industry reinforced composite materials as the matrix resin.Among various PAE, those containing fluoro groups have received much attention in the recent years.The introduction of fluorine atoms into PAE can endow the polymers with low dielectric constant and moisture uptake due to the low polarizability of the C-F bond and the surface energy of fluorine. Accordingly, many fluorinated PAE have been investigated and developed, of which the PAE containing perfluorophenyl units,-CF3 groups, and perfluorocyclobutane moieties are particularly gathering attention. These fluorinated PAE exhibit high glass transition temperature(Tg) and excellent optical properties, is expected to be used in areas such as optical communications, VLSI, and flat-panel displays.It is noted that benzocyclobutene(BCB) is a highly reactive molecule, when heated at high temperature, the four-membered ring on benzocyclobutene opens to produce a highly reactive o-quinodimethane intermediate. This active intermediate either forms a product with an eight-membered ring via self-coupling or produces a copolymer through the Diels-Alder reaction. Accordingly, our strategy is to incorporate BCB units into a fluorinated PAE as a side chain to improve the dielectric properties of PAE, solubility and film-forming properties. Meanwhile BCB groups can be polymerized or crosslinked to form a new polymer, it has a higher molecular weight and cross-linked network structure, in order to improve the thermal stability of the polymer and solvent resistance.A new fluorinated poly(aryl ether) with reactive benzocyclobutene groups as the side chain was successfully synthesized. This polymer showed a number-average molecular weight(Mn) of 200 000 and had good solubility and film-forming ability. After being postpolymerized at high temperature(>200 °C), the polymer film converted to a cross-linked network structure, which was insoluble in the common organic solvents. Such results suggest that the postpolymerization is an efficient way to achive the balance between the solubility and the solvent resistance of the polymer. TGA data showed that the postpolymerized polymer had a 5 wt % loss temperature at 495 °C and a residual of 61% at 1000 °C under N2. The cross-linked film also exhibited good dielectric properties with an average dielectric constant of about 2.62 in a range of frequencies from 1 to 30 MHz. With regard to the mechanical properties, the cross-linked film had hardness, Young’s modulus, and bonding strength to a silicon wafer of 1.22, 8.8, and 0.89 GPa, respectively. These data imply that this new polymer could be used as a high-performance insulation materials used in the electrical industry, microelectronics industry and the aerospace industry.