A novel fluorinated macromonomer (TFVE-Si) with four functional groups derived from easily available tetraethoxysilane (TEOS) has been successfully synthesized through the Piers–Rubinsztajn reaction using B(C6F5)3 as a catalyst. This procedure efficiently avoids the generation of Si–OH and −Si–CH2–CH2– groups, which greatly affect the properties of the organosiloxanes. Prepolymerizing the macromonomer in mesitylene solution gives an oligomer which can form a flexible and highly transparent free-standing cross-linked polysiloxane film followed by a postpolymerization procedure at high temperature. The cross-linked polysiloxane (thickness = 2 mm) shows a transmittance of higher than 91% in the visible region and an absorbance of near 100% in the UV region (<350 nm), exhibiting its potential application as a transparent coating for blocking ultraviolet rays in both household and industrial uses. In particular, the cross-linked film shows low dielectric constant (Dk) of 2.50 and low dissipation factor (Df) of 4.0 × 10–3 at an ultrahigh frequency of 10 GHz. This is the first example of nonporous polysiloxane having both low Dk and Df while conventional TEOS-based polymers exhibit higher Dk (>3.0). Moreover, D–E loop tests illustrate that the cross-linked polysiloxane possesses excellent linear dielectric properties, further suggesting its good insulating properties. Furthermore, the prepared polysiloxane exhibits high thermostability with a 5 wt % loss temperature of 476 °C and a glass transition temperature (Tg) of 110 °C as well as good mechanical strength (with an elastic modulus of 1.1 GPa). Because of the existence of fluoro-containing groups, the polysiloxane also shows high hydrophobicity. Furthermore, TFVE-Si can efficiently improve the Tg of linear polysiloxane prepared from dimethylsiloxane with two functional groups. These indicate that the fluorinated TEOS has potential application in the microelectronics industry; especially, it can meet the requirement of the high-frequency communication fields for the materials with both low Dk and Df.

A fluorinated and thermo-cross-linked polyhedral oligomeric silsesquioxane (POSS) has been successfully synthesized by thermal polymerization of a fluorinated POSS monomer having an inorganic silsesquioxane core and organic side chains bearing thermo-cross-linkable trifluorovinyl ether groups. This new inorganic–organic hybrid polymer shows high thermostability with a 5 wt % loss temperature of 436 °C, as well as good transparency (a sheet with an average thickness of 1.5 mm shows high transmittance of 92% varying from 400 to 1100 nm). Moreover, the polymer exhibits both low dielectric constant (<2.56) and low dissipation factor (<3.1 × 10–3) in a wide range of frequencies from 40 Hz to 30 MHz even at a high frequency of 5 GHz. The polymer also shows low water uptake (<0.04%) and low Dk (near 2.63) after immersing it in water at room temperature for 3 days. These data imply that this polymer is very suitable to be utilized as a high-performance dielectric material for fabrication of high-frequency printed circuit boards or encapsulation resins for integrated circuit dies in the microelectronic industry. Furthermore, this work also provides a route for the preparation of fluorinated POSS-based polymers.Keywords: dielectric constant; fluoropolymers; high-performance polymers; hydrophobicity; Polyhedral oligomeric silsesquioxane (POSS);

A novel fluoropolymer having triazine rings and thermo-crosslinkable benzocyclobutene units is prepared by a facile phase transfer catalyzed interfacial polycondensation reaction between a diphenol and a dichloro-s-triazine. This is the first example of thermo-crosslinkable fluoropolymer containing triazine units. The polymer shows a high molecular weight (Mn) of more than 70 000, good solubility and film-forming ability, as well as high storage stability. When treated at a high temperature (>200 °C), the polymer easily converts to a crosslinked network, showing a low dielectric constant (Dk) of 2.58 at a range of frequencies from 0.1 to 30.0 MHz. The Dk does not exhibit obvious change as the temperature is raised from room temperature to 100 °C. Moreover, the crosslinked network exhibits a dielectric strength of 157.7 kV cm−1, which is comparable with that of a widely used resin poly(2,6-dimethyl-1,4-phenylene ether). D–E loop tests indicate that the cured polymer possesses linear dielectric properties. The cured polymer also exhibits high hydrophobicity, which endows the polymer with a low water uptake of 0.11% after immersing it in water at room temperature for 72 h. Moreover, the crosslinked network exhibits high thermo-stability with a glass transition temperature of 264 °C and a 5 wt% loss temperature of 426 °C, as well as good mechanical properties with an average hardness of 0.48 GPa and an average Young's modulus of 11.92 GPa. These results suggest that this fluoropolymer having triazine units is better than those prepared from cyanate esters because the new polymer exhibits not only good dielectric properties, high thermostability and low water uptake, but also possesses high storage stability and good processability. Hence, this new fluoropolymer is suitable as a new dielectric matrix resin for the production of printed circuit boards used in the microelectronic industry.

Anethole, a naturally occurring aromatic compound which can be extracted abundantly from plants like star anise, fennel and basil, has been conveniently transformed to a functional monomer in an overall yield of 81% via a two-step procedure. The obtained monomer combines reactive benzocyclobutene and propylene groups, thus it can undergo thermo-polymerization to form a crosslinking network, showing a low dielectric constant (<2.64 in a range of frequencies varying from 0.1 to 30 MHz) and low water uptake (<0.20% in boiling water for 144 h). TGA and DSC data exhibit that the cross-linked network has a 5 wt% loss temperature of 455 °C in N2 and a Tg of 160 °C, respectively. These results indicate that the new polymer based on biorenewable anethole is comparable to the materials derived from petroleum. On the basis of the wide application of low dielectric constant materials in the microelectronic industry, this work would offer a new sustainable feedstock to organic low k materials. Moreover, this contribution also provides a new route to convert other aromatic natural products.

An intrinsically microporous fluoropolymer has been successfully synthesized through thermo-cross-linking of a functional monomer having a quaternary carbon center and thermopolymerizable trifluorovinyl ether groups as the side chains. Because the monomer has a tetrahedral configuration, the thermo-cross-linking produces spontaneously formed micropores with an average size of 8 Å in the polymer. Because of the existence of the micropores, the fluoropolymer exhibits excellent dielectric properties with dielectric constant (Dk) of 2.36 and dissipation factor (Df) of 1.29 × 10–3 at a frequency of 5 GHz. Moreover, the polymer shows very low water uptake (<0.08% in water of 99 °C for 72 h) and high transparency (transmittance of 93% varying from 400 to 1100 nm). TGA and DMA data show that the polymer has 5 wt % loss temperature of 492 °C (in N2) and Young’s modulus of 4.95 GPa, respectively. These results suggest that the polymer is very suitable as the matrix resin for the production of the composites utilized in high-frequency printed circuit boards (HF-PCBs). In particular, this work is the first example for the production of a low Dk and Df polymer using a strategy of spontaneously forming pores. Because HF-PCBs have a broad range of applications, this contribution is of considerable industrial importance.

A propargyl ether-functionalized poly(m-phenylene) (PE-PMP) is reported here. This polymer exhibits good solubility and film-forming ability. After postpolymerization at high temperature, the polymer transforms to a cross-linked network, which shows high thermostability with a 5% weight loss temperature at 471 °C and a char yield of 67% at 1000 °C under N2. Thermo-mechanical analysis (TMA) reveals that the cured polymer shows an average linear coefficient of thermal expansion (CTE) of 30.6 ppm °C−1 ranging from 30 to 300 °C and a glass transition temperature (Tg) near 330 °C. Moreover, even at temperatures up to 300 °C, the cured polymer possesses a storage modulus exceeding 4.0 GPa. These data are superior to those of the commercial epoxy and novolac resins and polyimides. Furthermore, the cured polymer film has good mechanical properties with hardness, Young's modulus and a bonding strength to a silicon wafer of 1.22, 9.44 and 0.78 GPa, respectively. The cured polymer film also shows good dielectric properties with an average dielectric constant of 2.93 in a range of frequencies from 2 MHz to 30 MHz. Such results suggest that the polymer is a useful precursor for preparation of insulating materials with high modulus and Tg in the microelectronics industry.