A New Fluorinated Polysiloxane with Good Optical Properties and Low Dielectric Constant at High Frequency Based on Easily Available Tetraethoxysilane (TEOS)

Abstract

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 (D k ) of 2.50 and low dissipation factor (D f ) of 4.0 × 10–3 at an ultrahigh frequency of 10 GHz. This is the first example of nonporous polysiloxane having both low D k and D f while conventional TEOS-based polymers exhibit higher D k (>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 (T g) 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 T g 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 D k and D f .

Synthesis of Silphenylene-Containing Siloxane Resins Exhibiting Strong Hydrophobicity and High Water Vapor Barriers

“…Furthermore, the strong signals observed between −1 and −2 ppm corresponded to the silphenylene units of the silphenylene-siloxane resin, as confirmed by literature studies [26,27]. Moreover, the T 3 structure of the silphenylene-silicone resin was clearly revealed in the low phase signal groups (−77.67 and −79.56 ppm) in the 29 Si spectrum. The obtained NMR results therefore confirm that VPSSP can be successfully prepared via the described hydrolytic polymerization process.…”

“…Fourier transform infrared (FT-IR) measurements were conducted on a Spectrum 100 infrared spectrometer (Perkin-Elmer, Fremont, CA, USA) at room temperature (25 • C) at 4000-450 cm −1 . The refractive indices were measured using a WZS-1 refractometer (Shanghai Optical Instrument Factory, Shanghai, China) at 25 • C. 1 H NMR (400 MHz, CDCl 3 , TMS) and 29 Si NMR (79 MHz, CDCl 3 ) spectra were recorded using a Bruker AVANCE AV 400 MHz spectrometer (Bruker Co., Karlsruhe, Germany) at room temperature. Gel permeation chromatography (GPC) was carried out on a Waters 1525/2414 chromatograph (Waters Co., Milford, MA, USA) in a linear column eluted with tetrahydrofuran at a flow rate of 1.0 mL/min.…”

New Control Over Silicone Synthesis using SiH Chemistry: The Piers–Rubinsztajn Reaction

“…The relative lack of reactivity of alkene, alkyne and haloalkyl‐modified silicones under PR conditions allows these groups to be used in orthogonal organic processes to construct macromolecular systems. For example, polymers of fluorocarbons and silicones were shown to result from sequential PR reactions and then thermolysis to facilitate 2+2 cycloadditions with perfluoroalkenes to give linear or crosslinked polymers (Figure A) . Rambarran et al.…”

“…For example, polymers of fluorocarbons and silicones were shown to result from sequential PR reactions and then thermolysis to facilitate 2 + 2c ycloadditions with perfluoroalkenes to give linear or crosslinked polymers ( Figure 9A). [47] Rambarran et al showed that, following the PR reaction,H uisgen or azide/alkyne click reactions could be used to create silicone/PEG (or cyclodextrin) surfactants (Figure 9B), [48] elastomers ( Figure 9C), [49] copolymers [50] or adhesives. [51] The most important orthogonal reaction in silicone systemsisp latinum-catalyzed hydrosilylation (see below).…”

Synthesis of polysiloxanes containing trifluoroethylene aryl ether groups: The effect of promoters

“…PFCB polymers are mainly prepared by the [2π + 2π] thermocyclization of trifluoroethylene aryl ether (TFVE) monomer . Recently, PFCB polymers have attracted extensive attention of researchers in various fields including electronics industry, aerospace, fuel cells, optical waveguide materials, and coatings because of the unique properties such as low dielectric property, low hygroscopicity, high thermal stability, chemical solvent resistance, and low birefringence. However, most of the research interests are focused on the functionality of PFCB group.…”