Novel heat resistant methyl-tri(phenylethynyl)silane resin: Synthesis, characterization and thermal properties

High-Temperature Resistant Polyborosilazanes with Tailored Structures

Boron-containing organosilicon polymers are widely used under harsh environments as preceramic polymers for advanced ceramics fabrication. However, harmful chemicals released during synthesis and the complex synthesis routes have limited their applications. To solve the problems, a two-component route was adopted to synthesize cross-linked boron-containing silicone polymer (CPBCS) via a solventless process. The boron content and CPBCSs’ polymeric structures could be readily tuned through controlling the ratio of multifunctional boron hybrid silazane monomers (BSZ12) and poly[imino(methylsilylene)]. The CPBCSs showed high thermal stability and good mechanical properties. The CPBCS with Si-H/C=C ratio of 10:1 showed 75 wt% char yields at 1000 °C in argon, and the heat release capacity (HRC) and total heat release (THR) are determined to be 37.9 J/g K and 6.2 KJ/g, demonstrating high thermal stability and flame retardancy. The reduced modulus and hardness of CPBCS are 0.30 GPa and 2.32 GPa, respectively. The novel polysilazanes can be potentially used under harsh environments, such as high temperatures or fire hazards.

Study on Properties of Heat-Resistant Hybrid Resin Containing Silicon and Composites

In recent years, one kind of novel hybrid polymer containing silicon has already been reported in the field of high-temperature resistance polymer. Gradually, it has been a research hotspot in the field of high-performance matrix resins because of excellent heat resistance and dielectric properties. The composite was prepared by M-aminophenylacetylene terminated polymethyldiphenylethynyl silane (MDPES-2) as a matrix and nonalkali glass cloth as reinforced material using a hot press process. The cure reaction of MDPES-2 was characterized. Meanwhile, heat resistance, mechanical properties, and dielectric properties of MDPES-2 composites were systematically studied in this paper. The results showed that flexural strength at room temperature is 321 MPa and flexural strength retention at 240°C was 98.3%. Flexural strength retention after thermal treatment at 500°C for 7 min was 84%. In addition, $\epsilon$ and dielectric dissipation factor ( $\tan \delta$ ) were 3.9 and $2.0\times {10}^{-3}$ (10 GHz).

Mechanistic investigation of zinc-promoted silylation of phenylacetylene and chlorosilane: a combined experimental and computational study

The zinc-promoted silylation method is of great importance to synthesize high-performance silicon-containing arylacetylene (PSA) resins in the industry. However, it is difficult to eliminate the accompanied by-product of terminal alkenes due to the lack of mechanistic understanding of the silylation. The initiation of zinc-promoted silylation is facilitated by the interaction between zinc and phenylacetylene. Our DFT calculations indicated that the intermolecular hydrogen transfer of phenylacetylene follows an ionic pathway, which generates a phenylacetylene anion and the corresponding alkene moieties on the zinc surface. The styrene by-product is observed in this stage, with its alkene moieties desorbing as radicals into the solvent under the high reaction temperature. Three possible intermediates of surface phenylacetylene anions were proposed including PhC[triple bond, length as m-dash]C-Zn, PhC[triple bond, length as m-dash]CZnCl, and (PhC[triple bond, length as m-dash]C)2Zn. These carbanion-zinc intermediates undergo an SN2 reaction with Me3SiCl to afford the alkynylsilane on the zinc surface, which is calculated to be the rate-determining step for the zinc-promoted silylation reaction.

Star-shaped arylacetylene resins derived from silicon

Star-shaped arylacetylene resins, tris(3-ethynyl-phenylethynyl)methylsilane, tris(3-ethynyl-phenylethynyl) phenylsilane, and tris (3-ethynyl-phenylethynyl) silane (TEPHS), were synthesized through Grignard reaction between 1,3-diethynylbenzene and three types of trichlorinated silanes. The chemical structures and properties of the resins were characterized by means of nuclear magnetic resonance, fourier-transform infrared spectroscopy, Haake torque rheomoter, differential scanning calorimetry, dynamic mechanical analysis, mechanical test, and thermogravimetric analysis. The results show that the melt viscosity at 120 °C is lower than 150 mPa⋅s, and the processing windows are as wide as 60 °C for the resins. The resins cure at the temperature as low as 150 °C. The good processabilities make the resins to be suitable for resin transfer molding. The cured resins exhibit high flexural modulus and excellent heat-resistance. The flexural modulus of the cured TEPHS at room temperature arrives at as high as 10.9 GPa. Its temperature of 5% weight loss (T d5) is up to 697 °C in nitrogen. The resins show the potential for application in fiber-reinforced composites as high-performance resin in the field of aviation and aerospace.

Synthesis and characterization of highly oxidative resistant silicon–acetylene hybrid resin grafted with modified mesoporous silica

This study focused on the preparation and characterization of silicon–acetylene resin by means of grafting functionalized mesoporous silica. (3-Aminopropyl) triethoxysilane was grafted to silica surface through the hydrolysis reaction to yield mesoporous silica functionalized with (3-Aminopropyl) triethoxysilane (MA). These MA nanoparticles were transferred to the chain of silicon–acetylene resin, poly(m-dietheynylbenzene-methylsilane) (PSA) to yield PSA-g-MA, with the help of the reaction of hydrochloric acid removal. PSA-g-MA was totally characterized by Fourier transform infrared spectroscopy, energy dispersive spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscope, transmission electron microscope, and nuclear magnetic resonance, which certified the success of silica modification and functionalized nanoparticles grafted to chain of PSA. The char content of PSA-g-MA reached to 45% at 1000°C under air atmosphere, and the residual weight was increased by nearly 10%, compared with the unmodified PSA.

A novel boron–silicon–alkynyl hybrid copolymer

A novel boron–silicon–alkynyl hybrid copolymer (BSD) was synthesized by condensation polymerization of 1,3-diethynylbenzene with dichloromethylsilane and boron trifluoride etherate. Fourier transform infrared and 1H-, 13C-, and 29Si-nuclear magnetic resonance spectroscopies were used to confirm the structures of the copolymers. Thermogravimetric analysis and differential scanning calorimetry showed that the polymer exhibited excellent heat resistance and thermo-oxidative stabilities under nitrogen and air. The cure cross-linking reaction mechanisms of the BSD were related to Diels–Alder intermolecular cyclization involving two C≡C bonds and hydrosilylation reaction between Si–H and C≡C bonds. The [Formula: see text] of the BSD was above 591°C and 530°C under nitrogen and air, respectively. The residues at 1000°C were above 88% under nitrogen and 25% in air. X-ray diffraction was used to study the formation of ceramics. The precursor for ceramics (β-SiC, α-SiC, and B4C) was formed at 1600°C under an argon atmosphere. The thermo-oxidative stabilities of the copolymers were attributed to the existing organic groups of alkynyl and inorganic elements of silicon and boron.

Synthesis, thermal properties, and ceramization of a novel ethynylaniline-terminated polysilazane

A novel ethynylaniline-terminated polysilazane (PCSN) was synthesized from the ammonolysis reaction of dichloromethylsilane (MeSiHCl2) and p-phenylenediamine, by which terminal ethynyl groups were introduced into the resultant PCSN. Different average molecular weight PCSNs obtained with adjusting the molar ratios between p-phenylenediamine and MeSiHCl2 were used to investigate the influence of average molecular weights and contents of terminal ethynyl groups on thermal properties and ceramic conversions of PCSNs. The structure of PCSN was characterized using Fourier transform infrared, proton, carbon-13, and silicon-29 nuclear magnetic resonance spectroscopies. Among all the PCSN precursors, PCSN-4 has the lowest curing temperature (237.1°C) and the highest enthalpy (863.0 J g−1) because of its highest content of terminal ethynyl groups, improving its cross-linking. The thermal properties of cured PCSN were studied by means of thermogravimetric analysis under nitrogen atmosphere. The collaborative effect from both the average molecular weight and the contents of terminal ethynyl groups gave PCSN-3 the best thermal stability. The temperature of 5% mass loss was 564°C and the residual mass at 900°C was 84.4%. After sintering at 1450°C in argon atmosphere, PCSN-3 thermoset turned into black solids composited of β-silicon carbide (β-SiC), α-silicon nitride, α-SiC, and free carbon with a yield of 78.4%, indicating PCSN had the potential to be used as ceramic precursors.

Highly heat resistant and thermo-oxidatively stable borosilane alkynyl hybrid polymers

A type of boron–silicon containing hybrid polymer with CC units (HBS) was prepared, and the effects of three different substituents on the properties of the polymers were studied.

Synthesis, NMR characterization and reactivity of 1-silacyclohex-2-ene derivatives

The chloro functionality of allyldichlorosilane (HSiCl2(C3H5)) and allyldichloromethylsilane (MeSiCl2(C3H5)) were replaced by alkynyl groups and new compounds, allyldialkynylsilane 1 and allyldialkynylmethylsilane 2, were obtained. These silanes, which served as starting materials for the onward reactions, were purified by fractional distillation. They were further subjected to hydroboration with 9-BBN (9-borabicyclo[3.3.1]nonane) and were converted into 1-silacyclohex-2-ene derivatives 5 and 6. The competition between C≡C and C=C in the reaction was studied. The hydroborating reagent 9-BBN was expected to prefer terminal C=C bonds and to leave C≡C bond untouched. This hypothesis of preferable hydroboration was experimentally proved, and hence, 1-silacyclohex-2-ene derivatives were obtained in reasonably pure form. The reaction of allyldialkynylsilane 2 with one equivalent of 9-BBN affords 1-silacyclohex-2-ene bearing Si-C≡C-function, ready to be hydroborated further with one equivalent of 9-BBN. The obtained compound bears two C-B bonds, which are attractive synthones for further transformations. This study aims to highlight the chemistry of C-B and Si-H functional groups. All new compounds obtained were colorless air and moisture sensitive oils, and they were studied by multinuclear magnetic resonance spectroscopy (1H, 13C, 11B, 29Si NMR) in solution.