One-step preparation of efficient cuprous chloride catalyst for direct synthesis of trimethoxysilane

CuCl-based catalysts are the most commonly used catalysts for the“direct synthesis”of trimethoxysilane(M3).CuCl species are sensitive to air and water,and are prone to oxidation deactivation.When CuCl is directly used as a catalyst,it needs to be purified before the utilization,and the operating conditions for the catalyst preparation are relatively harsh,requiring the inert gas environment.Considering a high-temperature activation step required for CuCl-based catalysts used for catalyzing synthesis of M3 to form active phase Cu–Si alloys(Cu_(x)Si)with Si powder,in this work,a series of catalysts for the“direct synthesis”of M3 were obtained by a one-step high-temperature activation of the mixture of stable CuCl_(2) precursors,activated carbon-reducing agent,and Si powder,simultaneously achieving the reduction of CuCl_(2) to CuCl and the formation of active phase Cu_(x)Si alloys of CuCl with Si powder.The prepared samples were characterized through various characterization techniques,and investigated for the catalytic performance for the“direct synthesis”of M3.Moreover,the operation conditions were optimized,including the activation temperature,catalyst dosage,Si powder particle size,and reaction temperature.The characterization results indicate that during the one-step activation process,the CuCl_(2) precursor is reduced to CuCl,and the resulting CuCl simultaneously reacts with Si powder to form active phases Cu3Si and Cu15Si4 alloys.The optimal catalyst Sacm(250,0.8:10)exhibits a good catalytic activity with selectivity of 95%and yield of 77%for M3,and shows a good universality for various alcohol substrates.Furthermore,the catalytic mechanism of the prepared catalyst for the“direct synthesis”of M3 was discussed.

Preparation and characterization of 3-mercaptopropyl trimethoxysilane self-assembled monolayers

Silane coupling regent （3-mercaptopropyl trimethoxysilane （MPTS）） was prepared on the single-crystal silicon substrate to form 2-dimensional self-assembled monolayers （SAMs）. The growth behavior of SAMs formed from 3-MPTS was investigated using atomic force microscopy （AFM）, contact angle measurements, ellipsometry, and X-ray photoelectron spectroscopy （XPS）. The formation behavior of MPTS SAMs was investigated by a series of AFM images and the roughness of MPTS SAMs on silicon substrates with the assembling time from 1 min to 24 h. The water contact angle measurements indicated the growth behavior of MPTS that correlated with the AFM measurements at different immersion times, too. The chemical states of the typical elements in the MPTS SAMs were analyzed using X-ray photoelectron spectroscopy. The results show that MPTS is self-assembled on the substrate.

Highly-selective Pt/PAA@MIL-125 Catalyst for Hydrosilylation of γ-(2,3-Epoxypropoxy) Trimethoxysilane

γ-(2,3-Epoxypropoxy)trimethoxysilane is a crucial silicone product synthesized by hydrosilylation.Its derived downstream silicone products have galvanized the development of silicone industry.However,the Speier's or Karstedt's catalysts commonly utilized in its industrial process are homogeneous,leading to complications,such as low catalytic selectivity and recycling difficulty.Herein,a new heterogeneous platinum catalyst was developed by using a titanium-based metal organic framework(MIL-125)composite with polylactic acid(PAA)as the support.The as-synthesized Pt/PAA-2@MIL-125 catalyst exhibited impressive catalytic performance,producing a 97%yield inβ-product,and maintained recyclability for the synthesis ofγ-(2,3-epoxypropoxy)trimethoxysilane.Further characterization analyses revealed that the introduction of PAA resulted in the formation of a defective mesoporous MIL-125,which accelerated the transmission efficiency of reactants.Moreover,the abundant carboxylic acid groups in the MIL-125/PAA composite could interact strongly with Pt active species,thereby enhancing the catalytic performance and minimizing the loss of Pt,ultimately improving its cycling performance.The comprehensive experiments demonstrated the potential of this catalyst as an effective and versatile heterogeneous catalyst not only for the hydrosilylation of various olefins,but also for the hydrosilyation of silanes.

Nano-indentation profiles of intrinsic hardness and modulus of films based on silsesquioxane modified with titanium tetrabutoxide

This study is to analyze the influence of the modifier, 5～25 wt % titanium tetrabutoxide (TBO), on the hardness and elastic modulus of the films based on SSO deriving from hydrolytic condensation of (3-glycidoxypropyl)trimethoxysilane (GPMS) and vinyltrimethoxysilane (VMS), by the continuous stiffness measurement (CSM) technique of an instrumented-indentation testing (IIT) device. Films were synthesized by adding the stoichiometric amount of ethylenediamine (EDA) and benzoyl proxide (BPO) to SSO solutions in ethanol, dip-coating over glass substrates, and curing using an appropriate thermal cycle. Intrinsic values of hardness and elastic modulus were determined with the average values in “plateau region” from “four-layer” explanation. And the brittle index of the modified coating systems was analyzed.

SYNERGETIC EFFECTS OF SILANE-GRAFTING AND EVA ON WATER TREE RESISTANCE OF LDPE

The synergetic influence of silane-grafting and polar additives （EVA） on the water tree resistance of the low density polyethylene has been investigated. A series of samples obtained before and after hydration have been characterized by measuring gel content, infrared spectroscopy （FTIR）, differential scanning calorimetry （DSC） and dielectric measurements. The results obtained clearly show that the silane condensation occurred and that the silane-grafting and polar additives have synergetic effects on the water tree resistance of LDPE with little influence on its dielectric properties, e.g. the dielectric breakdown strength, dielectric permittivity and loss tangent.

Self-Assembled Monolayer of Mixed Gold and Nickel Nanoparticles

Forming a monolayer of mixed nickel and gold nanoparticles through self-assembly via simple solution processing constitutes an important step toward inexpensive nanoparticle-based carbon nanofiber growth.In this work,mixed gold and nickel nanoparticles were anchored on the silicon wafer using self-assembled monolayers(SAMs)as a template.SAMs of 3-mercaptopropyl trimethoxysilane(MPTS-SAMs)were formed on silicon wafer,with the exposed thiol functionality providing ligand exchange sites to form the mixed monolayer of nickel and gold nanoparticles via a two-step sequential soaking approach.The densities of the nickel and gold nanoparticles on the surface can be varied by adjusting the soaking sequence.

Influence of POSS modifier on NLO properties of the hybrid materials

The nonlinear optical （NLO） active chromophore was prepared bv a bridging agent, glyeidyl ether （ AGE）, to connect disperse orange 3 （ DO3 ） and （ γ-Methaerylpropyl）-silsesquioxane （MP-SSO）. A freeradical polymerization was performed to fabricate the methacrylate/Silica hybrid NLO films. Different amounts （ 5-25 wt% ） of （γ-methacrylpropyl） -polyhedral oligomeric silsesquioxanes （POSS） were added as the modifier to improve the degree of cross-linking, density and structure of the NLO matrix. As a result, the modified material properties including coating transmittance, glass transition temperature （ Tg ） , absoption spectra before and after poling, Marker stripes, etc. were presented. The hybrid film containing 15 wt% POSS exhibits the highest T, nonresonant second-order nonlinearity （d33 = 92 pro/V） and temporal stability among the others.

Spectrophotometric Characterization of the Complex Generated in Solution for the Reaction of H[Ru(III)Cl₂(H₂EDTA)] Complex with AETS Modifier Agent

Spectrophotometric method was used to evaluate the kinetic of the complex formation from the reaction between H[Ru(III)Cl2(H2EDTA)] and the modifier agent [3-(2-aminoethyl)aminopropyl] trimethoxysilane (AEATS) (μ = 0.50 mol.dm-3 with NaCF3COO, 298.15 K), in pseudo-first order conditions. These studies showed that the reactions are successives producing several species influenced by the concentrations ratio. The electronics spectrum of all solutions showed a band in 457 nm with variable molar absorptivity (ε).

Graphene-templated approach to ultrathin silica nanosheets

Graphene,a perfect two-dimensional (2D) nanostructure,is an ideal template for 2D material design.We developed a graphenetemplated method to synthesize 2D silica nanosheets through the crosslinking of poly(3-methacryloxypropyl trimethoxysilane)grafted graphene oxide (GO-g-PMPS),followed by pyrolysis at 700℃ for 10 h.