Si-OR Groups Research Articles

Inundative practice for screening siRNA management candidates against a notorious predatory beetle using olfactory silencing

Calosoma maximoviczi, a predatory pest beetle, poses a significant threat to wild silk farm production due to its predation on wild silkworms. Given the coexistence of this species with beneficial silkworms in the farm orchards, chemical pesticides are not an ideal solution for controlling its population. In this study, we employed a comprehensive multi-target RNA interference (RNAi) approach to disrupt the olfactory perception of C. maximoviczi through independently silencing 16 odorant receptors (ORs) in the respective genders. Specifically, gene-specific siRNAs were designed to target a panel of ORs, allowing us to investigate the specific interactions between odorant receptors and ligands within this species. Our investigation led to identifying four candidate siOR groups that effectively disrupted the beetle's olfactory tracking of various odorant ligands associated with different trophic levels. Furthermore, we observed sex-specific differences in innate RNAi responses reflected by subsequent gene expression, physiological and behavioral consequences, underscoring the complexity of olfactory signaling and emphasizing the significance of considering species/sex-specific traits when implementing pest control measures. These findings advance our understanding of olfactory coding patterns in C. maximoviczi beetles and establish a foundation for future research in the field of pest management strategies.

A catalyst- and additive-free synthesis of alkoxyhydrosiloxanes from silanols and alkoxyhydrosilanes.

A convenient method for the selective synthesis of alkoxyhydrosiloxanes that bear SiH and SiOR2 groups on the same silicon atom, R13Si-O-SiR32-n(OR2)nH (n = 0, 1, or 2), via a simple catalyst- and additive-free dealcoholization reaction between silanols and alkoxyhydrosilanes has been developed. These alkoxyhydrosiloxanes can be easily converted into Si(OR2)3-containing siloxanes by zinc catalyzed alkoxylation and alkoxy-containing silphenylene polymers by platinum catalyzed hydrosilylation.

Selective Formation of Alkoxychlorosilanes and Organotrialkoxysilane with Four Different Substituents by Intermolecular Exchange Reaction.

Alkoxychlorosilanes are scientifically and industrially important toward preparing silicone and silica as well as preparation of siloxane-based nanomaterials by stepwise reactions of Si-OR (R=alkyl) and Si-Cl groups. Intermolecular exchange of alkoxy and chloro groups between alkoxysilanes and chlorosilanes (functional group exchange reaction) provides an efficient and environmentally benign route to alkoxychlorosilanes. BiCl3 as a Lewis acid catalyst can promote the functional group exchange reactions more efficiently than conventional acid catalysts. Higher reactivity has been observed for chlorosilanes with smaller numbers of Si-CH3 groups and for alkoxysilanes with larger numbers of Si-CH3 groups. The reaction mechanism is proposed and selective syntheses of alkoxychlorosilanes are demonstrated. These findings also enable us to synthesize an organotrialkoxysilane with four different substituents.

Polymerization of hybrid organic–inorganic materials from several silicon compounds followed by TGA/DTA, FTIR and NMR techniques

Abstract Hybrid organic–inorganic films have been prepared by hydrolysis and condensation of several silicon compounds: 3-methacryloxypropyltrimethoxysilane (MPTS) or methyltriethoxysilane (MTES) and tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) precursors using four [TEOS] or [TMOS]/[MPTS] or [MTES] molar ratios: 0, 0.5, 1 and 2. The progress on the organic and inorganic polymerizations was followed employing thermogravimetric analysis (TGA), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), 13 C and 29 Si nuclear magnetic resonance (NMR). These techniques have provided information about the hybrid network formation inside films. The formation of the hybrids prepared from [TEOS]/[MPTS] and [TMOS]/[MPTS] mixtures was accomplished through the reaction of Si OR groups, via condensation of silanols (inorganic condensation), and opening of the C C double bond in MPTS (organic polymerization). The formation of the hybrids prepared from [TEOS]/[MTES] and [TMOS]/[MTES] mixtures was mainly accomplished through the reaction of Si OR groups. The increment of TEOS or TMOS in MPTS mixtures favored the inorganic (Q 3 and Q 4 units) condensation. Total degrees of condensation for hybrids synthetized with [TEOS] or [TMOS]/[MTES] were higher than those obtained with [TEOS] or [TMOS]/[MPTS], so MTES favored the formation of hybrids with branched organic structures.

Synthesis and properties of siloxane-crosslinked polyurethane-urea/silica hybrid films from castor oil

A novel hybrid diol (HD) crosslinker has been synthesized with hydrolyzable –Si–OR groups from 3-amino propyl trimethoxy silane and 3-glycidoxy propyl trimethoxy silane. Its chemical structure was confirmed by Fourier transform infrared spectroscopy, 1H and 13C nuclear magnetic resonance spectroscopy to introduce it as a crosslinker in the castor oil, a renewable resource, to develop functional organic inorganic hybrid coatings. A series of castor oil-based organic–inorganic hybrid materials were prepared from castor oil, isophorone diisocyanate, and the different weight percentages of synthesized HD. Dynamic mechanical thermal analysis, thermogravimetric analysis, differential scanning calorimetry, and the universal testing machine were employed to characterize the hybrid films. The measured properties were found to be strongly influenced by the weight ratio of HD to the castor oil-based polyurethanes. The glass transition temperatures (Tg) for the cured hybrid films were found to be 26–72°C. Antibacterial activity, in vitro hydrolytic degradation, and swelling properties of the hybrid films have been studied. The cured hybrid films exhibited excellent antibacterial activity, which was enhanced with addition of the HD. The alkoxy silane-crosslinked castor oil-based coatings have shown better mechanical and viscoelastic properties in comparison to the control (uncrosslinked castor oil-based polyurethane-urea) coatings. The results showed that the weight percent of the HD is the main factor that controls the thermal, antimicrobial, mechanical, swelling, and degradation properties of these hybrid films.

Adsorption in Periodically Ordered Mesoporous Organosilica Materials Studied by in Situ Small-Angle X-ray Scattering and Small-Angle Neutron Scattering

Modified periodically ordered mesoporous organosilica materials were prepared starting from a recently introduced type of sol-gel precursor, containing both organic moieties and hydrolyzable Si-OR groups. In order to thoroughly characterize the mesoporosity and its accessibility, different probe gases were used in conventional gas adsorption experiments. Furthermore, in situ small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) were applied to study the mesoporosity and the sorption processes, taking advantage of scattering contrast matching conditions. Thereby, the materials were characterized not only by different probe molecules but also at different temperatures (nitrogen at 77 K, dibromomethane at 290 K and perfluoropentane at 276 K). The comparison between the standard and in situ SAXS/SANS adsorption experiments revealed valuable information about the porosity and microstructure of the materials. It is demonstrated that the organic moieties are homogeneously distributed; that is, they do not phase-separate from silica on the nanometer scale.

Preparation and characterization of polyimide–nanogold nanocomposites from 3-mercaptopropyltrimethoxysilane encapsulated gold nanoparticles

In this study, we report a new design to prepare polyimide–nanogold nanocomposites of high Au content and good thermal stability. The nanocomposites were prepared from the coupling agent (3-aminopropyltriethoxysilane, APS) capped poly(amic acid) (PAA–APS) and 3-mercaptopropyltrimethoxysilane (MPS) stabilized gold nanoparticles (MPS–Au). The Si–OR groups of MPS on the surface of MPS–Au provided further reaction with APS, hence the covalent bonds between PAA and MPS–Au were formed. PAA–Au was converted into PI–Au nanocomposite by a multiple-step baking. The results of particle-sized analysis show that the sizes of the synthesized MPS–Au from different MPS/Au mole ratios (2 and 0.5) are about 2 nm and 5 nm, respectively. FE-SEM images show that MPS–Au particles are dispersed well in the prepared nanocomposites and no large-scale aggregation occurs. TGA results indicate that the decomposition temperature of each nanocomposite prepared from its washed precursor is lower than that of APS-capped polyimide, but the temperature of maximum decomposed rate of each nanocomposite is higher than that of APS-capped polyimide. The results show the high thermal stability and application potentials of the prepared polyimide–nanogold nanocomposites.

Features of fumed silica coverage with silanes having three or two groups reacting with the surface

Fumed silicas modified by 3-methacryloyloxypropyltrimethoxysilane (MAPTMS), methacryloyloxymethylenemethyl diethoxysilane (MMDES), and 3-aminopropyltriethoxysilane (APTES) were studied by means of TPD-DTG, IR, 1H NMR, electrophoresis, photon correlation spectroscopy, and theoretical methods. The modification of fumed silica by these silanes strongly changes the ζ(pH) potential and the particle size distribution in aqueous suspensions depending on the amounts and the structure of a modifier. MMDES gives the better results in comparison with its mixture with APTES or individual MAPTMS in order to reduce the particle (agglomerate) size of modified silica at the modifier concentrations over the 0.05–0.2 mmol/g range. Grafted silanes reduce the hydrophilic properties of silica depending on the pretreatment conditions. Bound MMDES diminishes the ζ potential in contrast to MAPTMS, which markedly magnifies negative ζ potential at pH>5 due to large amounts of residual SiOR groups hydrolysed in the suspensions.

Polyethersulfone-[silicon oxide] hybrid materials viain situ sol-gel reactions for tetra-alkoxysilanes

Polyethersulfone (PES)–[silicon oxide] hybrids were derived via sol–gel reactions for tetraethoxysilane (TEOS) and tetramethoxysilane (TMOS) in dimethylacetamide solutions of the polymer. In one scheme, water was initially present, and condensation reactions between SiOR groups competed with their reactions with —OH groups at PES chain ends. In a second scheme, water addition was delayed; TMOS molecules reacted with chain ends before competing TMOS–TMOS reactions occurred. A third study involved parallel experiments, as follows: 1) introduction of EtOH to PES–TEOS solutions for a time before water addition; and 2) reactions occurring for a time in non-EtOH-containing PES–TEOS solutions before water addition. Infrared (IR) spectroscopy uncovered signatures of Si–O–Si bridges in silicon oxide phases and PES endgroup modifications (Si–O–Ph). Composites prepared according to the latter two schemes contain more Si–O–Ph linkages than those generated via the first. Differential scanning calorimetry showed that Tg can be raised, and thermogravimetric analysis revealed how the PES thermal degradation profile can be modified via these inorganic incorporations. The schemes for late water addition produced composites having increased elongation-to-break and lowered strength relative to unfilled PES. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1799–1810, 1998

Chemical modification of a Nafion ® sulfonyl fluoride precursor via in situ sol-gel reactions

The melt-processible sulfonyl fluoride precursor of a Nafion ® ionomer was utilized as a sol gel reaction medium for 3-aminopropyltriethoxysilane (APrTEOS). The diffusion-mediated reaction of APrTEOS with SO 2F groups can be controlled with high degree of reaction. Fourier transform infra-red/attenuated total reflection studies show that sulfonamide linkages are formed and condensation reactions of SiOR groups provide covalent crosslinking of chains. Formic acid treatment plus high temperature plus long time resulted in a high degree of polymer crosslinking as seen in 29Si solid state nuclear magnetic resonance spectra. Mechanical modulus and strength increase, and elongation-to-break decreases with increasing filler. Hybrids with < 18% uptake accumulate cracks with crosslinked outer layers, each event signalled by a drop in stress followed by stress recovery. While there are sharp visual material fronts inward from both surfaces, EDAX (energy dispersive analysis of X-rays) showed that there are no sharp Si composition boundaries. Differential scanning calorimetry (d.s.c.) revealed a broad, weak endothermic event peaking at 67°C for the precursor and shifting to higher temperatures while broadening with increasing filler content, indicating progressively-restrictive glass-transition-temperature-related molecular motions within an increasingly nonhomogeneous environment. For the unreacted precursor, this d.s.c. transition occurs at a temperature just above a glass transition detected by dynamic mechanical means.

Sol-gel synthesis of SiO 2P 2O 5 glasses

The synthesis of P 2O 5SiO 2 glasses from solutions has been studied through gelation kinetics, Raman and nuclear magnetic resonance (NMR) spectroscopies. Different preparation methods are compared. The effect of the phosphorus precursor has been investigated. Phosphoric acid esters are not hydrolyzed and they do not yield condensation with silica. Reaction of anhydrous H 3PO 4 with SiOR groups leads to the formation of SiOP bonds which are easily hydrolyzed. Only a few remain after addition of water and gelation. Therefore, PSi homogeneity is difficult to achieve after gelation and the following drying and heat-treatment procedures. This absence of homogeneity is observed by solid-state magic angle spinning (MAS)-NMR and X-ray diffraction studies performed on gel samples heated at 300, 500 and 800°C in the case of xerogels and 500, 950 and 1140°C for aerogels.

Study of unimolecular reaction mechanism on silica surface

The thermodestruction mechanism of SiOR(R is CH 3 for A, CHO for B, and COCH 3 for C) groups on the aerosil surface has been investigated by quantum-chemical modified neglect of differential overlap and AM1 methods, IR spectroscopy, mass spectrometry and Rice—Ramsperger—Kassel—Marcus (RRKM) theory. It was found that the thermostability reason of A is due to the high activation energy: E A = E C+60 = E B+70 = 250 kJ mol −1, and stronger reaction entropic hindering: the Arrhenius prefactor is k A = k B/10 = 10 11 s −1. The decomposition probability of A is W CH 2O = 100 W CO,H 2 > W C 2H 4 at 900 K. The destraction of B and C proceeds preferably through a channel with a recovery of SiOH groups and CO or CH 2CO elimination, and the probability of forming SIR′ (R′ B,C  H, CH 3, OCH 3) is less than 10 −6. The prefactors (RRKM) are in the range of experimental k 0, and low depends of decomposition product pressure and temperature. From the results obtained it follows that the main energy flow per functional group arises from a solid at the expense of interacting with phonons.

High Pressure Raman Study of the Hydrolysis Reaction of Tmos and Teos

ABSTRACTHigh pressure Raman spectroscopy is used to monitor the hydrolysis reaction of TMOS in solutions with methanol, acetonitrile, acetone, dioxane and formamide, and of TEOS as a function of pH and the catalyst used. The rate constants for various solvents, temperatures and pressures are experimentally determined from the time dependence of Raman band intensities. It is shown that the reaction is slow in dioxane and fast in methanol or formamide. The volume of activation is found from the pressure dependence of the rate constant. The volume of activation, the dielectric constant, dipole moments and hydrogen bonding properties and their role in the hydrolysis reaction are discussed. It is shown that solvents which can form hydrogen bonding with Si-OR groups can increase the rate of the reaction.

Gels from a double alkoxide: (BuO)2-Al-O-Si-(OEt)3

NMR study (27Al,29Si) of the double Si-Al precursor (BuO)2Al-O-Si(OEt)3 in alcoholic solution shows molecular associations resulting from acid-base interactions with O → Al ≡ bondings. Gels have been prepared in the H2O, HOiPr, (BuO)2Al-O-Si(OEt)3 ternary phase diagram for a large range of oxide concentrations. For all the compositions, the very fast hydrolysis of Al-OR groups leads to an amphoteric sol. Nevertheless, the gelation time is governed by the initial water concentration, showing that the hydrolysis of Si-OR groups is the rate-determining process for the gelation. The apparent activation energy is about 20 kcal mol−1. The relative hardness of gels increases when increasing the precursor concentration. After drying, the oxide skeleton of the xerogel is relatively dense, but the open porosity remains high up to about 1000° C. At this temperature, samples turn into optically clear and dense glass-ceramics, formed of mullite crystallites in amorphous silica.

Gelation study of alumino-silicates by small-angle neutron scattering

We present results concerning the structure of clusters and the kinetics of aggregation obtained by SANS for different compositions in the H2O, HOiPr, (BuO)2Al-O-Si(OEt)3 system.Information about the growth kinetics has been obtained from the time dependence of the Guinier radius, of the maximum intensity on the scattering curve and of the integral of the intensity over the reciprocal space. We observe, in agreement with 29Si NMR data, that the hydrolysis of the Si-OR groups is the rate-determining process for the polymerization.Information about the internal structure of the structure of the clusters has been obtained from the Porod slope, and about the particle interactions by calculation of the structure factor S(Q). Before the gel point, we observe mass-fractal particles characterized by a fractal dimension of 1.9, in agreement with the existence of a cluster-cluster aggregation mechanism during the gelation.The scattering curves which exhibit a maximum intensity have been fitted using a hard sphere model and a preliminary coarse description for the fractal particles which seems to show that the correlations are due to purely excluded-volume effects.

Growth and Structure of Alumino-Silicate Polymers

ABSTRACTGels have been prepared in the H2O, HOiPr, (BuO)2Al-O-Si(OEt)3 ternary phase diagram in a large range of oxide concentrations. The gelation time is governed by the initial water concentration, showing that the hydrolysis of Si-OR groups is the rate-determining process for the gelation.The structure of clusters and the kinetics of aggregation have been studied by SANS. We observe mass-fractal particles characterized by a fractal dimension of 1.9, in agreement with the existence of a cluster-cluster aggregation mechanism during the gelation. The scattering curves exhibit a maximum intensity corresponding to interparticle correlations due to purely excluded-volume effects.

NMR study of the sol/gel polymerization

Kinetics and mechanisms of the hydrolysis-condensation reactions, starting with tetraethyl orthosilicate (TEOS), have been studied by 29 Si NMR. A standard experimental procedure for the sol/gel process was used: acid-catalyzed reactions and different concentration ratios of alkoxide and water. The inorganic polymerization was influenced by the following experimenta) parameters: — The starting alkoxides which may exhibit weakly reactive “Si-OR groups”. — The use of gel precursors with different chain lengths which lead to parasite ester exchange reactions. — The variations of pH which modify hydrolysis and condensation rates. — The H 2 O content where an excess of water was required to fully separate hydrolysis and condensation domains, and to eliminate “OR groups” in the gel.

A high-resolution solid-state 29 Si n.m.r. study of ZSM—5 type zeolites

29Si solid-state n.m.r. spectra of ZSM—5 indicate that the nature of the observed spectrum depends on the presence of ≡SiOR (R = H +, Na + or TPA +) groups inside the zeolite lattice.

Alkylation of silica surfaces

Infrared spectroscopy and carbon content analyses have been used to study some solution phase methods for alkylating silica surfaces leading to the formation of surface SiOR, SiOSi(CH 3) 3, and SiR groups. Total silanol conversion under mild reaction conditions could be achieved using most of the SiMe 3 containing agents, there was little, if any, reaction with surface siloxane sites, and the modified surface was resistant to hydrolysis. With one exception, only partial conversion into SiOR was achieved (R = Me, Et, or i-Bu) and for R = Me, the analytical data indicated that extensive conversion of siloxane sites into SiOMe also occurred. Experiments with Grignard and alkyllithium reagents lead in some cases to complete conversion into  SiR (R = Me, Et, or n-Bu) but the modified surface was susceptible to hydrolysis.