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A two‐step sequence for the enantio‐ and diastereoselective synthesis of exclusively alkyl‐substituted acyclic allylic systems with a stereocenter in the allylic position is reported. The asymmetric induction and the site selectivity are controlled in an enantio‐ and regioconvergent nickel‐catalyzed C(sp3)−C(sp3) cross‐coupling of regioisomeric mixtures of racemic α‐/γ‐silylated allylic halides and primary alkylzinc reagents. The silyl group steers the allylic displacement towards the formation of the vinylsilane regioisomer, and the resulting C(sp2)−Si bond serves as a linchpin for the installation of various C(sp3) substituents in a subsequent step., A nickel‐catalyzed cross‐coupling of regioisomeric mixtures of racemic silylated allylic halides and primary alkylzinc reagents enables the enantio‐ and regioconvergent synthesis of vinylsilanes with an allylic stereocenter. The silyl group controls the regiochemical outcome and is at the same time a placeholder for another alkyl substituent that can be installed in a subsequent cross‐coupling.

International audience; Commercially available Ni(II) and Co(II) complexes – M(acac)2 (acac = acetylacetonate) and M(tmhd)2 (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedionato) – exhibit catalytic activity for alkene/vinylsilane dehydrogenative silylation (DS) and hydrosilylation (HS) with tertiary silanes without the use of any external reducing agents. Using the model compounds divinyltetramethylsiloxane a.k.a dvtms and vinylpentamethyldisiloxane a.k.a vpmds, different selectivities (HS, DS, undesired non-C–Si bond-forming reactions…) are observed whether nickel or cobalt catalysts are employed, with Ni being DS-selective and Co yielding bothHS and DS products. All four complexes are efficient at thermally inducing silicone-oil crosslinking under a non-inert atmosphere, and promote metal-dependent selectivity that is slightly different from model reactions, which HR-MAS NMR spectroscopy unveils. Additional observations as well as NMR studies of [Ni(tmhd)2 + reagent] mixtures provide some insights into the possible activation pathways.

Sila-molecules have recently attracted attention due to their promising applications in medical and industrial fields. Compared with all-carbon parent compounds, the different covalent radius and electronegativity of silicon from carbon generally endow the corresponding sila-analogs with unique biological activity and physicochemical properties. Vinylsilanes feature both silyl-hyperconjugation effect and versatile reactivities, developing vinylsilane-based Smiles rearrangement will therefore provide an efficient platform to assemble complex silacycles. Here we report a practical Ir(III)-catalyzed cycloaromatization of ortho-alkynylaryl vinylsilanes with arylsulfonyl azides for delivering naphthyl-fused benzosiloles under visible-light photoredox conditions. The combination of experiments and density functional theory (DFT) energy profiles reveals the reaction mechanism involving α-silyl radical Smiles rearrangement., Arene-fused siloles have attracted interest due to their promising applications in electronic and optoelectronic devices. Here, the authors report Ir(III)-catalyzed cycloaromatization of ortho-alkynylaryl vinylsilanes with arylsulfonyl azides via α-silyl radical Smiles rearrangement for accessing naphthyl-fused benzosiloles under visible-light photoredox conditions.

Here, we describe simple B(C6F5)3-catalyzed mono- and dihydrosilylation reactions of terminal alkynes by using a silane-tuned chemoselectivity strategy, affording vinylsilanes and unsymmetrical geminal bis(silanes). This strategy is applicable to the dihydrosilylation of both aliphatic and aryl terminal alkynes with different silane combinations. Gram-scale synthesis and conducting the reaction without the exclusion of air and moisture demonstrate the practicality of this methodology. The synthetic utility of the resulting products was further highlighted by the structural diversification of geminal bis(silanes) through transforming the secondary silane into other silyl groups. Comprehensive theoretical calculations combined with kinetical isotope labeling studies have shown that a prominent kinetic differentiation between the hydrosilylation of alkynes and vinylsilane is responsible for the chemoselective construction of unsymmetrical 1,1-bis(silanes)., A B(C6F5)3/silane-based system enables the chemoselective dihydrosilylation of terminal alkynes. Using a combination of different types of hydrosilanes, a series of unsymmetrical or symmetrical 1,1-bis(silanes) could be constructed.

The selective, intermolecular, homodimerization and cross-cycloaddition of vinylsilanes with unbiased 1,3-dienes, catalyzed by a pyridine-2,6-diimine (PDI) iron complex is described. In the absence of a diene coupling partner, vinylsilane hydroalkenylation products were obtained chemoselectively with unusual head-to-head regioselectivity (up to >98% purity, 98:2 E/Z). In the presence of a 4- or 2-substituted diene coupling partner, under otherwise identical reaction conditions, formation of value-added [2+2]- and [4+2]-cycloadducts, respectively, was observed. The chemoselectivity profile was distinct from that observed for analogous α-olefin dimerization and cross-reactions with 1,3-dienes. Mechanistic studies conducted with well-defined, single-component precatalysts ((Me)PDI)Fe(L(2)) (where (Me)PDI = 2,6-(2,6-Me(2)-C(6)H(3)N═CMe)(2)C(5)H(3)N; L(2) = butadiene or 2(N(2))) provided insights into the kinetic and thermodynamic factors contributing to the substrate-controlled regioselectivity for both the homodimerization and cross cycloadditions. Diamagnetic iron diene and paramagnetic iron olefin complexes were identified as catalyst resting states, were characterized by in situ NMR and Mössbauer spectroscopic studies, and were corroborated with DFT calculations. Stoichiometric reactions and computational models provided evidence for a common mechanistic regime where competing steric and orbital-symmetry requirements dictate the regioselectivity of oxidative cyclization. Although distinct chemoselectivity profiles were observed in cross-cycloadditions with the vinylsilane congeners of α-olefins, these products arose from metallacycles with the same connectivity. The silyl substituents ultimately governed the relative rates of β-H elimination and C–C reductive elimination to dictate final product formation.

A set of iridium(I) complexes of formula IrCl(κC,η2-IRCouR′)(cod) or IrCl(κC, η2-BzIRCouR′)(cod) (cod = 1,5-cyclooctadiene; Cou = coumarin; I = imidazolin-2-carbene; BzI = benzimidazolin-2-carbene) have beeen prepared from the corresponding azolium salt and [Ir(μ-OMe)(cod)]2 in THF at room temperature. The crystalline structures of 4b and 5b show a distorted trigonal bipyramidal configuration in the solid state with a coordinated coumarin moiety. In contrast, an equilibrium between this pentacoordinated structure and the related square planar isomer is observed in solution as a consequence of the hemilability of the pyrone ring. Characterization of both species by NMR was achieved at the low and high temperature limits, respectively. In addition, the thermodynamic parameters of the equilibrium, ΔHR and ΔSR, were obtained by VT 1H NMR spectroscopy and fall in the range 22–33 kJ mol−1 and 72–113 J mol−1 K−1, respectively. Carbonylation of IrCl(κC,η2-BzITolCou7,8-Me2)(cod) resulted in the formation of a bis-CO derivative showing no hemilabile behaviour. The newly synthesised complexes efficiently catalyze the hydrosilylation of alkynes at room temperature with a preference for the β-(Z) vinylsilane isomer.

Time-resolved investigation of deuterium-substituted silylene (SiD2) generated by laser flash photolysis of deuterium-substituted phenylsilane (PhSiD3) was carried out to obtain rate constants for its bimolecular reaction with ethylene (C2H4). The reaction was studied in the gas phase over the pressure range of 1–100 Torr (in SF6 bath gas) at 295 K. The rate constants for SiD2 + C2H4 were found to be independent of pressure and close in magnitude to the rate constants for the reaction of SiH2 + C2H4 at the high-pressure limit. They are consistent with a rapid isotopic scrambling mechanism similar to that of SiH2 + C2D4. While silirane, the main product produced from this reaction, was too labile to be detected, vinylsilane, another possible product, was ruled out by gas chromatography analysis. This reaction shows similarities to those of SiH2 + H2 and its isotopic counterparts.

The reactions of sulfonamidation of 1,1,3,3-tetramethyl-1,3-divinyldisiloxane, (allyloxy)trimethylsilane, trimethoxy(vinyl)silane and tris(2-methoxyethoxy)vinylsilane with trifluoromethanesulfonamide, arenesulfonamides and methanesulfonamide in the presence of (t-BuOCl + NaI) or N-bromosuccinimide proceed in a different manner depending on the substrate, reagent, and oxidant. The formation of the products of halosulfonamidation, heterocyclization, halogenation, solvent interception and desilylation is observed.

Oxygen and nitrogen heterocyclic systems are present in a large number of natural and synthetic compounds. In particular, oxa- and aza-silacyclane, tetrahydrofuran, benzofuran, cycloheptadifuranone, cycloheptadipyrrolone, pyrrolidine, lactone, lactam, phthalan, isochromanone, tetrahydroisoquinolinone, benzoindolizidinone, indoline and indolizidine scaffolds are present in many classes of biologically active molecules. Most of these contain a C=O moiety which can be easily introduced using carbonylative reaction conditions. In this field, intramolecular silylformylation and silylcarbocyclization reactions may afford heterocyclic compounds containing a carbonyl functional group together with a vinylsilane moiety which can be further transformed. Considering these two aspects, in this review a detailed analysis of the literature data regarding the application of silylformylation and silylcarbocyclization reactions to the synthesis of several heterocyclic derivatives is reported.

The zwitterionic compound [Cp*RhCl{(MeIm)2CHCOO}] is an efficient catalyst for the hydrosilylation of terminal alkynes with excellent regio- and stereoselectivity toward the less thermodynamically stable β-(Z)-vinylsilane isomer under mild reaction conditions. A broad range of linear 1-alkynes, cycloalkyl acetylenes, and aromatic alkynes undergo the hydrosilylation with HSiMe2Ph to afford the corresponding β-(Z)-vinylsilanes in quantitative yields in short reaction times. The reaction of aliphatic alkynes with HSiEt3 is slower, resulting in a slight decrease of selectivity toward the β-(Z)-vinylsilane product, which is still greater than 90%. However, a significant selectivity decrease is observed in the hydrosilylation of aromatic alkynes because of the β-(Z) → β-(E) vinylsilane isomerization. Moreover, the hydrosilylation of bulky alkynes, such as t-Bu–C≡CH or Et3SiC≡CH, is unselective. Experimental evidence suggests that the carboxylate function plays a key role in the reaction mechanism, which has been validated by means of density functional theory calculations, as well as by mass spectrometry and labeling studies. On the basis of previous results, we propose an ionic outer-sphere mechanism pathway in which the carboxylate fragment acts as a silyl carrier. Namely, the hydrosilylation mechanism entails the heterolytic activation of the hydrosilane assisted by the carboxylate function to give the hydrido intermediate [Cp*RhH{(MeIm)2CHCOO–SiR3}]+. The transference of the silylium moiety from the carboxylate to the alkyne results in the formation of a flat β-silyl carbocation intermediate that undergoes a hydride transfer from the Rh(III) center to generate the vinylsilane product. The outstanding β-(Z) selectivity results from the minimization of the steric interaction between the silyl moiety and the ligand system in the hydride transfer transition state., The authors express their appreciation for the financial support from the Spanish Ministry of Economy and Competitiveness MINECO/FEDER under the project CTQ2016-75884-P and the Regional Governments of Aragón/FEDER 2014–2020 “Building Europe from Aragón” (group E42_17R). In addition, the resources from the supercomputer “Memento,” technical expertise, and assistance provided by BIFIZCAM (Universidad de Zaragoza) are acknowledged.

A convenient strategy for synthesis of the various derivatives of 1,4-dihydropyridine (1,4-DHP), as one of the most important pharmaceutical compounds, is presented in this study. For this purpose, firstly, magnetic iron oxide nanoparticles (Fe3O4 NPs) were fabricated and suitably coated by silica network (SiO2) and trimethoxy vinylsilane (TMVS). Then, their surfaces were well functionalized with pyrimidine-2,4-diamine (PDA) as the main active sites for catalyzing the synthesis reactions. In this regard, the performance of three different methods including reflux, microwave (MW) and ultrasound wave (USW) irradiations have been comparatively monitored via studying various analyses on the fabricated nanocatalyst (Fe3O4/SiO2-PDA). Concisely, high efficiency of the USW irradiation (in an ultrasound cleaning bath with a frequency of 50 kHz and power of 250 W/L) has been well proven through the investigation of the main factors such as excellent surface-functionalization, core/shell structure conservation, particle uniformity, close size distribution of the particles, and great inhibition of the particle aggregation. Then, the effectiveness of the USW irradiation as a promising co-catalyst agent has been clearly demonstrated in the 1,4-DHP synthesis reactions. It has been concluded that the USW could provide more appropriate conditions for activation of the catalytic sites of Fe3O4/SiO2-PDA NPs. However, high reaction yields (89%) have been obtained in the short reaction times (10 min) due to the substantial synergistic effect between the presented nanocatalyst and USW.

The formation of a family of silicon- and siloxane-bridged multiferrocenyl derivatives carrying different functional groups attached to silicon, including Fc2(CH3)3C(CH2)2SiCH[double bond, length as m-dash]CH2 (5), Fc2(CH2[double bond, length as m-dash]CH-O)SiCH[double bond, length as m-dash]CH2 (6), Fc2(OH)SiCH[double bond, length as m-dash]CH2 (7), Fc2(CH2[double bond, length as m-dash]CH-O)Si-O-Si(O-CH[double bond, length as m-dash]CH2)Fc2 (8) and Fc2(CH2[double bond, length as m-dash]CH-O)Si-O-SiFc3 (9) is described. Silyl vinyl ether molecules 6, 8 and 9 and the heteroleptic vinylsilane 5 resulted from the competing metathesis reaction of lithioferrocene (FcLi), CH2[double bond, length as m-dash]CH-OLi or (CH3)3C(CH2)2Li with the corresponding multifunctional chlorosilane, Cl3SiCH[double bond, length as m-dash]CH2 or Cl3Si-O-SiCl3. The last two organolithium species have been likely formed in situ by fragmentation of the tetrahydrofuran solvent. Diferrocenylvinyloxyvinylsilane 6 is noteworthy since it represents a rare example of a redox-active silyl mononomer in which two different C[double bond, length as m-dash]C polymerisable groups are directly connected to silicon. The molecular structures of the silicon-containing multiferrocenyl species 5, 6, 8 and 9 have been investigated by single-crystal X-ray diffraction studies, demonstrating the capture and storage processes of two ring fragments resulting from the cleavage of cyclic THF in redox-active and stable crystalline organometallic compounds. From electrochemical studies we found that by changing the anion of the supporting electrolyte from [PF6]- to [B(C6F5)4]-, the redox behaviour of tetrametallic disiloxane 8 can be switched from a poorly resolved multistep redox process to four consecutive well-separated one-electron oxidations, corresponding to the sequential oxidation of the four ferrocenyl moieties.

We report here that a cobalt catalyst generated from a cobalt(II) salt and a ligand using magnesium metal is capable of promoting hydroarylation reactions through chelation-assisted C−H activation. With the appropriate choice of the ligand and other reaction conditions, ketimine- or aldimine-directed branched selective hydroarylations of styrenes and ketimine-directed hydroarylations of vinylsilane have been achieved. The reported catalytic systems may serve as more convenient alternatives to previously developed catalytic systems employing Grignard reagents as reducing agents. MOE (Min. of Education, S’pore) Accepted version

Vinylsilanes are versatile and efficient nucleophiles in cross-coupling reactions. Herein is described the use of tetrabutylammonium bifluoride as a mild, cheap and scalable activating agent in several copper-catalyzed vinylsilane cross-couplings.

Cooperative catalysis enables the direct enantioselective α-allylation of linear prochiral esters using Si-substituted allyl electrophiles. The Si-substituent directs the regioselectivity of enantioselective bond formation and provides products containing synthetically versatile pentafluorophenyl ester and vinylsilane moieties. Critical to the efficacy of this process was the recognition that the ancillary ligand on palladium could be altered to prevent formation of a deleterious ether by-product, whilst retaining enantioselectivity through the Lewis base catalyst. Flexibility such as this is unique to cooperative catalysis events and provides efficient access to an array of enantioenriched products that are orthogonally functionalized and easily modified.

New biodegradable network polymers containing siloxane-linked polymeric prodrugs of 5-ammino-2-hydroxybenzoic acid (5-ASA) in the main chain were prepared by ter polymerization of methacrylic acid (MA), 2-hydroxyethylmethacrylate (HEMA), and bis (trimethylsilyloxy) methylsilane (VBM) in the presence of some new cross-linking agents.The monomers and polymers were characterized by FT-IR and 1H-NMR spectroscopy, and their thermal stability studied by DSC analysis. The hydrolysis of them were carried out in cellophane membrane dialysis bags containing aqueous buffer solution at 37 C. Detection of the hydrolysis product by UV spectroscopy method showed that attaching of siloxane units in these hydrogels modified this drug delivery system.

The control of morphology and interface in poly(styrene-ethylene/butylene-styrene) (SEBS) composites with graphitic fillers is extremely important for the design of piezoresistive sensors for body motion or flexible temperature sensors. The effects of a high amount of graphite (G) and silane coupling agent on the morphology and properties of SEBS composites with anisotropic mechanical properties are reported. The physical and chemical bonding of silane to both G and SEBS surface was proved by EDX and TGA results; this improved interface influenced both the thermal and mechanical properties of the composite. The vinyltriethoxysilane (VS) promoted the formation of char residue and, being tightly bound to both SEBS and G, did not show separate decomposition peak in the TGA curve of composites. The mechanical properties were measured on two perpendicular directions and were improved by both the addition of VS and the increased amount of G; however, the increase of storage modulus due to orientation (from 5 to 15 times depending on the composition and direction of the test) was more important than that provided by the increase of G concentration, which was a maximum of four times that obtained for 15 wt % graphite. A mechanism to explain the influence of G content and treatment on the variation of storage modulus and tan δ depending on the direction of the test was also proposed.

Pt nanoparticles with controlled sizes between 1.6–7.0 nm were anchored onto the surface and pores of SBA-15 silica support. The catalysts were characterized by TEM-ED, BET, XRD, and ICP-MS techniques and were tested in liquid phase hydrosilylation of phenylacetylene with triethylsilane. The activity of the 7.0 nm Pt nanoparticles anchored onto the surface of SBA-15 in hydrosilylation (TOF = 0.107 molecules·site−1·s−1) was ~2 times higher compared to the 5.0 nm Pt/SBA-15 (TOF = 0.049 molecules·site−1·s−1) catalyst and ~10 times higher compared to the 1.6 nm Pt/SBA-15 (TOF = 0.017 molecules·site−1·s−1) catalyst. Regarding the selectivity, bigger nanoparticles produced more vinylsilane-type products (α- and β-(E)-products) and less side products (mainly ditriethylsilane, triethyl(1-phenylethyl)silane and triethyl(phenethyl)silane derived likely from the reduction of the vinylsilane products). However, the selectivity towards the β-(E)-triethyl(styryl)silane was higher in the case of 1.6 nm Pt/SBA-15 catalyst compared to 5.0 nm Pt/SBA-15 and 7.0 nm Pt/SBA-15, respectively, which can be attributed to the beneficial effect of the size differences of the Pt nanoparticles as well as the differences of the quality and quantity of Pt/SiO2 interfaces.

Transition metal catalysis has emerged as a powerful strategy to expand synthetic flexibility of protein modification. Herein, we report a cationic Ru(II) system that enables the first example of alkyne hydrosilylation between dimethylarylsilanes and $\textit{O}$-propargyl-functionalized proteins using a substoichiometric amount or low-loading of Ru(II) catalyst to achieve the first C–Si bond formation on full-length substrates. The reaction proceeds under physiological conditions at a rate comparable to other widely used bioorthogonal reactions. Moreover, the resultant $\textit{gem}$-disubstituted vinylsilane linkage can be further elaborated through thiol–ene coupling or fluoride-induced protodesilylation, demonstrating its utility in further rounds of targeted modifications.

The mechanisms and origins for the Pd- and Ni-catalyzed regioselective hydrosilylation of allene have been investigated by means of density functional theory (DFT) calculations. The free-energy profiles of Pd- and Ni-catalyzed reactions with small and bulky N-heterocyclic carbene (NHC) ligands are calculated to determine the mechanism for regioselectivities. The calculation results show that different metals (Ni vs Pd) lead to regiochemical reversals for the hydrosilylation of allene. The allylsilane is the major product via palladium catalysis with small NHC ligand, while the vinylsilane is the major product via nickel catalysis with bulky NHC ligand. Both electronic and steric factors play a key role in the regioselectivities for the hydrosilylation of allene via Pd and Ni catalysts. The calculation results are in good agreement with observed regioselectivities and could provide insights into the design of new catalysts for the regioselectivity of hydrosilylation reactions.

Silane crosslinked polyethylene cable insulation occasionally fails to meet the aging requirements given in technical standards. The purpose of this paper is to investigate this phenomena and establish whether the safety margin of aging tests can be increased by changes in manufacture or test procedures. Using a number of cable types with different compositions and dimensions, the evolution of the absolute values of tensile strength and elongation at break upon aging was obtained. The results show that the major changes in mechanical properties happen within the first 24-48 h. This finding is valid both for ethylene vinylsilane copolymers and for grafted silane systems. In general, the effect is more pronounced for the 100°C compatibility test. Statistical analysis shows that insulation crosslinked in a hot waterbath will exhibit this behavior to a lesser extent, thus increasing the safety margin in aging tests, compared with ambient curing. This paper demonstrates that preconditioning at 70°C has no significant impact on aging properties. In addition, only small variations in mechanical properties were seen when changing the process parameters. It is concluded that further crosslinking is the principal cause of the phenomena under investigation.

The formation of negative ions following low energy (0–12 eV) electron attachment to the title compounds is studied in a crossed electron-molecular beam experiment applying mass spectrometric detection of the anions. All silane derivatives presently studied are weak electron scavengers which also holds for trichlorovinylsilane. The behaviour in the silanes is hence in strong contrast to the hydrocarbons where chlorination usually results in a strong increase of the cross section for dissociative electron attachment (DEA) yielding intense Cl− signals already at very low electron energies (near 0 eV). The different behaviour can be explained by the appreciably stronger Si–Cl binding energy compared to that of C–Cl making the DEA reaction leading to Cl− endothermic for trichlorovinylsilane while the corresponding reaction is exothermic for most chlorinated hydrocarbons. Trichlorovinylsilane and tetravinylsilane undergo various further DEA reactions via different resonances at higher energy (in the range between 4 and 10 eV) leading to a variety of ionic fragments. These reactions range from simple bond cleavages to considerably more complex unimolecular decompositions involving multiple bond cleavages, hydrogen transfer in the temporary negative ion and formation of new bonds. Trimethylvinylsilane yields only one single fragment due to the loss of a neutral hydrogen atom ((M−H)−).

In order to prevent corrosion of aluminium pigment in water, coated flaky aluminium powder was prepared through the sol–gel process, in which tetraethoxysilane (TEOS) and tris(2-methoxyethoxy)vinylsilane (VTMOEO) were adopted as precursors. The influences of the dosage of precursors, ethylenediamine, water and ethanol, as well as the reaction temperature and reaction time on the corrosion inhibition efficiency were investigated. Under the optimum conditions, the corrosion inhibition efficiency reached 99.2% in alkaline media of pH 11. The analysis with SEM, FTIR, EDS and XPS showed that sol–gel coatings had successfully encapsulated on the surface of clear flaky aluminium powders.

A catalytic method for enantioselective conjugate addition (ECA) of Si-containing vinylaluminum reagents to β-substituted cyclopentenones and cyclohexenones is described. Reactions are promoted by 1.0–5.0 mol % of a bidentate NHC–Cu complex, which is prepared from air stable CuCl2•2H2O and used in situ, and typically proceed to completion within 15–20 minutes. The requisite vinylmetals are generated efficiently by a site-selective hydroalumination of an alkyne with dibal–H. The desired products, containing a quaternary carbon stereogenic center, are obtained in 48–95% yield after purification and in 89:11 to >98:2 enantiomer ratio (er). The vinylsilane moiety within the products can be functionalized to afford acyl, vinyliodide or desilylated alkenes in 67% to >98% yield and with >90% retention of the alkene's stereochemical identity. The utility of the catalytic process is illustrated in the context of a concise enantioselective synthesis of riccardiphenol B.

Compósitos de PP com fibras curtas de coco foram preparados em extrusora, com dois perfis de temperatura, visando avaliar o efeito compatibilizante de PP modificado com vinilalcoxisilano e com anidrido maleico. Foi verificado que os dois agentes de acoplamento melhoraram o módulo elástico, a tensão máxima e a resistência à absorção de água quando os materiais foram processados utilizando‑se um perfil de temperaturas mais elevadas. A morfologia dos compósitos também ficou mais homogênea na presença dos agentes de acoplamento, especialmente naqueles processados na temperatura mais alta. Esses resultados indicam que a temperatura é uma variável fundamental no estabelecimento das interações envolvendo os processos de compatibilização. PP composites filled with coir short fibers were prepared in an extruder using two temperature profiles. The objective was to evaluate the compatibilizing effect of PP modified with vinylsilane and with maleic anhydride. Both coupling agents improved elastic modulus, tensile strength and water absorption resistance when the materials were processed at the highest temperature profile. The composite morphology was more homogeneous in the presence of the coupling agents, mainly in the composites processed at the highest temperatures. These results indicate that temperature is a key variable for the establishment of the interactions involved in the coupling processes.

Thin films were deposited from vinyltriethoxysilane (VTES) and tetravinylsilane (TVS) by radio frequency (RF) cold plasma operated in a pulsed mode on the surface of E-glass fibers. Film thickness and molecular structure was controlled by the length of plasma cycle expressed as ratio of time on/time off (ton/toff). It was found that ton as short as 1 ms was long enough for vinylsilane precursor gas fragmentation. Time toff was the main parameter controlling structural variables of the deposited films. Short toff led to apparently disordered and cross-linked structure. Increased toff led to more uniform films with enhanced properties compared to the short toff deposited films. Only films prepared under long toff improved adhesion between the glass fiber and polyester resin as measured employing the micro-droplet test. Strong effect of the molecular structure of the vinylsilane precursor has also been observed under the conditions used. VTES film deposited under ton/toff = 1:999 increased interfacial adhesion only by 20%, TVS film deposited at 1:99 improved adhesion by 48%, compared to the solution deposited coating of the VTES used commercially.

This article summarises our recent efforts towards using β-halovinylsilanes in a new approach to oligoyne assembly. β-Halovinylsilanes are particularly useful masked alkynes since the free alkyne can be released under mild reaction conditions by treatment with fluoride. To this end, β-chlorovinylsilane and β-fluorovinylsilane motifs have been incorporated into a 1-trimethylsilyl-hexa-3-en-1,5-diyne scaffold. Oxidative dimerisation of this masked triyne provides a centrosymmetric masked hexayne, which serves as our building block for oligoyne assembly. We have assembled a masked dodecayne using this methodology and shown that treatment of the masked dodecayne with fluoride effects a four-fold dechlorosilylation to provide the corresponding dodecayne, which is the longest aryl end-capped oligoyne reported to date. This long-chain oligoyne proved to be highly unstable. Molecular encapsulation provides a potential solution to the problem of instability associated with long-chain oligoynes, and preliminary results where one of our masked hexaynes was modified in order to form an insulated system are presented.

A series of novel oligomers with promesogenic groups on both termini were prepared by a hydrosilylation reac- tion between well-defined telechelic oligocarbosilazanes end-fitted with vinylsilane (SiVi) groups and promesogenic com- pounds containing one reactive hydrosilane (SiH) group. We investigated the correlations between the structure of the resulting mesogen end-capped oligomers and their phase behavior as examined by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM).

Radical (co)polymerization behavior of alkoxyvinylsilanes [tri(isobutoxy)vinylsilane 1, triethoxyvinylsilane 2, di(isobutoxy)methylvinylsilane 3, di(isobutoxy)phenylvinylsilane 4, diethoxymethylvinylsilane 5, and diethoxyphenylvinylsilane 6] was systematically investigated. Homopolymerization and copolymerization with styrene of these alkoxyvinylsilanes were performed under various conditions in order to find appropriate initiating systems for the radical polymerizations. Transformation of some of the copolymers into poly[(vinyl alcohol)-co-styrene]s was examined via oxidative cleavage of the Si-C bonds in the alkoxyvinylsilane repeating units.

The preparation of various (hex-5-ynyl)silanes was achieved following two different synthetic approaches from readily available materials such as 4-bromobutene, 6-iodohexyne and chlorosilanes. Different reaction conditions for intramolecular hydrosilylation were tested to prepare the corresponding 2-methylidene-1-silacyclohexanes. Notably, the use of Speier’s catalyst allowed the regioselective formation of the desired products in moderate yields.

The reaction of α-chlorine-substituted allylsilanes with primary amines was promoted by CuCl to result in the selective formation of secondary amines bearing the vinylsilane functionality by a probable SN2′-allylation keeping the silyl group intact.

Fluoroalkanoyl peroxide [RF-C(=O)OO(O=)C-RF] decomposes homolytically through concerted three bond radical fission to afford fluoroalkyl radical (RF·) selectively, although the corresponding alkanoyl peroxide [R-C(=O)OO(O=)C-R] decomposes homolytically through stepwise radical fission to afford acyloxy radical [R-C(=O)O·] and alkyl radical [R·]. This decomposition of fluoroalkanoyl peroxide was applied to the direct fluoroalkylation of two end-sites of vinylsilane oligomers and (meth)acrylate oligomers. Fluoroalkyl end-capped trimethoxyvinylsilane oligomers [RF-(CH2CHSi(OMe)3)n-RF] thus obtained were applied to the surface modification on glass and traditional organic polymers such as PMMA and rubbers to exhibit not only strong hydrohobicity but good oleophobicity imparted by fluorine with extremely higher adhesive property on their surface. Fluoroalkyl end-capped actylate and methacrylate oligomers exhibited surface active properties imparted by fluorine, the same as for low-molecular weight fluorinated surfactants, and these fluorinated cooligomers formed the nanometer size-controlled self-assembled molecular aggregates in aqueous and organic media. These fluorinated molecular aggregates interacted with a variety of guest molecules such as low molecular biocides, fullerenes, and carbon nanotubes to afford the corresponding fluorinated oligomers/guest molecules nanocomposites. These fluorinated oligomers were applied to the preparation of fluorinated oligomers/silica gel nanocomposites and cross-linked fluorinated oligomeric nanoparticles.