SiH Groups Research Articles

Rational Design of Oil-Resistant and Electrically Conductive Fluorosilicone Rubber Foam Nanocomposites for Sensitive Detectability in Complex Solvent Environments.

Recent years have witnessed the explosive development of highly sensitive smart sensors based on conductive polymer foam materials. However, the design and development of multifunctional polymeric foam composites as smart sensors applied in complex solvent and oil environments remain a critical challenge. Herein, we design and synthesize vinyl-terminated polytrifluoropropylmethylsiloxane through anionic ring-opening polymerization to fabricate fluorosilicone rubber foam (FSiRF) materials with nanoscale wrinkled surfaces and reactive Si-H groups via a green and rapid chemical foaming strategy. Based on the strong adhesion between FSiRF materials and consecutive oxidized ketjen black (OKB) nano-network, multifunctional FSiRF nanocomposites were prepared by a dip-coating strategy followed by fluoroalkylsilane modification. The optimized F-OKB@FSiRF nanocomposites exhibit outstanding mechanical flexibility in wide-temperature range (100 cycle compressions from -20 to 200 °C), structure stability (no detached particles after being immersed into various aqueous solutions for up to 15 days), surface superhydrophobicity (water contact angle of 154° and sliding angle of ∼7°), and tunable electrical conductivity (from 10-5 to 10-2 S m-1). Additionally, benefiting from the combined actions of multiple lines of defense (low surface energy groups, physical barriers, and "shielding effect"), the F-OKB@FSiRF sensor presents excellent anti-swelling property and high sensitivity in monitoring both large-deformation and tiny vibrations generated by knocking the beaker, ultrasonic action, agitating, and sinking objects in weak-polar or nonpolar solvents. This work conceivably provides a chemical strategy for the fabrication of multifunctional polymeric foam nanocomposite materials as smart sensors for broad applications.

Durable and highly hydrophobic flax fabrics designing via “grafting to” method using catalysed hydrosilylation

Highly hydrophobic flax fabrics with durable properties were prepared via “grafting to” method for self-cleaning application. Flax fabrics were firstly functionalized with vinyl groups using 1,3-divinyltetramethyldisilazane (DVTS). Then, the vinyl functionalized flax fabrics were grafted by poly(hydromethylsiloxane-co-dimethylsiloxane) (PDMS-co-PHMS) via a hydrosilylation reaction using Karstedt catalyst, between Si-H groups present in PDMS-co-PHMS and vinyl groups present onto the vinyl functionalized flax fabrics. The prepared fabrics were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-rays fluorescence, confocal laser scanning microscopy (CLSM) and tensile test. The modified fabrics displayed highly hydrophobic properties with contact angle (θ) about 147° ± 5 and a sliding angle (SA) of about 15° ± 2, making them ideal for practical self-cleaning applications. Furthermore, good durability with excellent washing resistance was also obtained for these fabrics.

EXPERIMENTAL SYNTHESIS OF ZIRCONIA NANOPARTICLES USING VARIOUS CAUSTIC FUSION TEMPERATURES DERIVED FROM NATURAL MATERIAL ZIRCON SAND IN INDONESIA

The purpose of this research was to analyze the effect of caustic fusion temperature on the size, and impurity of Nano-zircon produced from zircon sand. Caustic fusion of zircon sand using NaOH was conducted with varied temperatures of 400-600 °C, followed by water leaching, acid leaching, precipitation, and calcination to produce zirconia nanoparticle powder. The synthesized zirconia nanoparticle was analyzed using FT-IR and SEM. The yield of the product was also determined and the correlation between varied caustic fusion temperature and yield and diameter product was determined using the least square equation. From the FT-IR spectrum, it is shown that the presence of -OH hydroxyl groups at a wavelength of 3417.725 cm-1 indicates the presence of ≡Si-OH groups. At wave 2258.504 cm-1 indicate the presence of a Si-H group in the form of ≡Si-O-OH groups. The correlation between the temperature of caustic fusion and yield follows the equation y = -0.00184x + 1.244 and R2 = 0.9888 indicating that the higher the temperature of caustic fusion the higher the yield of zirconia nanoparticle product. The optimum temperature was found at 450 °C with a yield of 0.42% and a size of 32.984 nm.

Cost-Effective Ultrabright Silicon Quantum Dots and Highly Efficient LEDs from Low-Carbon Hydrogen Silsesquioxane Polymers.

Cost-effective methods of synthesizing bright colloidal silicon quantum dots (SiQDs) for use as heavy-metal-free QDs, which have applications as light sources in biomedicine and displays, are required. We report simple protocols for synthesizing ultrabright colloidal SiQDs and fabricating SiQD LEDs based on hydrogen silsesquioxane (HSQ) polymer synthesis. Red photoluminescence with a quantum yield (PLQY) of 60-80% and LEDs with an external quantum efficiency (EQE) of >10% were obtained at 1/3600th of the cost of existing methods. This was achieved by using HSiCl3 and a low-polarity solvent to prepare the HSQ polymer and by optimizing the LED hole-injection layer thickness. A stochastic analysis of 31 SiQD syntheses revealed that SiQDs with the highest PLQYs were obtained from a hard, low-carbon HSQ polymer precursor containing many Si-H groups and cage structures. Notably, simple FTIR measurements predicted whether a HSQ polymer would yield high-PLQY SiQDs and high-EQE LEDs. These straightforward, cost-effective protocols should lead to advances in SiQD synthesis and LED fabrication methods.

White-Light initiated Mn2(CO)10/HFIP-Catalyzed anti-Markovnikov hydrosilylation of alkenes

This study presents a highly efficient and mild method for radical hydrosilylation of alkenes. The reaction proceeds under white-light, in the presence of Mn2(CO)10 pre-catalyst and HFIP as an additive, at r.t. and under air. Under white-light, [Mn]• is generated, which activates the Si–H-group to form Si• and trigger the autocatalytic process. HFIP acts as a unique activator which enables synthesis of the products with yields close to quantitative and with anti-Markovnikov selectivity. The method is applicable to terminal alkenes, including those with O-, N- and halogen-containing functional groups, styrene and allylbenzene derivatives, etc., as well as to a wide range of alkyl-, phenyl-, siloxy- and alkoxy-containing tertiary hydrosilanes. These conditions turned out to be most efficient for hydrosilylation of gaseous reagents such as ethylene and acetylene. In both cases the products showed quantitative yield at 1 atm and at r.t. The method is easily up-scalable in batch- and flow-modes.

Gestational intermittent hypoxia induces endothelial dysfunction and hypertension in pregnant rats: role of endothelin type B receptor†.

Obstructive sleep apnea is a recognized risk factor for gestational hypertension, yet the exact mechanism behind this association remains unclear. Here, we tested the hypothesis that intermittent hypoxia, a hallmark of obstructive sleep apnea, induces gestational hypertension through perturbed endothelin-1 signaling. Pregnant Sprague-Dawley rats were subjected to normoxia (control), mild intermittent hypoxia (10.5% O2), or severe intermittent hypoxia (6.5% O2) from gestational days 10-21. Blood pressure was monitored. Plasma was collected and mesenteric arteries were isolated for myograph and protein analyses. The mild and severe intermittent hypoxia groups demonstrated elevated blood pressure, reduced plasma nitrate/nitrite, and unchanged endothelin-1 levels compared to the control group. Western blot analysis revealed decreased expression of endothelin type B receptor and phosphorylated endothelial nitric oxide synthase, while the levels of endothelin type A receptor and total endothelial nitric oxide synthase remained unchanged following intermittent hypoxia exposure. The contractile responses to potassium chloride, phenylephrine, and endothelin-1 were unaffected in endothelium-denuded arteries from mild and severe intermittent hypoxia rats. However, mild and severe intermittent hypoxia rats exhibited impaired endothelium-dependent vasorelaxation responses to endothelin type B receptor agonist IRL-1620 and acetylcholine compared to controls. Endothelium denudation abolished IRL-1620-induced vasorelaxation, supporting the involvement of endothelium in endothelin type B receptor-mediated relaxation. Treatment with IRL-1620 during intermittent hypoxia exposure significantly attenuated intermittent hypoxia-induced hypertension in pregnant rats. This was associated with elevated circulating nitrate/nitrite levels, enhanced endothelin type B receptor expression, increased endothelial nitric oxide synthase activation, and improved vasodilation responses. Our data suggested that intermittent hypoxia exposure during gestation increases blood pressure in pregnant rats by suppressing endothelin type B receptor-mediated signaling, providing a molecular mechanism linking intermittent hypoxia and gestational hypertension.

Development of Cyclic Tetrasiloxane Polymer as a High-Performance Dielectric and Hydrophobic Layer for Electrowetting Displays.

Cyclic tetrasiloxane polymer (CTP) has recently garnered interest as a hydrophobic material with unique properties. This study aims to enhance the dielectric constant of CTP films by introducing excess Si-H groups and to explore the impact of synthesis and processing conditions on the resulting properties. The film demonstrates high hydrophobicity, with contact angles of 107° in air and 165° in n-decane, along with a notable dielectric constant of 5.1°. Furthermore, the CTP film displays reversible electrowetting behavior with low contact angle hysteresis (2°) and possesses good transparency (∼99%) and thermal stability. As such, the CTP film has significant potential as a material for the electric wetting of hydrophobic dielectric layers and may serve as a promising alternative in electrowetting applications.

Regioselective Derivatization of Silylated [20]Silafulleranes

Silafulleranes with endohedral Cl- ions are a unique, scarcely explored class of structurally well-defined silicon clusters and host-guest complexes. Herein, we report regioselective derivatization reactions on the siladodecahedrane [nBu4N][Cl@Si20(SiCl3)12Cl8] ([nBu4N][1]), which has its cluster surface decorated with 12 SiCl3 and 8 Cl substituents in perfect Th symmetry. The room-temperature reaction of [nBu4N][1] with excess iBu2AlH in ortho-difluorobenzene (oDFB) furnishes perhydrogenated [nBu4N][Cl@Si20(SiH3)12H8] ([nBu4N][2]) in 50% yield; the non-pyrophoric [2]- is the largest structurally authenticated (by X-ray diffraction) hydridosilane known to date. A simple switch from pure oDFB to an oDFB/Et2O solvent mixture suppresses core hydrogenation and results in the formation of [nBu4N][Cl@Si20(SiH3)12Cl8] ([nBu4N][3]). In addition to the exhaustive Cl/H exchange at all 44 Si-Cl bonds of [1]- and the regioselective 36-fold silyl group hydrogenation, we achieved the simultaneous introduction of Me substituents at all 8 SiCl vertices along with the conversion of all 12 SiCl3 to SiH3 groups by treating [nBu4N][1] with Me2AlH/Me3Al in oDFB ([nBu4N][Cl@Si20(SiH3)12Me8], [nBu4N][4]; 73%). Quantum-chemical free-energy calculations find an SN2-Si-type hydrogenation of the exohedral SiCl3 moieties in [1]- (trigonal-bipyramidal intermediate) slightly preferred over metathesis-like SNi-Si substitutions (four-membered transition state). Cage hydrogenation likely occurs via SNi-Si processes. The experimentally demonstrated influence of an Et2O co-solvent, which drastically increases the respective reaction barriers, is attributed to the increased stability of the resulting iBu2AlH-OEt2 adduct and its higher steric bulk compared to free iBu2AlH.

A Study of the Ceramicisation of Allylhydridopolycarbosilane by Thermal Volatilisation Analysis and Solid-State Nuclear Magnetic Resonance

AHPCS is a pre-ceramic polymer utilised as a precursor to SiC. An initial polymerisation to a cross-linked network is followed by a complex sequence of processes ultimately leading to amorphous SiC. Using thermal volatilisation analysis (TVA) accompanied with solid-state NMR (SSNMR), FTIR, MS, DSC and TGA the complete thermal profile was identified. Between 160 – 300 °C, AHPCS cross-links through the allyl group and undergoes some carbon-silicon rearrangement, with a volatilisation of low mass oligomeric material and significant volumes of hydrogen released from dehydrocoupling of SiH moieties. By 300 °C the allyl group is completely cross-linked but the polymer starts to undergo pyrolytic degradation of the network, with the release of chain fragments and low molar mass species such as methane, ethane, methanol, propane, propene and silane species. Hydrogen once again becomes the major volatile product above 400 °C due to higher proportion of dehydrocoupling forming Si–C and Si–Si bonds. Small chain fragments are seen in the form of larger alkyl silanes. These fragments come from the chain scission of the polymer at weaker parts of the network. The process of side group scission leads to further radical recombination reactions of silicon and carbon atoms to build the SiC network. By 500 °C higher proportion of dehydrocoupling occurs with recombination of Si–Si and Si–C species. The Si–H bonds in -SiH3 groups have completely cleaved along with C-H bonds in the CH3 and CH2 groups leaving SiC, -SiH and HCSi3 present in the material. This bond cleavage leads the silicon and carbon radical species to undergo radical recombination in the network with the volatile release being dominated by H2. By 650 °C the cleavage and recombination of remaining -SiH2-, -SiH- and HCSi3 groups ultimately form amorphous SiC. The volatiles released are mostly hydrogen with very few condensable products seen. Finally, SiC is then crystallised at higher temperatures forming β-SiC at 1100 °C and then subsequently α-SiC above 1500 °C.

Research on the Fluorescence Properties of Protoporphyrin-Modified Amphiphilic Polysilane

Polysilanes are polymers with unique luminescent properties, which will be enhanced by functional side group modifications. In this paper, amphiphilic functional polysilane is synthesized by Si-H addition reaction between Si-H and alkene bonds. Polymethylsilane is selected as matrix which is full of reactive Si-H groups and azobisisobutyronitrile is used as the initiator. The product shows good luminescence (emission band between 400-650 nm), good solubility (soluble in various solvents such as toluene, tetrahydrofuran, n-hexane, dimethyl sulfoxide, alcohol and water) and environmental friendliness, which can be applied to flexible luminescent devices and solvent-based fluorescence detection in the future.

Effects of N2 and O2 plasma treatments of quartz surfaces exposed to H2 plasmas

This paper presents a study of methods for reducing the erosion of SiO2 in a high-power density (10–40 W/cm3), purely inductive H2/Ar plasma, using a toroidal transformer-coupled plasma source operated at 0.5 Torr. Quartz samples were exposed to plasma densities of 1–3 × 1013 cm−3 and H atom temperatures of 4000–8000 K [electron densities and H translational temperatures were measured by Stark and Doppler broadening of H Balmer-β (Hβ) emission at 486.1 nm]. Laser interferometry was employed to monitor time-resolved temperatures of the quartz substrate. Etching rates were measured by stylus profilometry, and roughness was quantified by atomic force microscopy (AFM). For 5 min discontinuous H2/Ar plasma exposure (0.5 Torr, 16 W/cm3, 1 min plasma-on, 9 min plasma-off per cycle with five cycles), the etching rate during the plasma-on time was 224 nm/min. This was much higher than the 16 nm/min rate observed for a continuous 1 h H2/Ar plasma exposure. This trend was ascribed to the higher substrate temperatures reached with continuous plasma operation and a negative dependence of the etching rate on temperature, described by an activation energy of roughly −5 kcal/mol. When exposure to 1 min H2/Ar plasmas was alternated with 1 min O2/Ar plasma treatments and 12 min plasma-off periods, the etching rate was reduced to near-zero and the extent of surface roughness was reduced by at least fivefold. N2/Ar plasma treatments were less effective in reducing the etching rate (to 57 nm/min), while the roughness to the surface caused by exposure to the H2/Ar 1 min plasmas was nearly eliminated. A mechanism for the erosion process is proposed, involving the penetration of H atoms below the surface where they insert into Si–O–Si linkages to form SiH and SiOH groups. This opening of the SiO2 network allows easier penetration of H, further bond breakage, and crack propagation that eventually leads to the shedding of small silica particles. Periodic exposure to O atoms hydroxalizes these subsurface regions and subsequently reforms Si–O–Si linkages, accompanied by the formation of H2O that presumably diffuses to the surface and desorbs.

Sex Differences in Orofacial Sensitivity, Visceral Sensitivity, and Brain Activity in an Animal Model of Stress-induced Pain Hypersensitivity

Temporomandibular disorder (TMD) and irritable bowel syndrome (IBS) are two chronic overlapping pain conditions that present with significant comorbidity. Both conditions are more prevalent in women and are exacerbated by stress. While peripheral mechanisms might contribute to pain hypersensitivity for each individual condition, mechanisms underlying the comorbidity are poorly understood, complicating pain management when multiple conditions are involved. We hypothesize that changes in brain function initiated by pre-existing pain combined with stress contributes to development of de novo pain in susceptible individuals. Using an animal model (masseter muscle inflammation followed by stress) that induces de novo Comorbid visceral Pain Hypersensitivity (CPH) in rats, we reported more robust and longer duration CPH in female rats compared to males. The effects of stress alone (Stress-Induced Hypersensitivity, SIH) were examined. The relative percentage of male (9/12) and females (8/14) rats susceptible to stress (increased visceral pain one week post stress) was comparable. The stress resilient rats were excluded from further analysis of visceral pain. Preliminary data from both males and females showed SIH four weeks post stress, resolving by seven weeks in females (ANOVA, females p=.0250); data collection ongoing in males. Additional preliminary data show that stress alone increased orofacial mechanosensitivity in females (p=.0210, n=5), but not males (p=0.4, n=5). In the female cohort, the increased orofacial pain was only apparent in the susceptible females and not the resilient females. Analysis of functional connectivity using functional MRI is underway. Ultimately, changes in functional connectivity in SIH rats will be compared to CPH rats. This study supports our previous work using SIH and CPH groups, suggesting that hypersensitivity in males may resolve faster than in females. Grant support from NIDCR R01 DE029074.

Highly Branched Polycarbosilanes as Precursors For SiC Ceramics

The Grignard reaction of (chloroalkyl)chlorosilanes affords a series of highly branched polycarbosilanes featuring two types of terminal groups. The thermophysical properties of the resulting compounds are studied. The effect of the structure of the highly branched polymer and the nature of its terminal groups on the formation of a carbon residue (pyrolysate) is evaluated. The potential of application of poly(chloromethyl)-trichlorosilane with terminal SiH groups as a precursor for SiC ceramics is demonstrated.

Networks derived from poly(methylhydrosiloxane) of various average molecular weights – characterization and incorporation of Pt particles

In the work, polysiloxane networks were prepared by hydrosilylative cross-linking of two poly(methylhydrosiloxane)s (PMHS) differing in the average molecular weight: PMHS1 of Mn = 3 800 g/mol and PMHS2 of Mn = 13 800 g/mol using linear divinyldisiloxane (ViMMVi) and cyclic tetravinyltetrasiloxane (D4Vi) as cross-linkers. It was found that PMHS2-based materials were characterized by higher cross-link densities than the PMHS1-derived ones, the effect being more pronounced in the case of D4Vi than ViMMVi. This was explained by the presence of entangled chains in PMHS2 and high functionality of D4Vi. Higher cross-link density resulted in lower rate of platinum incorporation into PMHS2-based networks, conducted in PtCl4 solutions in tetrahydrofuran. The reaction of Pt4+ ions from the solutions with Si-H groups remaining in the networks led to the formation of metallic Pt nanoparticles (2–5 nm in size) in all the materials. Due to higher cross-link density, however, which inhibited Pt penetration into the bulk, surface metal coverage in the PMHS2-originated networks was higher as compared to the ones obtained from PMHS1. Presence of Pt resulted in most cases in the increase in residual mass after treatment at 1000 °C in Ar atmosphere (the so-called ceramic yield) with respect to the initial samples. Results of the studies point to the significant influence of the average molecular weight on properties of PMHS-based networks and may be helpful when planning the use of such materials as ceramic precursors or as carriers for metal particles for various, e.g. catalytic applications.

Hydrogen-Bridged Oligosilanylsilyl Mono- and Oligosilanylsilyl Dications.

Hydrogen‐bridged oligosilanylsilyl borates 8 [B(C6F5)4], 9[B(C6F5)4] and diborates 10 [B(C6F5)4]2 have been prepared by hydride transfer between α‐ω‐dihydrido‐ (11) and branched tetrahydrido‐oligosilanes (13) and trityl cation. The obtained cyclic intramolecularly stabilized silylium ions 8, 9 and bissilylium ion 10 were characterized by low temperature NMR spectroscopy supported by the results of density functional calculations. The branched Si−H−Si monocation 9 undergoes at low temperatures a fast degenerate rearrangement, which exchanges the Si−H groups with a barrier of 31 kJ mol−1 via an antarafacial transition state. Reaction of the branched monocation 9 with a second equivalent of trityl cation or of the branched oligosilane 13 with two equivalents of trityl cation, gives at −80 °C the corresponding bissilylium ion 10, an example for a new class of highly reactive poly‐Lewis acids.

In English

Fumed silica has found widespread application in industry due to variety of fascinating properties. Owing to its specific manufacturing process, it consists of finely dispersed particles and is featured with large specific surface area covered by profoundly reactive silanol groups which are available for chemical grafting. Spherical shape of fumed silica particles and lacking porosity provides a space-filling structure. These characteristics implement the fume silica’s utilization as high-surface-area carriers for various catalysts, i.e. metallic nanometer-sized particles, organic moieties, etc. Currently a great attention is called to on-surface grafting to improve the silica-based carrier. Most of research is carried out in area of liquid phase chemistry involving an abundance of expensive and often toxic solvents while the space-filling properties of silica are favoring reactions in fluidized bed conditions. In current research fumed silica (A-300) was a subject for hydridesilylation with triethoxysilane under fluidized bed conditions. In all synthesis reported in current research the insignificant amount of solvent (1.00 wt. % of the amount used in typical wet-chemical modifications method) was spent for the silica surface silylation. While the mass ratio of silica/TES was kept constant, other conditions, i.e. solvent/catalyst presence, surface pretreatment, additional treatment with water, and the fluidized bed heating mode have been varied. FTIR spectroscopy revealed the interaction between groups of triethoxysilane and silica surface silanol groups and demonstrated the effect of modification conditions on the density of the hydridesilyl groups coverage. The results of FTIR spectroscopic studies have confirmed the presence of grafted silicon hydride groups on the surface of modified silica, as well as the presence of ethoxy and/or silanol groups – either intact or formed due to hydrolysis of the ethoxy groups. Titrimetric and spectrophotometric analysis was performed to estimate the concentration of grafted SiH groups (in all samples prepared under fluidized bed conditions their concentration ranged within about 0.28–0.55 mmol/g as dependent on the reaction conditions). Other important aspects of fluidization such as the presence of solvent and/or hydrolyzing agent, bed heating mode and the effect of the silica sample thermal pre-treatment are also discussed.

An easy-to-process poly(silylene-acetylene) terminated by reactive ethynylphenyl: Synthesis, properties and composites

A series of telechelic silicon-containing hybrid polymers with reactive ethynylphenyl terminals were synthesized using the Grignard reagent method. The structure, processability, curing behavior, thermal stability and dielectric properties of the polymers, as well as the mechanical properties of carbon fiber reinforced composites at room temperature and high temperature, were well characterized. The results indicate that the ethynylphenyl-terminated poly(silylene acetylene)s (EPTSAs) have wide processing window and stable viscosity for 6 h at 70 °C. The cured EPTSAs exhibit excellent thermooxidative stabilities with temperatures of 5% weight loss (Td5) and the residues at 800 °C (Yr800). The thermal stability of the cured EPTSAs can increase markedly with incorporation of Si-H groups. The Td5 and Yr800 of the cured EPTSAs could reach to 601 °C and 52% in air, respectively. The pyrolysis behavior of cured EPTSAs elucidates the cure reactions and cross-linked networks. The cured resins show excellent dielectric properties in the frequency range of 10–106 Hz. Furthermore, the glass transition temperature of the cured EPTSAs do not arise before 500 °C. The flexural strength and modulus of the carbon fiber cloth (T300CF) reinforced EPTSAs composites could reach 252 MPa, and 42 GPa. The retention of mechanical properties of the composite at 300 °C can reach to 89%.

Porous Materials Based on Poly(methylvinylsiloxane) Cross-Linked with 1,3,5,7-Tetramethylcyclotetrasiloxane in High Internal Phase Emulsion as Precursors to Si-C-O and Si-C-O/Pd Ceramics

Polysiloxane networks were prepared by hydrosilylation of poly(methylvinylsiloxane) (V3 polymer) with 1,3,5,7-tetramethylcyclotetrasiloxane (D4H) at various Si-Vinyl: Si-H groups molar ratios in water-in-oil high internal phase emulsion (HIPE). Curing the emulsions followed by removal of water led to foamed cross-linked polysiloxane systems differing in the cross-linking degrees, as well as residual Si-H and Si-Vinyl group concentrations. Treatment of thus obtained materials in Pd(OAc)2 solution in tetrahydrofuran resulted in the formation of porous palladium/polymer nanocomposites with different Pd contents (1.09–1.70 wt %). Conducted investigations showed that pyrolysis of the studied materials at 1000 °C in argon atmosphere leads to porous Si-C-O and Si-C-O/Pd ceramics containing amorphous carbon and graphitic phases. Thermogravimetric (TG) analysis of the starting cross-linked polymer materials and those containing Pd nanoparticles revealed that the presence of palladium deteriorates thermal stability and decreases ceramic yields of preceramic networks. The extent of this effect depends on polymer cross-linking density in the system.

Reliable predictions of the net heat of combustion and the condensed phase heat of formation of organosilicon compounds

Two general correlations are introduced for reliable predicting the net heat of combustion and the condensed phase heat of formation of organosilicon compounds, which are essential for assessment of thermodynamic stability and risk assessment for loss prevention. The experimental values of the net heat of combustion of 145 of different types of organosilicon compounds are used to derive and test the new correlation, which is based on the contribution of some of the elemental composition and the number of –SiH3 group. The outputs of the net heat of combustion have also been used to calculate their condensed phase heat of formation. The high reliability of the two new models has been proved in comparison with several of the best quantitative structure–property relationships (QSPR) where they require complex descriptors. For 42 organosilicon compounds where the reported net heats of combustion by four recent complex QSPR models were available, the values of root-mean-square error (RMSE) of the new model and the best comparative model are 127.9 and 218.4 kJ mol−1, respectively. Moreover, the values of RMSE for the condensed phase heat of formation of the new model and the best complex QSPR model are 117.1 and 240.1 kJ mol−1, respectively.

Effective Approach to Render Stable Dynamic Omniphobicity and Icephobicity to Ultrasmooth Metal Surfaces.

Surface modifications for easy removal of liquids and solids from various metal surfaces are much less established than for silicon (Si) or glass substrates. Trimethylsiloxy-terminated polymethylhydrosiloxane (PMHS) is very promising because it can be directly immobilized covalently to a wide variety of metal surfaces by simply heating neat PMHS liquid, resulting in a film showing excellent dynamic omniphobicity. However, such PMHS films are easily degraded by hydrolytic attack in an aqueous environment. In this study, we have successfully improved the hydrolytic stability of the PMHS-covered ultrasmooth metal (Ti, Al, Cr, Ni, and Cu) surfaces by end-capping of the residual Si-H groups of the PMHS films with vinyl-terminated organosilanes, for example, trimethylvinylsilane (TMVS), through a platinum-catalyzed hydrosilylation reaction. The resulting TMVS-capped PMHS film surfaces showed significantly greater stability even after submersion in water for 6 days, with their excellent dynamic dewetting behavior toward water, toluene, n-hexadecane, and ethanol changing little. In addition, they also showed reasonable anti-icing (icephobic) properties with low ice-adhesion strength of less than 50 kPa even after 20 cycles of testing at -15 °C.