Search Results (281)

With the constant development of new polymer chemistry technologies, it is necessary to find modern synthetic pathways for the synthesis of polymers bearing numerous applicable characteristics, in an easy, efficient and environmentally friendly way. One such possibility is to present the use of metathesis type reactions and more specifically ring-opening metathesis polymerisation (ROMP), which provides the opportunity to produce linear unsaturated functionalised polymeric chains in a ‘living’ yet controlled manner with the use of ruthenium-based carbene (Ru=CHR) Grubbs’ catalysts (initiators: G1, G2, G3). In order to achieve satisfying results and obtain full conversion of the monomers, sterically hindered molecules are preferred, because the process of opening the ring results in simultaneous release of the energy that propagates the whole process. The incorporation of silicon-based substituents (such as silyl ethers) into the norbornene matrix can provide higher thermal stability of polymers, leading to the creation of flame-retardant materials. Other applications include gas separation membranes or biomedicine, upon further modification. This paper focusses on the development and optimisation of the synthetic method of previously not reported exo-norbornene silyl ethers along with their metathesis polymerisation to achieve linear unsaturated polymers with high isolation yields. Full article

N-Heterocyclic carbene (NHC) catalysis has emerged as a powerful and versatile strategy for constructing silicon derivatives, offering a metal-free alternative to traditional transition-metal methods. This review comprehensively summarizes recent advances in the NHC-catalyzed synthesis of organosilicon derivatives. Key transformations discussed include both asymmetric and non-asymmetric silylation reactions, as well as the construction of silicon-stereogenic centers. The content is systematically organized according to the types of silicon products and their underlying catalytic mechanisms. Our own perspectives on future development within this rapidly evolving field are also outlined. Full article

Silicone hydrogels offer high oxygen permeability but suffer from poor wettability. This study integrates a TRISS-based system (0–2.0 wt%) with a fixed PVP/NVP matrix (1.0/0.5 wt%) to enhance hydration-induced dimensional stability and surface properties. Fabricated via cast-molding, the lenses demonstrated that TRISS incorporation significantly enhances oxygen transport. Specifically, the 2.0 wt% TRISS formulation (S2.0) achieved an ~1.9-fold increase in oxygen-induced current (from 0.97 μA in pure-HEMA to 1.86 μA) while strongly suppressing hydration-induced swelling. To counter TRISS’s inherent hydrophobicity, the PVP/NVP matrix acted as a vital compensatory mechanism, driving the equilibrium contact angle down to 56.04° and avoiding the severe hydrophobic plateau (93.79°) of the additive-free comparator. S2.0 maintained a robust oxygen response alongside improved wettability. In conclusion, this system defines a workable low-silicone design window accommodating up to 2.0 wt% TRISS without wettability loss or optical degradation (>97%). Crucially, by leveraging TRISS to mitigate swelling-induced mechanical stress and PVP/NVP to ensure stable wettability, this structurally robust hydrogel provides a highly viable foundational matrix for future smart contact lenses equipped with diagnostic micro-components. Full article

Oxidative stress results from the excessive production of reactive oxygen species (ROS), which cause cellular and molecular damage and contribute to chronic diseases. Given the recognized antioxidant potential of benzimidazole derivatives—particularly 2-mercaptobenzimidazole—this study aimed to synthesize novel organosilicon S-silylalkylthioethers (I–IV) and N-alkylsilylthioethers (1a–3f) derived from this scaffold and to evaluate their antioxidant and antibrowning properties. The S-silylalkylthioethers were obtained by reacting 2-mercaptobenzimidazole with different chloroalkylsilanes under reflux in ethanol, followed by a reaction with alkyl halides in aprotic media at room temperature to prepare the N-alkylsilylthioethers. Structural elucidation was achieved through 1D and 2D NMR and FT-IR. Antioxidant activity was assessed using DPPH, the total antioxidant capacity, and ferric-reducing assays. The results showed several derivatives with notable antioxidant responses, revealing a clear relationship between carbon chain length, logP values, organosilicon substitution patterns, and radical-scavenging efficiency. Spearman correlation analysis further confirmed that DPPH activity is inversely related to total carbon number, molecular size, molecular weight, and LogP (ρ = −0.68 to −0.73, p < 0.001) and moderately negatively correlated with N-alkyl chain length (ρ = −0.47, p = 0.027), while S-alkyl chains showed no significant effect. These findings highlight the potential of these benzimidazole–organosilicon hybrids as antioxidant candidates and demonstrate how physicochemical properties govern their reactivity and antiradical capacity. Full article

An inorganic–organic hybrid nano-adsorbent was prepared by chemical immobilisation of an organic Schiff base Cu (II) ion receptor, DHB ((E)-N-(1-(2-hydroxy-6-methyl-4-oxo-4H-pyran-3-yl) ethylidene) benzohydrazide), a selective dehydroacetic acid-based chemosensor, onto a mesoporous silica support. In order to prepare the sorbent, the silylating agent was anchored onto the silica. During this procedure, 3-Chloropropyl trimethoxy silane (CPTS) was attached to the surface, increasing hydrophobicity. By immobilising DHB onto the CPTS platform, the silica surface was activated, and as a result the coordination chemistry of the Schiff base generated a hybrid adsorbent with the capability to rapidly sequestrate Cu (II) ions from wastewater, as an answer to combat growing Waste Electrical and Electronic Equipment (WEEE) contamination in water supplies, in the wake of a prolonged consumerism mentality and boom in cryptocurrency mining. The produced hybrid materials were characterised by FTIR, proximate and ultimate analysis, nitrogen physisorption, PXRD, SEM, and TEM. The parameters influencing the removal efficiency of the sorbent, including pH, initial metal ion concentration, contact time, and adsorbent dosage, were optimised to achieve enhanced removal efficiency. Under optimal conditions (pH 7.0, adsorbent dosage 3 mg, contact time of 70 min, and 25 °C), Cu (II) ions were quantitatively sequestered from the sample solution; 93.1% of Cu (II) was removed under these conditions. The adsorption was found to follow pseudo-second-order kinetics, and Langmuir model fitting affirmed the monolayer adsorption. Full article

The ruthenium-catalysed silylative coupling (SC) reaction is a useful method for obtaining selectively functionalised organosilicon compounds, which have a wide range of applications in organometallic and organic chemistry. It is possible to prepare such compounds with norbornene matrices, which can be used for ring-opening metathesis polymerisation (ROMP) in the synthesis of linear-type polymers. Herein, we present a method for the synthesis of the aforementioned matrices by a condensation reaction between diol and vinylphenylboronic acids. Furthermore, these compounds were subsequently modified by SC reaction and polymerised by ROMP. To assess the possibility of using styryl-based silyl-derived monomers as building blocks in further organic transformations, the process of bromodesilylation was also investigated. We would also like to perform a comparative study on the selectivity of hydrosilylation and silylative coupling processes in the case of discovered materials. Full article

Vinylallenes have been used in Diels–Alder reactions with a variety of dienophiles. However, vinylallenes activated at the allenic part of the molecule have been reacted only with carbon–carbon double bonds. We prepared siloxy vinylallenes by the base-induced equilibrium of silyl-protected allyl-propargyl alcohols. We found that these systems react with imines to form cycloadducts with total regio and facial selectivity, but only moderate endo:exo selectivity. The cycloadducts obtained were transformed into indolizidine derivatives. The reaction was studied computationally using DFT and compared to the reaction of siloxydienes. It was found that the main difference between those systems is the higher nucleophilicity of the siloxydienes compared to the siloxy vinylallenes. Full article

Hydroxy-functional poly(propenyl ether)s are promising thermoresponsive materials; here we establish a controlled synthesis via living cationic polymerization of silyl-protected monomers. Among the silyl protecting groups examined, only tert-butyldiphenylsilyl (TBDPS) enabled living cationic polymerization. The living cationic polymerization of tert-butyldiphenylsiloxybutyl propenyl ether (TBDPSBPE) afforded a high-molecular-weight polymer (poly(TBDPSBPE)) with a narrow molecular weight distribution (M_n = 12,900; M_w/M_n = 1.22). Additionally, chain propagation continued in monomer addition experiments, and the molecular weight increased further with a narrow molecular weight distribution, confirming the success of living cationic polymerization. Poly(TBDPSBPE) was successfully desilylated to afford poly(HBPE) with a narrow molecular weight distribution. Poly(HBPE) exhibited a glass transition temperature (T_g) of 44 °C, 82 °C higher than that of the corresponding polymer without β-methyl groups, poly(HBVE). The enhanced thermal properties of poly(HBPE) were attributed to the steric hindrance of the β-methyl group, which fixes the position of the hydroxy group and allows stronger hydrogen bonding. To investigate the aqueous thermoresponse, a hydroxylated analog with a shorter side-chain spacer (poly(HPPE)) was synthesized, and poly(HPPE) exhibited lower critical solution temperature (LCST)-type phase separation in water with a cloud-point temperature (T_cp) of 6 °C, showing reversible transitions with thermal hysteresis. Full article

This study investigates the effect of silylation and cellulose loading on the mechanical properties of epoxy composites. We use the hydrolyzed 3-Aminopropyltriethoxysilane (KH550) as a crosslinker for epoxy and as a coupling agent for cellulose. The mechanical properties of the epoxy composites are evaluated using molecular dynamics simulations. The improvement in the interfacial adhesion between epoxy and cellulose, achieved by using KH550, is demonstrated through the pulling out of cellulose from the epoxy composites. The results indicate that the nanocovalent bonds formed by KH550 at the epoxy/cellulose interface have a higher enhancement effect on the pulling force compared to increasing the cellulose content. For instance, the force needed for pulling 44.1 wt.% of raw cellulose is 93 ± 5 (kcal/mol)/Å, while the one required to pull the 28.1 wt.% of silylated cellulose is 97 ± 4 (kcal/mol)/Å. The silylated cellulose at 28.1 wt.% enhances the tensile modulus, shear modulus, and strength of the epoxy-KH550 composite by 14.55%, 15.65%, and 15.64%, respectively, compared to its counterpart reinforced with raw cellulose. Using the silylation treatment on cellulose that reinforces epoxy-KH550 at 43.9 wt.% improves the elastic modulus, shear modulus, and tensile strength of the epoxy composite by 4.23%, 4.64%, and 18.07%, respectively. Full article

β-Keto sulfides are a class of compounds containing both carbonyl (C=O) and thioether (C–S–C) functionalities, exhibiting significant potential in the field of medicinal chemistry. This study employs the silyl enol ether as the substrate, enabling the formation of C–S bonds under catalyst- and additive-free conditions, thereby facilitating the efficient synthesis of β-keto sulfides. The reaction proceeds rapidly and efficiently, exhibiting a broad substrate scope, and a total of 31 target compounds were synthesized with up to 95% yields. Full article

A series of half-titanocenes containing different trialkylsilyl para-phenoxy substituents, Cp*TiCl₂(O-2,6-ⁱPr₂-4-R-C₆H₂) [Cp* = C₅Me₅; R = Si(n-Bu)₃ (5), SiMe₂(n-C₈H₁₇) (6), SiMe₂(t-Bu) (7)], were prepared and identified. Catalytic activity in ethylene polymerization by Cp*TiCl₂(O-2,6-ⁱPr₂-4-R-C₆H₂) [R = H (1), SiMe₃ (2), SiEt₃ (3), Si(i-Pr)₃ (4), 5–7]–MAO (methylaluminoxane) catalysts increased in the following order (in toluene at 25 °C, ethylene 4 atm): R = H (1) < SiMe₃ (2), SiEt₃ (3), Si(i-Pr)₃ (4) < SiMe₂(t-Bu) (7) < SiMe₂(n-C₈H₁₇) (6) < Si(n-Bu)₃ (5, activity = 6.56 × 10⁴ kg-PE/mol-Ti·h). The results thus suggest that the introduction of an alkyl group into a silyl substituent led to an increase in activity. The activities of 5 were affected by the Al/Ti molar ratio (amount of MAO charged), and the highest activity (7.00 × 10⁵ kg-PE/mol-Ti·h) was observed under optimized conditions at 50 °C, whereas the activity decreased at 80 °C. In ethylene copolymerization with 1-dodecene, the Si(n-Bu)₃ analog (5) exhibited remarkable catalytic activity (4.32 × 10⁶ kg-polymer/mol-Ti·h at 25 °C), which was higher than those of the reported catalysts (1–3), affording poly(ethylene-co-1-dodecene)s with efficient comonomer incorporation as observed in 3 [r_E = 3.77 (5) vs. 3.58 (3)]. Full article

In the current study, the impact of different acaricide treatments against Varroa (such as amitraz strips, oxalic and formic acid strips impregnated with glycerin, or the sublimation or instillation of oxalic acid) on glycerol residue levels of propolis was investigated. Propolis samples were collected from five beehives located in Chalkidiki (northern Greece), where all mentioned treatments were used and chemically analyzed and compared to control ones. Propolis samples were collected on days 7, 21, and 65 after the application of Varroa treatments, extracted with ethanol/water (70:30), silylated, and then analyzed using GC-MS, showing the predominance of diterpenes. The sublimation of oxalic acid and the amitraz treatment yielded a low glycerol residue (5.12% and 5.09% from 9.98% and 9.19%, respectively) in propolis specimens, while glycerin-impregnated oxalic acid strips led to elevated glycerol percentages (24.30% from 20.51%), unlike the reduced glycerol residues for all other treatments (instillation: 12.60% from 14.48% and glycerin-impregnated formic acid strips: 8.91% from 9.25%) and controls (3.27% from 6.30%). Furthermore, Principal Component Analysis (PCA) and the corresponding biplot illustrated how the sample composition varied across treatments and sampling days, highlighting the chemical constituent categories that most strongly contributed to these distinctions. These findings suggest that the use of glycerol-impregnated strips should be avoided in future beekeeping treatments against varroosis, as they could have a negative impact on the quality of propolis either for nutritional or medicinal applications. Full article

Surface functionalization is a key enabler that imparts solid materials with excellent chemoselectivity. With this aim, halloysite and sepiolite clay particles were functionalized with carboxyethylsilanetriol sodium salt (CES) and 3-aminopropyltriethoxysilane (APTES), affording carboxy-terminated and amino-terminated clay, respectively. In the case of halloysite, the grafting occurs at Al-OH groups of the lumen surface (tube inner surface) and Al-OH and Si-OH groups at the edges and external surface defects of the nanotubes. For sepiolite, silanol groups located on the edges of the structural channels were at the origin of a chemical reaction between this fibrous clay and the terminal alkoxysilane. The resulting modified clays were examined for removal of Congo red (CR) and malachite green (MG) as anionic and cationic dyes, respectively. Clay bearing only carboxylic groups display more affinity towards cationic dye (MG), recording 926 mg·g⁻¹ and 387 mg·g⁻¹ for HNT-CES and SEP-CES, respectively, while amino-functionalized clays show very high adsorption for anionic dye (CR), reaching 1232 and 1228 mg·g⁻¹ for HNT-APTES and SEP-APTES, respectively. Simultaneous grafting of the two silyl coupling reagents was also attempted through one-pot and sequential grafting method, with the latter being more appropriate to access amphoteric clay featuring both carboxylic and amino groups. The behavior of the bifunctional adsorbents was investigated with respect to pristine and monofunctional clay. The obtained results provide insights to fulfill the requirement for handling complex water effluent containing both anionic and cationic pollutants, towards more sustainable development. Full article

Amino acids (AAs), a type of nitrogen-based organic compounds in the atmosphere, are directly and indirectly related to climate change, and as their link to allergic diseases becomes more known, the need for quantitative analysis of ultrafine dust (PM_2.5) will become increasingly necessary. When sensing water-soluble AAs using a gas chromatograph combined with a tandem mass spectrometer (GC-MS/MS), derivatization should be considered to increase the volatility and sensitivity of target analytes. In this study, two methods were used to compare and evaluate 13 AA derivatives in PM_2.5 samples: N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide with 1% tert-butyldimethylchlorosilane (MTBSTFA w/1% t-BDMCS), which is preferred for silylation, and ethyl chloroformate (ECF) with methanol (MeOH) for chloroformate derivatization. The most appropriate reaction conditions for these two derivative methods, such as temperature and time, and the analytical conditions of GC-MS/MS for the qualitative and quantitative analysis of AAs were optimized. Furthermore, the calibration curve, detection limit, and recovery of both methods for validating the quantification were determined. The two derivative methods were applied to 23 actual PM_2.5 samples to detect and quantify target AAs. The statistical significances between pairwise measurements of individual AAs detected by both methods were evaluated. This study will help in selecting and utilizing appropriate derivative methods for the quantification of individual AAs in PM_2.5 samples. Full article