Dehydration Condensation Research Articles

MoS2 functionalized lithium complex soap with enhanced thickening net structure toward high-performance thickener

A crucial prerequisite for obtaining high performance interface lubrication is to regulate the composition and structure of thickener for grease, confronting fatal friction and loss issues in significant equipment manufacturing industrial clusters. Here, a structural defect-mediated transplantation of l-cysteine onto MoS2 nanosheets was outlined, utilizing mechanical stress induction and mercaptan chemical guidance technology to fully exploit the S vacancies and active Mo atom conjugation. A new MoS2 functionalized lithium complex thickener (CLT/MoS2) was constructed with eutectic hydrogen-bond thickening system. DFT calculation confirmed that MoS2-NH2 reacted with the carboxyl located at dodecyl stearic acid via dehydration condensation. The regulated-grease using CLT/MoS2 as thickener in synthetic oil significantly reduced the friction and wear, owing to the formation of complex hydrogen-bond thickening network and induced transition of lubrication state as well as the formation of MoS2-based tribo-chemical films. This research introduces a novel approach to the creation of high-performance grease by deploying functional thickener to weaken the wear hazards.

Recycling of hazardous jarosite residues based on hydrothermal crystal transformation

Jarosite [MeFe3(SO4)2(OH)6] is a typical non-ferrous smelting slag produced in the process of iron removal from hydrometallurgical solution, which contains a large number of valuable and toxic metal elements. Treating the complex and hazardous jarosite residue in an economically and environmentally sound way has always been an urgent problem. A novel one-step hydrothermal treatment method was proposed in this paper for recycling of jarosite residues. It can be seen from the XRD and TEM results that jarosite residues could be completely transformed into hematite crystal particles under hydrothermal conditions at temperature above 220℃. Meanwhile, other valuable metal components (such as nickel sulfate hexahydrate) entrained in the residue will be dissolved in the aqueous solution, which can be reused in the hydrometallurgical process. Through phase composition analysis of the hydrothermal process, it is concluded that jarosite was firstly pyrolyzed to generate Fe3+. The obtained Fe3+ was then hydrolyzed to Fe (OH)3, which was transformed into Fe2O3 through dehydration condensation and directional arrangement. Further roasting the hematite particles, the obtained product contained 62.57 % of Fe, but only 0.21 % of S and 0.04 % of As, which meets the requirements of raw materials for iron making. In addition, compared with the current international standard ISO 1248:2006 (E), the obtained hematite particles with nanometer size and single crystal structure can be used as iron oxide red pigment. Overall, the one-step hydrothermal treatment of jarosite residues followed by reduction roasting not only realizes the economic recycling of the metal resources, but also solves the stacking problem of those hazardous residues.

The impact of H-ZSM-5 catalyst on the mechanism of fuel-N conversion during glutamic acid pyrolysis

During the pyrolysis of biomass, Fuel-bound Nitrogen (Fuel-N) is converted into N-containing compounds present in bio-oil and biochar. These compounds are easily oxidized into NOx during subsequent utilization, causing ecological damage. Catalytic fast pyrolysis has emerged as a promising method for denitrogenation in recent years, but the underlying catalyst mechanism still needs to be determined. This study analyzed the impact of catalyst H-ZSM-5 on the mechanism of Fuel-N conversion during the pyrolysis of glutamic acid, a model compound for nitrogenous biomass, through experimental studies and theoretical calculations. According to literature data, the pyrolysis of glutamic acid predominantly yielded the N-containing products pyrrole, glutarimide, and pyrrolidone. The H-ZSM-5 catalyst showed optimum denitrification at 600 ℃, resulting in a 49.62% reduction in the proportion of N-containing compounds. In the catalytic pyrolysis products, the generation of toluene and naphthalene increased. In-situ DRIFTS experiments were consistent with the results of Py-GC-MS experiments, with catalytic pyrolysis promoting deaminations and decarboxylations, decreased imines and nitriles, and increased aromatic hydrocarbons. Additionally, the energy barrier changes of each pyrolysis pathway were calculated based on Density Functional Theory (DFT). The results showed that the H-ZSM-5 catalyst primarily promoted the deamination reaction, followed by the decarboxylation and dehydration condensation reactions, while inhibiting the dehydrogenation reaction. Moreover, the energy barrier for unsaturated hydrocarbon addition reactions was reduced, facilitating the formation of aromatic compounds. The acid sites inside the H-ZSM-5 catalyst weakly interacted with the reactants, making it easier to detach the amino group during catalytic pyrolysis. This study provides a reference for the denitrification of bio-oil and biochar. Subsequent work can realize the regulation of nitrogen conversion by changing the acidity and concentration of catalyst acid sites.

Effect of the Chemical Properties of Silane Coupling Agents on Interfacial Bonding Strength with Thermoplastics in the Resizing of Recycled Carbon Fibers

Upcycling recycled carbon fibers recovered from waste carbon composites can reduce the price of carbon fibers while improving disposal-related environmental problems. This study assessed and characterized recycled carbon fibers subjected to sizing treatment using N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (APS) chemically coordinated with polyamide 6 (PA6) and polypropylene (PP) resins. Sizing treatment with 1 wt.% APS for 10 s yielded O=C-O on the surface of the carbon fiber, and the -SiOH in the APS underwent a dehydration–condensation reaction that converted O=C-O (lactone groups) into bonds of C-O (hydroxyl groups) and C=O (carbonyl groups). The effects of C-O and C=O on the interfacial bonding force increased to a maximum, resulting in an oxygen-to-carbon ratio (O/C) of 0.26. The polar/surface energy ratio showed the highest value of 32.29% at 10 s, and the interfacial bonding force showed the maximum value of 32 MPa at 10 s, which is about 15% better than that of commercial carbon fiber (PA6-based condition). In 10 s resizing treatments with 0.5 wt.% 3-methacryloxypropyltrimethoxysilane (MPS), C-O, C=O, and O=C-O underwent a dehydration–condensation reaction with -SiOH, which broke the bonds between carbon and oxygen and introduced a methacrylate group (H2C=C(CH3)CO2H), resulting in a significant increase in C-O and C=O, with an O/C of 0.51. The polar/surface free energy ratio was about 38% at 10 s, with the interfacial bonding force increasing to 27% compared to commercial carbon fiber (PP-based conditions). MPS exhibited a superior interfacial shear strength improvement, two times higher than that of APS, with excellent coordination with PP resin and commercial carbon fiber, although the interfacial bonding strength of the PP resin was significantly lower.

Novel Carboxylation Method for Polyetheretherketone (PEEK) Surface Modification Using Friedel–Crafts Acylation

Recently, polyetheretherketone (PEEK) has shown promising dental applications. Surface treatment is essential for dental applications owing to its poor surface energy and wettability; however, no consensus on an effective treatment method has been achieved. In this study, we attempted to carboxylate PEEK sample surfaces via Friedel–Crafts acylation using succinic anhydride and AlBr3. The possibility of further chemical modifications using carboxyl groups was examined. The samples were subjected to dehydration–condensation reactions with 1H,1H-pentadecafluorooctylamine and N,N’-dicyclohexylcarbodiimide. Furthermore, the sample’s surface properties at each reaction stage were evaluated. An absorption band in the 3300–3500 cm−1 wavenumber region was observed. Additionally, peak suggestive of COOH was observed in the sample spectra. Secondary modification diminished the absorption band in 3300–3500 cm−1 and a clear F1s signal was observed. Thus, Friedel–Crafts acylation with succinic anhydride produced carboxyl groups on the PEEK sample surfaces. Further chemical modification of the carboxyl groups by dehydration-condensation reactions is also possible. Thus, a series of reactions can be employed to impart desired chemical structures to PEEK surfaces.

Immobilizing graphitic carbon nitride on porous silica via hydrogen bonds for photocatalytic flow synthesis of azoxybenzene

Heterogeneous photocatalysis is an ideal method for eco-friendly synthesis of value-added chemicals. However, due to the limited penetration depth of photons and inefficient utilization of the catalytic active sites, the scalability of heterogeneous photocatalysis is restrained. Combining heterogeneous photocatalysis and flow system is a promising solution to optimize the light absorption and mass transfer; however, an affordable, practical design of the flow system and the immobilization method of the photocatalyst is still missing. Here, we report a flow system for heterogeneous photocatalytic synthesis of azoxybenzene and its derivatives from reductive coupling of nitrobenzene at a gram-scale using anchored graphitic carbon nitride (gCN) on porous silica (gCN-SiO2). The hydrogen bonds formed between the gCN and the tetramethoxysilane (TMOS) precursor during the dehydrative condensation process prevent unwanted leaching of catalyst, enabling photocatalytic flow synthesis of azoxybenzene with high selectivity, efficiency, and durability. Mechanistic studies reveals that the gCN-SiO2 regulates the photocatalytic reduction kinetics of nitrobenzene by facilitating the generation of nitrosobenzene and N-phenylhydroxylamine intermediates while preventing the formation of unwanted 4-phenylazophenol byproducts, resulting in efficient and selective synthesis of azoxybenzene. Our work provides an alternative path towards large scale heterogeneous photocatalysis.

Synthesis of a new three-dimensional cross-linked network dust suppressant and its mechanism of coal-dust inhibition

A new dust suppressant was proposed and studied by numerical calculations and experiments to control dust. The synthesis of suppressant required three steps. First, Polyvinyl alcohol starch was synthesized by the dehydration condensation of carboxymethyl starch and polyvinyl alcohol under the initiation of ammonium persulfate, requiring 288.8 kJ/mol energy. Second, polyvinyl alcohol caprolactam starch was synthesized by the dehydration condensation of caprolactam and polyvinyl alcohol starch under the initiation of ammonium persulfate, requiring 172.8 kJ/mol of energy. Third, the suppressant had the optimum wetting and bonding effects by 30 g/L polyvinyl alcohol caprolactam starch and 20 g/L sodium dodecylbenzene sulfonate. The suppressant–lignite system exhibited increased hydrogen bonds which were formed between the –OH and –COOH groups of the suppressant and the –OH, –COOH, and –NH2 groups on the coal surface. The solidified layer formed on the coal dust surface did not raise dust at wind speed of 10 m/s.

A green versatile packaging based on alginate and anthocyanin via incorporating bacterial cellulose nanocrystal-stabilized camellia oil Pickering emulsions

This study aims to develop a versatile intelligent packaging based on alginate (Alg) and anthocyanin (Ant) by incorporating bacterial cellulose nanocrystal-stabilized camellia oil Pickering emulsions. Firstly, bacterial cellulose nanocrystals (BCNs) matrix produced from kombucha was incorporated with camellia oil into via ultrasonic triggering, forming a stable and multifunctional camellia oil-bacterial cellulose nanocrystal Pickering nanoemulsions (CBPE). The microstructure and rheology results of the emulsion confirmed the stabilized preparation of CBPE. Subsequently, the CBPE was integrated into the three-dimensional network structure composed of alginate/anthocyanin. The composite film (Alg-Ant-CBPE) was designed through Ca2+ crosslinking, intermolecular hydrogen bonding and dehydration condensation. The fabricated color indicator films with different concentrations of CBPE (0.1 %–0.4 %), showed varying degree of improvement in hydrophobicity, UV shielding, mechanical strength, thermal stability, water vapor barrier properties and antioxidant capacities. When applied to yogurt, the Alg-Ant-CBPE4 exhibited more pronounced color changes compared to Alg-Ant, enabling visual detection of food freshness. In conclusion, the incorporation of Pickering nanoemulsion provides an effective and promising approach to enhance the performance of polysaccharide-based intelligent packaging.

Quaternary ammonium silane modified Nanolime for the consolidation and antifungal of stone relics

Cultural relics such as wall paintings and stone relics face a decrease in mechanical strength and contamination from microbial growth. Nanolime (NL), as an exceptional inorganic nanomaterial used in the consolidation of cultural heritages, has been investigated for more than two decades. However, it has limited antibacterial properties. Here, we opted for dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DC5700) to modify the surface of NL particles, praparing an organic–inorganic hybrid nanomaterial (NL-DC5700) that provides long-lasting antifungal effects for stone samples without sacrificing its consolidation effect. Characterizations demonstrate that DC5700 grafts onto the surface of NL particles through the formation of covalent bonds via dehydration condensation between the siloxane of DC5700 and the hydroxyl of NL, forming an organic shell layer that uniformly wraps the NL particles. NL-DC5700 can endow stone samples with near superhydrophobicity (NL, 25.4° and NL-DC5700, 142.0°) and durable antifungal effects over 90 days, superior to those of pure NL. NL-DC5700 shows no unacceptable impact on the appearance, porosity, or microstructure of the stone specimens. Our work explores the antifungal effect of NL-based materials and provides fresh insights into the development of versatile conservation materials for stone relics.

Study on a nano-porous gold/polyamidoamine (NPG/PAMAM)-based electrochemical aptamer biosensor for the detection of ochratoxin a in the red wine

In this study, a novel electrochemical aptamer sensor for detecting ochratoxin A (OTA) was constructed. First, a gold-copper alloy film was prepared via electrochemical deposition, and copper was selectively dissolved in constant potential mode for obtaining the nano-porous gold modified screen-printed carbon electrodes (NPG/SPCE). Then, 2-mercaptoethylamine was dropped on the NPG/SPCE surface and Au-S covalent bonds were formed for immobilizing the metal. Glutaraldehyde as cross-linking agent was added, which resulted in immobilization and attachment of PAMAM to the 2-mercaptoethylamine through the dehydration condensation reaction. During the preparation process, the nano-porous gold and PAMAM-modified layers were characterized by SEM, XRD, and IR spectroscopy, respectively. The characterization results showed that the nano-porous gold and PAMAM composite films were successfully modified. Finally, the OTA aptamer was cross-linked with PAMAM by glutaraldehyde to complete construction of the Apt/PAMAM/NPG/SPCE sensor. The electrochemical performance of this sensor was tested in ochratoxin A solutions with the DPV method. The results showed that the sensor’s reproducibility, stability, and specificity were good. The spiked recoveries in red wine ranged from 99.65%∼101.6%, with a linear range of 0.5 ng/mL∼20 ng/mL and a minimum detection limit of 0.141 ng/mL. Thus, the novel biosensor may provide a promising tool for the trace detection of OTA.

High-loading of organosilane-grafted carbon dots in high-performance luminescent solar concentrators with ultrahigh transparency

Carbon dots (CDs) generally suffer from aggregation-induced fluorescence quenching effect in solid-state, which significantly limits their application in photoelectric devices. Due to this effect, it is a great challenge to achieve high-transparency and high-performance luminescent solar concentrators (LSCs) based on CDs. Here, the synthesis of organosilane-grafted carbon dots (Si-CDs) is rationally designed by hydrothermal method using anhydrous citric acid, ethanolamine and KH-792 as the reaction precursors. The obtained Si-CDs can be uniformly dispersed in the polyvinyl alcohol (PVA) matrix through the dehydration condensation reaction and hydrogen bonding between the silicon hydroxyl group of Si-CDs and the hydroxyl group of PVA. Based on this property, Si-CDs/PVA thin-film LSCs (5 ×5 ×0.2 cm3) with ultrahigh CD loading (25 wt%) and high transparency can be fabricated, exhibiting excellent absorption in the UV spectral region and about 90 % transmission in the visible range. Furthermore, the power conversion efficiency (PCE) of the LSCs can reach 2.09 % under a standard solar light and shows excellent stability even over 12 weeks. This synthetic design is expected to be beneficial for future development of CD synthesis and paves the way for the development of CDs-based photoelectric devices.

Revealing the Structure of Tryptophan in Microhydrated Complexes by Cold Ion Spectroscopy.

The geometry of biomolecules isolated in the gas phase usually differs substantially from their native structures in aqueous solution, which are the only ones truly relevant to life science. To connect the high resolution of cold ion spectroscopy that can be achieved in the gas phase and the key role of intermolecular hydrogen bonds that shape biomolecules in water, we study protonated tryptophan microhydrated by 1-6 water molecules. IR/UV spectra measured with the same instrument under similar conditions appear to be identical for the complexes of the same size produced by soft dehydration and cryogenic condensation methods. This observation points to the lack of kinetic trapping in the dehydration/rehydration processes. Quantum chemistry computations allow for the unambiguous assignment of the measured IR spectra to the most stable conformers of the complexes. The calculations reveal that retaining as few as four water molecules still conserves most of the TrpH+ native structural features.

Cu(II)-Catalyzed Cascade of N-Phenyl-o-phenylenediamine with Benzaldehyde: One-Step Direct Construction of 2-(1-Phenyl-1H-benzo[d]imidazol-2-yl)phenols.

A practical protocol for the construction of hydroxylated 2-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenols (PBIs) from N-phenyl-o-phenylenediamine with benzaldehydes was developed. The cascade reaction was enabled by heating a mixture of the two substrates in the presence of air as an oxidant and anhydrous Cu(OAc)2 as a catalyst in dimethyl sulfoxide, and a diverse series of PBIs were synthesized in moderate to good yields (69-81%). Furthermore, the synthesis of the PBIs was enabled via a one-pot cascade reaction that proceeded through subsequent dehydration condensation, intramolecular cyclization, and aromatic C-H hydroxylation. This protocol can be used for the synthesis of hydroxylated PBI via a one-pot annulation C-H hydroxylation reaction rather than through a series of multistep reactions, which provides the possibility of further modification.

Synthesis of N-Unprotected Diaryl Ketimines and Alkyl Ketimines from Ketones and Ammonia Using Porous Solid Acids with Analysis of Their Adsorption Behavior

Abstract The most atom-efficient synthetic method for N-unprotected ketimines (N-H ketimines) from ketones is the dehydration condensation reaction with ammonia (NH3). However, until now, few synthetic methods for N-H ketimines with high versatility have been known. In this study, we examined various solid acids and found that N-H diaryl ketimines with various functional groups on the aryl groups could be synthesized in high yields from diaryl ketones and NH3 under solvent-free conditions using silica-alumina (SiO2-Al2O3) or proton-exchanged Y-type zeolite (H-Y). Solid-state 13C and 15N NMR measurements indicated that the N-H ketimine formed in the pores of acidic zeolite was coordinated to NH4+ species on the pore surface. By quantum chemical calculations we also discussed the reason why the dehydration-condensation reaction between ketone and NH3, which is an endothermic reaction in a vacuum, was biased toward the product side in the actual experiment. In addition, this synthetic method can be applied to synthesize N-H alkyl ketimines with α-acidic hydrogens, which are less stable and more sensitive to hydrolysis and oligomerization than diaryl ketimines.

Multifunctional sustainable films of bacterial cellulose nanocrystal-based, three-phase pickering nanoemulsions: A promising active food packaging for cheese

Owing to increasing plastic pollution and concerns about food safety, extensive research attention has been paid to biodegradable active packaging. Herein, we developed bacterial cellulose nanocrystal (BCN)-based three-phase Pickering nanoemulsion gelatin (GL) films. In detail, bacterial cellulose was obtained using Acetobacter xylinum, which was then hydrolyzed using sulfuric acid to prepare BCNs. Carnosic acid (CA) and ε-polylysine (εPL) were incorporated into the BCN matrix through electrostatic complexation and the matrix was ultrasonically triggered as an emulsification self-assembly strategy, forming the multifunctional BCN-based three-phase O/W Pickering nanoemulsions (CA-εPL PEs). Furthermore, a novel active packaging film (GL-CA-εPL PEs) was designed via intermolecular hydrogen bonding and dehydration condensation by introducing CA-εPL PEs into the 3D network structures of a GL matrix; both phases showed good interaction and compatibility, along with excellent antioxidant, antibacterial, UV-shielding, good mechanical, heat-sealing, sustainable release, and biodegradable properties. Additionally, fresh (acid-coagulated) and mozzarella cheese were packed in the GL-CA-εPL100 PE film, and their shelf life was extended due to delayed lipid peroxidation and inhibition of the growth of spoilage microorganisms. Sensorial and flavored (GC-IMS) analyses showed no significant differences between the samples packed in the GL-CA-εPL100 PE active film and the unpacked samples. This study provides scientific insights for designing BCN-based O/W multifunctional three-phase Pickering nanoemulsion delivery systems for active food packaging; the proposed method can be promising for reducing the environmental impact of plastic pollution.

Temperature-Sensitive Modified Bentonite Based on NIPAM for Drilling Fluid: Experimental and Molecular Simulation Studies.

Bentonite is an important component of drilling fluid, whose quality directly affects the safety and economic benefits of water-based drilling fluid. In order to effectively cope with temperature changes, the development of temperature-sensitive modified bentonite is of great significance. In this study, a temperature-sensitive modified bentonite based on NIPAM with excellent temperature sensitivity was developed through intercalation modification. The temperature-sensitive bentonite (CMC-B-NIPAM) was prepared by grafting N-isopropyl acrylamide (NIPAM) onto the surface of calcium bentonite through the dehydration condensation of silane coupling agent KH570 after the intercalation of sodium Carboxymethyl Cellulose (CMC). The synthesis indexes of CMC-B and CMC-B-NIPAM were optimized by the single-factor method. CMC-B-NIPAM was characterized by XRD and FTIR. The temperature sensitivity, rheology, suspensibility, and expansion capacity of CMC-B-NIPAM dispersion were investigated. The results showed that CMC-B-NIPAM had good temperature sensitivity, and the rheological properties of its dispersion showed characteristics of steady flow and temperature thickening in the range of 40-70 °C. A molecular simulation model was established to observe the microsynthesis mechanism of temperature-sensitive modified bentonite based on NIPAM. The results of this study show that CMC-B-NIPAM drilling fluid has the function of ensuring the stability of drilling fluid flow patterns compared to traditional drilling fluids.

N–N Bond Formation by a Small-Ring Phosphine Catalyst via the PIII/PV Cycle: Mechanistic Study and Guidelines to Obtain a Good Catalyst

The mechanism of the N–N cross-coupling of nitroarene and aniline catalyzed by 1,2,2,3,4,4-hexamethylphosphetane oxide (1PO) as well as the prediction of a better catalyst was theoretically investigated using DFT and DLPNO-CCSD(T) calculations. An active species 1P is generated through deoxygenation of 1PO by diphenylsilane. Then, 1P extracts one oxygen atom from nitroarene to produce nitrosoarene. In this deoxygenation step, the [3 + 1] cheletropic addition is a rate-determining step with the ΔG0≠ and ΔG0 values of 28.8 and −7.3 kcal/mol, respectively. Next, nitrosoarene exclusively undergoes a dehydrative condensation reaction with aniline to form an azo-cation intermediate, which is the origin of the high selectivity in this cross-coupling reaction. In this step, 2,4,6-trimethylbenzoic acid plays an essential role to significantly reduce the ΔG0≠ value from 41.1 to 14.8 kcal/mol. Subsequently, 1P reacts with the azo cation to form a stable hydrazinylphosphonium species through the nucleophilic attack of the phosphorus atom to the cationic nitrogen atom. The phosphonium center preferably accepts a hydroxyl group from water to ensure the formation of hydrazine in the subsequent step. In the [3 + 1] cheletropic addition step, the highest occupied molecular orbital (HOMO) of 1P plays an important role. The small-ring scaffold of 1P raises the HOMO energy compared to acyclic phosphorus compounds to achieve high activity of 1P. Substitution of a dimethylamino group for the methyl group in 1P was theoretically predicted to improve the activity by further increasing the HOMO energy.

Regiospecific Formal [3+2] Annulations of α‐keto Sulfines and N‐Substituted Thioureas

AbstractA series of 2,4‐dithiohydantoins were synthesized regiospecificlly from various phenacyl sulfoxides bearing 1‐methyl‐1H‐tetrazole and N‐substituted thioureas in moderate to excellent yields. The proposed mechanism involved the generation of α‐sulfines from sulfoxides through thermolytic elimination, carbonphilic attack of sulfines by substituted thioureas, and dehydration condensation. The current method provides a safe strategy for the preparation of 2,4‐dithiohydantoins.

Multiscale analysis of silane coupling agent modified rubber-fiber concrete interfaces

This study employs PVA fibers to improve the performance of rubber concrete and silane coupling agent to change the incompatibility between rubber and cement in order to weaken the issue of a weak interfacial transition zone between rubber and cement foundation (KH570). The results showed that 1.5% content of KH570 modified 15% content of rubber-1.5% content of PVA fiber with the best effect. KH570 was identified using XRD, FTIR, and SEM characteristics. It was discovered that KH570 experienced a dehydration condensation reaction with free or adsorbed water in the cement, which helped to maintain the integrity between the cement matrix and the rubber. It strengthened the bond between the cement, the rubber, and the PVA fibers and enhanced the cement's capacity to encapsulate the rubber. Finally, molecular dynamics simulations reveal that cement and rubber are connected by Si-O-Si and molecules appear to be cross-distributed, increasing interfacial compatibility and reducing interfacial effects. It can be clearly observed in the interfacial bonding mechanism that KH570 is mainly a C-S-H matrix with parallel or perpendicular connections at the tail end.

An Improvement of Mechanical Properties of Two Kinds of Silicone Resins Containing Ladder Segments by Chemical Modification with Trimethylborate.

We suggest a new method for postsynthesis modification of silicones containing silanol groups. It was found that trimethylborate is an effective catalyst for dehydrative condensation of silanol groups with the formation of ladder-like blocks. The utility of this approach was demonstrated on postsynthesis modification of poly-(block poly(dimethylsiloxane)-block ladder-like poly(phenylsiloxane)) and poly-(block poly((3,3',3″-trifluoropropyl-methyl)siloxane)-block ladder-like poly(phenylsiloxane) with a combination of linear and ladder-like blocks having silanol groups. The postsynthesis modification leads to a 75% increase in tensile strength and 116% elongation on break in comparison with the starting polymer.