• Journal of the Korean Chemical Society
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• v.68 no.2
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• pp.74-81
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• 2024

A sulfonic acid-water-silanol system in SO₃H-functionalized MCM-41 was investigated using solid-state nuclear magnetic resonance techniques. The proton exchange rate between a water molecule and a silanol group in the S-PE-MCM-41 was determined by analyzing the 1D proton spectra, the proton EXSY spectrum, and ²H spin-lattice relaxation data under various hydration levels. Two kinds of water-bounding sites were found in the S-PE-MCM-41: weakly and strongly bound sites. Over several hours, water molecules bound to the weakly bound sites at the low hydration level migrated to the strongly bound sites. At high temperature, the S-PE-MCM-41 easily lost water molecules weakly bound to the silanol, while the strongly bound water molecules survived. Water molecules that participated in the hydration of the phenethyl sulfonate were involved in the hydrogenbonded silanol mechanism of proton conductivity. This phenomenon contributes higher proton conductivity to the S-PE-MCM-41 by the cooperation of sulfonyl and silanol groups in the proton transfer process, even at higher temperature.

• Elastomers and Composites
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• v.47 no.1
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• pp.54-64
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• 2012

Acrylonitrile was introduced in the emulsion SBR to increase compatibility between silica and rubber. AN-SBR/silica compounds showed faster vulcanization time and higher delta torque values than SBR 1721/silica compounds because interaction between nitrile group of AN-SBR and silanol group on the silica surface could make hydrogen bond that prevented adsorption of the accelerator on the silica surface, which improved the vulcanization reaction efficiency and enhanced the degree of crosslinking. AN-SBR/silica compound showed higher values in minimum torque than SBR 1721/silica compound during the vulcanization because AN-SBR has higher molecular weight than SBR 1721 in the raw material. When PEG was added to the SBR 1721 and AN-SBR compounds, vulcanization time was faster than SBR 1721 and AN-SBR compounds without PEG because PEG has a large number of ether linkages which show high compatibility with silanol group on the silica surface that prevented the adsorption of the accelerator and the ingredients on the silica surface, which improved the vulcanization reaction efficiency. In the mechanical properties, AN-SBR compounds showed higher modulus values at 100%, 300% than SBR 1721 compounds because interaction between nitrile group of AN-SBR and silanol group on the silica surface enhanced the degree of crosslinking. In the dynamic properties, AN-SBR compounds showed lower tan ${\delta}$ values at $0^{\circ}C$ than SBR 1721 compounds in accordance with the $T_g$ values. AN-SBR compounds showed lower tan ${\delta}$ values at $60^{\circ}C$ than SBR 1721 compounds because interaction between acrylonitrile and silica caused strong filler-rubber interaction that induced low energy dissipation by the filler-filler interaction.

• Elastomers and Composites
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• v.50 no.3
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• pp.159-166
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• 2015

Silica which is used for reinforcing filler in tire industry is widely known as eco-friendly material exerting $CO_2$ reduction effect through decrease of rolling resistance and improvement of wet grip. Generally silica is classified as a highly polar filler because it contains a large number of silanol (Si-OH) group on its surface. And also silica gives a lower reinforcing effect than carbon black due to its poorer rubber-filler interaction. Therefore silica is treated with silane coupling agent or activator, then following the conventional rubber blend method, vulcanized sheets were prepared using a hot press, and cure characteristics, mechanical properties and abrasion resistance of the test specimens were investigated. It was found that with an increase in the silane coupling agent content the tensile strength, 300% modulus and abrasion resistance increased while Mooney viscosity decreased and crosslink density slightly increased with an increase of activator.

• Journal of the Korean Chemical Society
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• v.19 no.5
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• pp.317-324
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• 1975

The adsorptions of gaseous $H_2O\;and\;D_2O\;on\;Na^+-,\;Ca^{2+}-,\;and\;Al^{3+}$ montmorillonites at various temperatures were undertaken. Break down of ir hydroxyl stretching bands into four Gaussian components was made by means of manual technique. Resonance theory of water to form silanol hydroxyl group was supported by $3625cm^{-1}$ band for OH and $2680cm^{-1}$ band for OD which depend on amounts of water adsorbed. The broad bands at about $3400 cm^{-1}\;and\;2475cm^{-1}$ were assigned to stretching band of silanol OH hydrogen bonded to adsorbed water. The prominent $3230 cm^{-1}$ band together with component around $2345 cm^{-1}$ were attributed to adsorbed $H_2O\;and\;D_2O$ respectively. The chemical nature of the hydrogen bonding between adsorbed water and neighboring surface OH was explained adequately in terms of electrostatic interaction.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3196-3202
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• 2012

Post-synthesis is used to synthesize organic hybrid inorganic mesoporous sieves. In this method, the activity and structure of the base sieve are crucial to obtain the definable hybrid materials. The chemical and physical properties of the base can be largely changed either by the final step of its synthesizing processes, by template removal which is accomplished with the oxidative thermal decomposition (burning) method or by solvent extraction method. In this paper we compared two methods for the post-synthesis of organic hybrid MCM-48. When the template was extracted with HCl/alcohol mixture, the final product showed larger pore size, larger pore volume and better crystallinity compared to the case of the thermal decomposition. The reactivity of the surface silanol group of template free MCM-48 was also checked with an alkylsilylation reagent $CH_2=CHSi(OC_2H_5)_3$. Raman and $^{29}Si$ NMR spectra of MCM-48 in the test reaction indicated that more of the organic group was grafted to the surface of the sample after the template was removed with the solvent extraction method. Direct synthesis of vinyl-MCM-48 was also investigated and its characteristics were compared with the case of post-synthesis. From the results, it was suggested that the structure and chemical reactivity can be maintained in the solvent extraction method and that organic grafting after the solvent extraction can be a good candidate to synthesize a definable hybrid porous material.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.685-691
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• 2009

Dispersions of fumed silica are made in 6 kinds of mono-solvents and mixed solvents which have hydroxyl group, non hydroxyl group, different polarity, and different molecular size. The viscosity and rheology behaviors of the each dispersion are investigated according to the viewpoint of solvent characteristic. The silica dispersion in polar solvent with hydroxyl group is stable and low viscous sol. The silica dispersion in non-polar solvent with non-hydroxyl group is high viscous gel. When the solvent with hydroxyl group is added to the silica dispersions with non-polar solvents, they show the reduction of viscosity with solvent content. They have minimum critical content which shows no viscosity change. The minimum critical solvent content is decreased according to the polarity of solvents with no hydroxyl group. The solvation layer which is formed on the silica surface through hydrogen bonding between hydroxyl-containing solvent and the silanol group of silica surface is the reason of stable and low viscous sol. In case of non-polar solvent, silanol on adjacent silica particles interacted directly by hydrogen bonding show high viscous and flocculated gel.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.4
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• pp.427-438
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• 2023

Thermodynamic sorption modeling can enhance confidence in assessing and demonstrating the radionuclide sorption phenomena onto various mineral adsorbents. In this work, Ca-montmorillonite was successfully purified from Bentonil-WRK bentonite by performing the sequential physical and chemical treatments, and its geochemical properties were characterized using X-ray diffraction, Brunauer-Emmett-Teller analysis, cesium-saturation method, and controlled continuous acid-base titration. Further, batch experiments were conducted to evaluate the adsorption properties of Cs(I) and Sr(II) onto the homoionic Ca-montmorillonite under ambient conditions, and the diffuse double layer model-based inverse analysis of sorption data was performed to establish the relevant surface reaction models and obtain corresponding thermodynamic constants. Two types of surface reactions were identified as responsible for the sorption of Cs(I) and Sr(II) onto Ca-montmorillonite: cation exchange at interlayer site and complexation with edge silanol functionality. The thermodynamic sorption modeling provides acceptable representations of the experimental data, and the species distributions calculated using the resulting reaction constants accounts for the predominance of cation exchange mechanism of Cs(I) and Sr(II) under the ambient aqueous conditions. The surface complexation of cationic fission products with silanol group slightly facilitates their sorption at pH > 8.

• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.230-234
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• 2011

In this work, the primary material for a single layered hardmask which can afford a spin-on process was prepared by the minture of organic and inorganic sources. The preparation of hybrid polymer was attempted by esterification from silanol terminated siloxane compounds and acetonide-2,2-bis(methoxy)propionic acid. The optical, thermal and morphological properties of the test hardmask film was examined in terms of cross-linking agent and additives. In addition, the etch rate of hardmask film and photo resist layer were compared. The hybrid polymer prepared from organic and inorganic materials was found to be useful for hardmask film to form the nano-patterns.

• Elastomers and Composites
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• v.48 no.3
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• pp.225-231
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• 2013

In this study, we observed the effect of carboxylated SBR latex and zinc oxide on styrene-butadiene-styrene( SBS) composites for improving abrasion and debris. SBS composite, which added only silica, showed poor mechanical properties, NBS abrasion, and debris, caused by strong filler-filler interaction of silica. In case of adding carboxylated SBR latex, mechanical properties, NBS abrasion and debris of SBS composite were improved. Because of carboxyl group of carboxylated SBR latex interacted with silanol group of silica. Both carboxylated SBR latex and zinc oxide were added, SBS composite showed highest mechanical properties, NBS abrasion, and debris by forming ion cluster between carboxylated SBR latex and zinc oxide. By FT-IR analysis, ion clusters were confirmed that observed zinc carboxylated group stretch peak at $1550{\sim}1650cm^{-1}$ range. SBS composite, SC-4, showed excellent mechanical properties ; tensile strength $156kgf/cm^2$, elongation 936%, tear strength 59.4kgf/cm ; and excellent abrasion characteristics ; NBS abrasion 338%. Also, debris of SC-4 was minimized and showed wave-shape in fracture surface.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.3017-3021
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• 2011

Two chiral stationary phases (CSPs) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 bonded covalently to silica gel were applied for the first time to the resolution of racemic vigabatrin and its analogue ${\gamma}$-amino acids and the resolution results were compared to those on the commercially available Crownpak CR(+) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 coated dynamically onto octadecylsilica gel. While vigabatrin was not resolved at all on Crownpak CR(+), it was resolved quite well on the two CSPs. Among four vigabatrin analogue ${\gamma}$-amino acids, only two were resolved on Crownpak CR(+), but three were resolved on the CSP (CSP 1) containing residual silanol groups and all of four were resolved on the CSP (CSP 2) containing residual silanol group-protecting n-octyl groups. The improved lipophilicity in CSP 2 was proposed to be responsible for its superiority to CSP 1 for the resolution of vigabatrin and analogue ${\gamma}$-amino acids. In addition, the composition of aqueous mobile phase was found to affect the chiral recognition behaviors for the resolution of vigabatrin and analogue ${\gamma}$-amino acids on CSP 2.