Silanol Functionalities Research Articles

Preparation of Fe-Modified Diatomite-Based Ceramsite for Efficient Phosphate Adsorption: Utilizing Diatomite’s Distinctive Porous Structure and Surface Silanol Groups

Ceramsites are extensively employed as substrates for adsorbents in studies focused on phosphorus adsorption, leaving ceramsites crafted from diatomite less explored. Diatomite-based ceramsite, with its distinct porous architecture and surface silanol functionalities, is adept at supporting a variety of metal oxides, presenting a distinct advantage over other ceramsite variants. In light of this, the present study embarked on producing diatomite-based ceramsite using diatomite as the foundational material, subsequently enhancing it through the incorporation of Fe, thus yielding an Fe-modified diatomite-based ceramsite. Through adsorption testing, the modified ceramsite demonstrated a significantly improved adsorption capacity of 4.06 mg P/g, marking a substantial enhancement from the initial capacity of 0.9 mg P/g. The process of phosphorus adsorption exhibited a strong alignment with the Langmuir isotherm model and the pseudo-second-order kinetic model. In-depth analyses employing XRD, FTIR, zeta potential, and XPS techniques have revealed that the principal mechanisms driving the adsorption process are centered on interactions involving electrostatic forces, the formation of chemical precipitates, and the exchange of ligands. This investigation not only opens new avenues for the application of diatomite-based ceramsite but also lays down a theoretical foundation for its modification, thereby enriching the spectrum of its utility.

Synthesis of large mesoporous silica for efficient CO2 adsorption using coal gasification fine slag

Coal gasification fine slag (CGFS), a byproduct of the coal gasification process, is currently being recognized as a resource with significant potential for value addition and sustainable applications, especially in synthesizing CO2 adsorbents. The overarching challenges in this domain include the attainment of high-efficiency, environmentally benign transformation of CGFS into useful products, and the development of cost-effective adsorbent materials featuring precisely engineered pore structures. In this study, a hierarchical porous nanostructured silica material is synthesized rapidly, efficiently, and cost-effectively through acid leaching and alkaline dissolution-assisted hydrothermal treatment, employing CGFS as the precursor. The mass ratios of sodium hydroxide (NaOH) to CGFS range from 0.4 to 1, resulting in varying morphologies and adsorption properties. Specifically, the sample with the NaOH to CGFS ratio of 0.6 (CGFS-0.6) shows the best adsorption performance. The adsorption capacities are 2.87 mmol/g and 8.49 mmol/g at 20 °C with 15 % and 45 % CO2 concentration, respectively. The material is characterized by a well-developed pore structure shaped like a bouquet of flowers, with a specific surface area of 457 m2/g and pore volume reaching 2.34 cm3/g. During the hydrothermal processing, silicate/aluminosilicate entities self-organized into a Si-O-Na/Al network structure, endowing the synthesized adsorbent with optimal internal porosity and silanol functionalities. The adsorption equilibrium is achieved rapidly within 10 min, and CO2 adsorption stability remains robust across 20 successive cycles. All isothermal models of the adsorbents conform to the Sips model. This study offers a promising pathway for the value-enhanced utilization of coal-derived solid wastes.

Electrokinetic characterization of hybrid NOA 81-glass microchips: Application to protein microchip electrophoresis with indirect fluorescence detection.

A low-cost and straightforward hybrid NOA (Norland optical adhesive) 81-glass microchip electrophoresis device was designed and developed for protein separation using indirect fluorescence detection. This new microchip was first characterized in terms of surface charge density via electroosmotic mobility measurement and stability over time. A systematic determination of the electroosmotic mobility (μeo ) over a wide pH range (2-10) and at various ionic strengths (20-50mM) was developed for the first time via the neutral marker approach in an original simple frontal methodology. The evolution of μeo was proved consistent with the silanol and thiol functions arising from the glass and the NOA materials, respectively. The repeatability and reproducibility of the measurements on different microchips (RSD<14%) and within 15 days (less than 5% decrease) were successfully demonstrated. The microchip was then applied for the efficient electrophoretic separation of proteins in a zonal mode coupled with indirect fluorescence detection, which is, to our knowledge, the first proof of concept of capillary zone electrophoresis in this hybrid microsystem.

Synthesized graphene oxide and fumed aerosil 380 dispersion stability and characterization with partially hydrolyzed polyacrylamide

Hydrolyzed polyacrylamide (HPAM) is a commonly used polymer for the chemicals, mining and refining processes of hydrocarbon but suffers from a persistent high-temperature instability problem. In contrast, the nanoparticle suspension remains a technical challenge because of the strong interactions of van der Waal forces within nanoparticles, which always encourage aggregation. This research sought to improve nanoparticles (NP) stability and polymer (HPAM) rheological properties to improved hydrocarbon recovery by utilizing synthesized graphene oxide (GO) nanosheets and fumed Aerosil 380 Silica oxide (SiO2). The aqueous nanocomposites based on HPAM-GO and HPAM-SiO2 in aqueous polymeric solutions have been developed, and its viscoelastic and static behaviour is studied. The results imply that by adding fumed silica NP, the viscoelastic behaviour of HPAM is marginally improved, particularly in high temperatures and salinity, however, the inclusion of GO's significantly improves the viscosity and stability of the base polymer fluid at high temperatures. The Fourier data for the transformation of the infrared spectrum confirmed that the hydrogen bonding formed between HPAM carbonyl groups and silica NP surface silanol functionality and covalent interlinking of electrostatic h-bonding between HPAM and functional GO contributed to the improved stabilization and improved rheological performance that helps to recover high salinity and temperature hydrocarbons.

Superhydrophobic and Compressible Silica-polyHIPE Covalently Bonded Porous Networks via Emulsion Templating for Oil Spill Cleanup and Recovery

We synthesize porous polyHIPE networks with silanol functionalities in the polyHIPE backbone. These silanol functionalities are used for covalent bonding with silica aerogels embedded in the polyHIPE. Covalent bonding between silica and polyHIPE networks are confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy. Silica aerogels covalently bonded with polyHIPE network show macroporous and mesoporous morphologies and possess excellent properties like high bendability, high elasticity, superhydrophobicity (~160°), low density (~0.128 g/cm3), and low thermal conductivity (~0.045 W/m·K). Oil absorption from water/oil mixtures and recovery of the absorbed oil (by squeezing) from flexible silica-polyHIPE networks is studied. The silica-polyHIPE is shown to absorb crude oil ~16-times its own weight and can be reused multiple times after recovery. Hence, such materials are very important for oil spill cleanup applications from aqueous systems.

Separation of asymmetrically capped double-decker silsesquioxanes mixtures

A synthetic path to asymmetric side-capped double-decker shaped silsesquioxanes (DDSQ) and subsequent isolation is described. By strategically using a combination of dichloro and trichlorosilane capping agents, a resultant product with mixed silanol functionalities was obtained. The use of preparatory liquid chromatography (LC) cleanly separated DDSQ compound with asymmetric functionality, and HPLC provided a quantitative technique to analyze mixture ratios. These mixture ratios did not follow the expected statistical trend due to the steric effects on the rate of capping. As a consequence, a decreased amount of the desired asymmetric DDSQ was observed in some cases. This was overcome by varying the ratio of capping agents. Overall, this work demonstrates access to asymmetric DDSQ cages is feasible, and LC is an effective separation technique.

Investigation of simultaneous adsorption properties of Cd, Cu, Pb and Zn by pristine rice husks using ICP-AES and LA-ICP-MS analysis

Rice husks are an agricultural waste product that has unique metal adsorption capabilities to remediate heavy metal contaminated sites. It is insoluble in water, has strong chemical stability and mechanical strength with a high silica content (~20%), and possesses a high surface area with granular structure for adsorption that is rich with cation exchanging silanol (SiOH) functionalities. The purpose of this study is to determine the adsorption capabilities of pristine rice husks (PRH) for practical field applications. Sorption experiments were performed to evaluate simultaneous Cd, Cu, Pb, and Zn sorption by rice husk at varying pH, concentration, reaction temperature, and maximum adsorption capability using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Optimum adsorbent mass of 1.0g of husk was determined by using increasing amounts of PRH (0.1–2.0g) with 10ppm concentration of Cd, Cu, Pb, and Zn at environmentally relevant pH6.92. The resulting percent Cd, Cu, Pb and Zn removal efficiency (%R) order by 1. 0g of PRH was highest for Pb and lowest for Zn under competitive equilibration conditions. Isotherm model plots of Cd, Pb, and Zn adsorption follows better with the Freundlich model than Langmuir model. Copper and Zn adsorption is endothermic while Cd and Pb adsorption process is exothermic. Spatial elemental distribution plots obtained by LA-ICP-MS on the PRH visually demonstrate metals are adsorbed on the silica rich areas of the rice husk. The ability to successfully sequester Cd, Cu, Fe, Pb and Zn in contaminated soils and acid mine water was demonstrated. Due to its abundance as an agricultural waste and its low cost it is clear that untreated raw rice husk has a great potential as a sustainable metal sequestering medium for metal contaminated acid mine water and soils.

Rheological Properties of Partially Hydrolyzed Polyacrylamide Seeded by Nanoparticles

This work aims to improve the rheological properties of partially hydrolyzed polyacrylamide (HPAM) for enhanced oil recovery by using silica (or silicon dioxide, SiO2) nanoparticles (NPs). Novel aqueous HPAM-based SiO2 nanocomposites were formulated, and their rheological properties were investigated under different salinities, temperatures, and aging times. The results show that the inclusion of silica NPs significantly improved the viscosity and viscoelastic properties of HPAM especially under high temperature and high salinities. The NP/HPAM hybrid showed an impressive thermal stability at T = 80 °C after 12 days, and the viscosity reached ∼5 times that of HPAM at 0.8 wt % NP loading. The Fourier transform infrared spectral data confirmed that the formation of a hydrogen bond between the carbonyl groups in HPAM and the silanol functionalities on the surface of silica NPs contributed to the improved performance. The oscillation test indicated that seeding SiO2 remarkably facilitated the cross-links amon...

Fire behaviour and morphology of epoxy matrices designed for composite materials processed by infusion

The present work is about the investigation of the fire behavior of epoxy networks designed for structural composite materials used in aeronautics. Two high-Tg, infusion-suitable epoxy systems were studied. A model system was based on tetraglycidyl(diaminodiphenyl)methane (TGDDM) as an epoxy prepolymer, and 4,4′ methylene bis(2,6-diethylaniline) (MDEA) as a curing agent. A second system was based on a commercial aeronautic formulation specially designed for the infusion process. The triSilanolPhenyl POSS (POSSOH) was chosen as an additive due to the presence of phenyl groups and silanol functions that could possibly react with the network compounds. In this perspective, an aluminium salt (aluminium tri(acetylacetonate)) was introduced in presence of POSSOH in order to enhance the reaction of the additive with the epoxy monomer. The study of the morphology revealed intricate structures, with an overall good dispersion of the POSSOH in the epoxy networks. In terms of fire behaviour, same tendencies were observed for both epoxy networks, i.e. the combined presence of POSSOH and the aluminium-based additive brought significant improvements with a substantial and effective intumescent-like behaviour.

A Surface Tailoring Method of Ultrathin Polymer Gate Dielectrics for Organic Transistors: Improved Device Performance and the Thermal Stability Thereof

Tailoring the surface of the dielectric layer is of critical importance to form a good interface with the following channel layer for organic thin film transistors (OTFTs). Here, a simple surface treatment method is applied onto an ultrathin (&lt;15 nm) organosilicon‐based dielectric layer via the initiated chemical vapor deposition (iCVD) to make it compatible with organic semiconductors without degrading its insulating property. A molecular‐thin oxide capping layer is formed on a 15 nm thick poly(1,3,5‐trimetyl‐1,3,5‐trivinyl cyclotrisiloxane) (pV3D3) by a brief oxygen plasma treatment. The capping layer greatly enhances the thermal stability of the dielectrics, without degrading the original mechanical flexibility and insulating performance of the dielectrics. Moreover, the surface silanol functionalities formed by the plasma treatment can also be utilized for the surface modification with silane compounds. The surface‐modified dielectrics are applied to fabricate low‐voltage operating (&lt;5 V) pentacene‐based OTFTs. The highest field‐effect mobility of the device with the surface‐treated 15 nm thick pV3D3 is 0.59 cm2 V−1 s−1, which is improved up to two times compared to the TFT with the pristine pV3D3. It is believed that the simple surface treatment method can widely extend the applicability of the highly robust, ultrathin, and flexible pV3D3 gate dielectrics to design the surface of the dielectrics to match well various kinds of organic semiconductors.

Polymer sol-gel composite inverse opal structures.

We report on the formation of composite inverse opal structures where the matrix used to form the inverse opal contains both silica, formed using sol-gel chemistry, and poly(ethylene glycol), PEG. We find that the morphology of the inverse opal structure depends on both the amount of PEG incorporated into the matrix and its molecular weight. The extent of organization in the inverse opal structure, which is characterized by scanning electron microscopy and optical reflectance data, is mediated by the chemical bonding interactions between the silica and PEG constituents in the hybrid matrix. Both polymer chain terminus Si-O-C bonding and hydrogen bonding between the polymer backbone oxygens and silanol functionalities can contribute, with the polymer mediating the extent to which Si-O-Si bonds can form within the silica regions of the matrix due to hydrogen-bonding interactions.

Surface-initiated hyperbranched polyglycerol as an ultralow-fouling coating on glass, silicon, and porous silicon substrates.

Anionic ring-opening polymerization of glycidol was initiated from activated glass, silicon, and porous silicon substrates to yield thin, ultralow-fouling hyperbranched polyglycerol (HPG) graft polymer coatings. Substrates were activated by deprotonation of surface-bound silanol functionalities. HPG polymerization was initiated upon the addition of freshly distilled glycidol to yield films in the nanometer thickness range. X-ray photoelectron spectroscopy, contact angle measurements, and ellipsometry were used to characterize the resulting coatings. The antifouling properties of HPG-coated surfaces were evaluated in terms of protein adsorption and the attachment of mammalian cells. The adsorption of bovine serum albumin and collagen type I was found to be reduced by as much as 97 and 91%, respectively, in comparison to untreated surfaces. Human glioblastoma and mouse fibroblast attachment was reduced by 99 and 98%, respectively. HPG-grafted substrates outperformed polyethylene glycol (PEG) grafted substrates of comparable thickness under the same incubation conditions. Our results demonstrate the effectiveness of antifouling HPG graft polymer coatings on a selected range of substrate materials and open the door for their use in biomedical applications.

Enhancing rheological properties of hydrophobically associative polyacrylamide aqueous solutions by hybriding with silica nanoparticles

ABSTRACTOrganic/inorganic hybrid aqueous solutions were prepared by mixing silica nanoparticle suspension and hydrophobically associating polyacrylamide (HAPAM) solution, and their rheological behaviors were examined in both pure water and brine in comparison with HAPAM. It was found that HAPAM/silica hybrid exhibits viscosity enhancement in aqueous solution and better heat‐ and salt‐ tolerances than HAPAM. Meanwhile, their long‐term thermal stability is also improved. Cryo‐TEM observation reveals that a reinforced three‐dimensional network structure of HAPAM/silica hybrid is formed. These improved properties are attributed to the formed hydrogen bond between carbonyl groups in HAPAM skeleton and silanol functionalities in silica nanoparticles in the hybrid system, and the silica nanoparticles in the hybrid act as physical crosslinkers between macromolecules. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40876.

Functionalization of PDMS modified and plasma activated two-component polyurethane coatings by surface attachment of enzymes

This article describes a new strategy for coupling the enzyme horseradish peroxidase to a two-component polyurethane (2C-PUR) coating. A stable polymer conjugate was achieved by combining the enzyme and the 2C-PUR coating which was modified with poly(dimethylsiloxane) (PDMS), located at the surface. An atmospheric pressure plasma jet system was used to convert alkyl groups from the PDMS into polar silanol functionalities. This conversion was proven by X-ray photoelectron spectroscopy and dynamic contact angle measurements. In addition, the stability of the activated 2C-PUR surface containing silanol groups was determined by measuring the contact angle as a function of time. Compared to the non-modified 2C-PUR systems the one with PDMS displayed a higher stability over a time period over 28h. In a silanization process the coating was treated with (3-aminopropyl) trimethoxysilane and the enzyme was subsequently immobilized to the coating via the cross linker glutaraldehyde to receive new biomimetic catalytic/enzymatic functions. The chemical immobilization (chemisorption) of the enzyme to the surface showed statistically significant higher biological activity as compared to references samples without using a cross linker (physisorption). The presented technique offers the opportunity to design new and smart multifunctional surface coatings which employ biomimetic capabilities.

Self-assembled structure formation from interactions between polyhedral oligomeric silsesquioxane and sorbitol in preparation of polymer compounds

This study investigated the factors responsible for molecular interactions leading to self-assembly between the molecules of sorbitol and polyhedral oligomeric silsesquioxane (POSS) carrying organic and inorganic side groups. The study also assessed the utility of such molecular adducts as processing aids which will aid preparation of polymer compounds, films, and spun fibers. Several POSS molecules containing silanol functionalities and alkyl and phenyl substituents were used to separately evaluate the effects of hydrogen bonding and π−π interactions on formation of molecular adducts. The molecular adducts were studied using differential scanning calorimetry, wide angle X-ray diffraction, scanning electron microscopy, mass spectrometry, oscillatory shear rheology, and molecular dynamics simulation. The study revealed that POSS-sorbitol self-assembled structures were formed only when hydrogen bonding and π−π interactions worked cooperatively. In addition, self-assembled molecules were of amorphous nature although POSS and sorbitol were crystalline.

Exploiting POSS–Sorbitol Interactions: Issues of Reinforcement of Isotactic Polypropylene Spun Fibers

This study investigates the issues involving reinforcement of isotactic polypropylene (iPP) spun fibers by molecular adducts originating from the synergistic interactions of polyhedral oligomeric silsesquioxane (POSS) containing silanol functionalities (silanol–POSS) and di(benzylidene)sorbitol (DBS). The molecular adducts of silanol–POSS and DBS were low viscosity liquids at fiber spinning temperature, turned into cylindrical domains during fiber spinning, and remained as nanoparticles in the fibers. The fibers were analyzed by differential scanning calorimetry, wide-angle X-ray diffraction , scanning electron microscopy, and transmission electron microscopy. It was observed that iPP compounds with 2–5 wt % silanol–POSS and 1 wt % DBS could be spun into fibers with close to 40% reduction in diameter compared to unfilled iPP. These fibers offered 60–80% increase in tensile modulus, 50–60% increase in tensile strength, and 100% increase in yield strength compared to unfilled iPP. The silanol–POSS particles...

Cyclic tetravinylsiloxanetetraols as hybrid inorganic–organic thiol-ene networks

In this work, organic-inorganic hybrid materials containing stable silanol functionalities were designed by incorporating cyclic tetravinylsiloxanetetraols into photopolymerized polymer networks via the thiol-ene reaction, with the intent of tailoring the thermal and mechanical properties of the resulting materials. The effects of the cyclic tetravinylsiloxanetetraols concentration on the thermomechanical properties and thermal stability of pentaerythritol triallyl ether/pentaerythritol tetra(3-mercaptopropionate) (APE-PETMP) and allyl isocyanurate/pentaerythritol tetra(3-mercaptopropionate) (TTT-PETMP) ternary networks were evaluated using dynamic thermomechanical analysis and thermogravimetric analysis, respectively. Photopolymerization kinetics were monitored using real-time FTIR. Interestingly, an increase in glass transition temperature was observed with the APE-PETMP networks while a decrease in glass transition temperature was observed for the TTT-PETMP networks with increasing concentration of [Vi(OH)SiO]4. These observations are discussed in terms of cross-link density and monomer rigidity.

Silica nanoparticle covered with mixed polymer brushes as Janus particles at water/oil interface

Silica nanoparticles (NSiO2) are modified with mixed polymer brushes derived from a block copolymer precursor, poly(methyl methacrylate)-b-poly(glycidyl methacrylate)-b-poly(tert-butyl methacrylate) with short middle segment of PGMA, through one step “grafting-onto” approach. The block polymer precursors are prepared via reversible addition–fragmentation chain transfer-based polymerization of methyl methacrylate, glycidyl methacrylate, and tert-butyl methacrylate. The grafting is achieved by the reaction of epoxy group in short PGMA segment with silanol functionality of silica. After hydrolysis of poly(tert-butyl methacrylate) segment, amphiphilic NSiO2 with “V-shaped” polymer brushes possessing exact 1:1 molar ratio of different arms were prepared. The functionalized particles self-assemble at oil/water interfaces to form stable large droplets with average diameter ranging from 0.15 ± 0.06 to 2.6 ± 0.75 mm. The amphiphilicity of the particles can be finely tuned by changing the relative lengths of poly(methyl methacrylate) and poly(methacrylic acid) segments, resulting in different assembly behavior. The method may serve as a general way to control the surface property of the particles.

Sorbitol–POSS Interactions on Development of Isotactic Polypropylene Composites

This study investigates the nature of interactions between the molecules of polyhedral oligomeric silsesquioxane (POSS) containing silanol functionalities (silanol–POSS) and di(benzylidene)sorbitol (DBS) encountered in the development of nanocomposite fibers from the compounds of POSS, DBS, and isotactic polypropylene (iPP). The interactions were investigated using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and oscillatory shear rheology. Mass and NMR spectrometry revealed that the molecules of silanol–POSS and DBS formed several amorphous noncovalent molecular complexes promoted by hydrogen bonding. More abundant complex formation was observed with silanol–POSS molecules carrying four silanol groups and phenyl substitutions. Such complex formation deterred fibrillation of DBS when the compounds of iPP, DBS, and silanol–POSS were cooled from homogeneous melt ...

State of water molecules and silanol groups in opal minerals: a near infrared spectroscopic study of opals from Slovakia

Recently, near infrared spectroscopy in combination with double derivative technique has been effectively used by Christy (Vib Spectrosc 54:42–49, 2010) to study and differentiate between free and hydrogen bonded silanol groups on silica gel surface. The method has given some insight into the type of functionalities, their location in silica gel samples, and the way the water molecules bind onto the silanol groups. The important information in this respect comes from the overtones of the OH groups of water molecules hydrogen-bonded to free silanol groups, and hydrogen-bonded silanol groups absorbing in the region 5,500–5,100 cm−1. Chemically, opal minerals are hydrated silica and the same approach was adapted to study the state of water molecules, silanol functionalities, and their locations in opal samples from Slovakia. Twenty opal samples classified into CT and A classes and one quartz sample were used in this work. The samples were crushed using a hydraulic press and powderized. Each sample was then subjected to evacuation process to remove surface-adsorbed water at 200°C, and the near infrared spectrum of each sample was measured using a Perkin Elmer NTS FT-NIR spectrometer equipped with a transflectance accessory and a DTGS detector. The samples were also heated to 750°C to remove the hydrogen-bonded silanol groups on the surface to reveal their locality. Second derivative profiles of the near infrared reflectance spectra were obtained using the instrument’s software and used in the detailed analysis of the samples. The analysis of the near infrared spectra and their second derivative profiles had the aim in finding relationships between the surface chemical structure and the classification of opal samples. The dry opal samples were also tested for their surface adsorption effectivity toward water molecules. The results indicate that the opal samples contain (1) surface-adsorbed water, (2) free and hydrogen-bonded silanol groups on the surface, (3) trapped water molecules in the bulk, and (4) free and hydrogen-bonded silanol groups in the cavity surfaces in the bulk. A part of the water molecules in the bulk of opal minerals are found as free molecules and the rest are found in hydrogen-bonded state to either free or vicinal or geminal silanol groups.