29Si CP MAS NMR Research Articles

Trialkoxysilane Grafting in Alcohols: A Simple Approach towards Modified Silica-Based Materials.

The grafting of trialkoxysilanes is the most common method for the surface functionalization of silica gel, and it is usually carried out in the presence of toluene or other solvents such as acetonitrile or acetone. Here, we replaced these solvents with alcohols to afford silica materials containing alkoxy groups linked to the silicon atom. The grafting of N,N-dimethyl-3-amino- or 3-amino-propyltrimethoxysilane was carried out in the presence of several alcohols containing an unsubstituted alkyl chain (C7 and C14), a PEG functionalized chain, or an amino-substituted chain (N,N-dimethylamino, pyridyl). Materials were characterized via solid-state 13C- and 29Si CPMAS NMR and thermogravimetric analysis to prove that alcohols are not "innocent" solvents but take part in the reaction and lead to [RSi(OR1)-(OSi)2] systems where the OR1 group proceeds from the alcohol used in the synthesis. As a proof of concept, we briefly studied the catalytic activity of some of these materials with the aim of showing how different modifications can influence the course of a selected reaction. Finally, a quaternary ammonium salt (QAS)-based silica was prepared containing both an alkyl-QAS and an alkoxy-QAS linked to silicon atoms. This could represent an interesting approach for the development of new antifouling-based materials and, overall, the described strategy could be useful for the preparation of new organosilica materials.

Base-free aqueous Suzuki-Miyaura coupling reaction using recoverable bi-functional Pd supported nanocatalyst

A solid base catalyst comprising pyridine-palladium polyorganosiloxane framework was synthesized via a grafting method. The resulting organic–inorganic hybrid palladium nanomaterial was characterized by 13C CP-MAS NMR, 29Si CP-MAS NMR, XRD, EDX, TEM, TGA, and the BET measurements. The hybrid palladium nanomaterial exhibited high catalytic activity for the Suzuki–Miyaura cross-coupling reaction between aryl chlorides and phenylboronic acid under base-free and aerobic conditions. A maximum turnover number (TON) of 3150, with a 0.2 mol% Pd loading and a reaction temperature of 80 °C in aqueous solution. The catalyst demonstrated remarkable stability, maintaining its activity even after six cycles of reuse without significant loss of activity. TEM images showed that the catalyst retained its structure and high-order mesostructure after several uses. ICP-AES also confirmed the absence of palladium contamination in the final products. Leaching test studies further confirmed the true heterogeneous nature of the developed catalytic system.

Tailoring pore size of mesoporous silica and organosilica using biodegradable pentablock copolymer templates via EISA process

In this work, we have designed unique poly(lactic acid-co-glycolic acid)-b-poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(lactic acid-co-glycolic acid) pentablock copolymers using Pluronic F68 and F108 triblock copolymers as macroinitiators. The poly(lactic acid-co-glycolic acid) (PLGA) blocks were attached as glycolide and lactide monomers at the both ends of each F68 and F108 triblock copolymer. The molecular weights and the block fractions were confirmed by gel permeation chromatography (GPC) and proton nuclear magnetic resonance (1H NMR) for the four kinds of pentablock copolymers. Using these pentablock copolymers as templates, we synthesized mesoporous ethane-silicas as well as silicas by the evaporation-induced self-assembly (EISA) method. 1,2-bis(triethoxysily)ethane (BTEE) were used as an organosilica precursor. The mesoporous ethane-silica samples were characterized using synchrotron small angle X-ray scattering (SAXS), nitrogen sorption experiments, transmission electron microscopy (TEM), and solid-state 29Si CP-MAS NMR. Based on the experimental results, it was confirmed that the porosity and pore diameter can be varied with the PLGA weight fraction of the pentablock copolymer. It is due to the PLGA block in polymer forming the hydrophobic domain in micelles, which leads to the formation of increased pore size over 20 nm without any additive pore expander. In addition, it seems that as the organosilica precursor increases, the association number of block copolymers forming one micelle decreases, resulting in a decrease in pore size. In summary, the polymer template plays a vital part in tuning the structure of the mesoporous ethane-silica samples. Thus, the development of synthetic method of mesoporous organosilica materials using polymer templates with different topology is still challenging and can endow the unique structure and property for mesoporous organosilica for future applications.

Design and synthesis of novel mesostructured nanohybrid materials as antimicrobials

New transparent and monolithic silica hybrid gels with high antibacterial and antifungal activities have been synthesized by soft chemistry. The synthesis has been carried out via sol-gel process, by grafting difunctional-1,3,4-thiadiazole components into a silica network, using 2,4,6,8-tetramethylcyclotetrasiloxane (TMCTS) as a silicon source. The obtained xerogels were characterized using 13C and 29Si CP MAS NMR, FTIR spectroscopy and SEM. The results of this study reveal that the 1,3,4-thiadiazole nuclei have been chemically cross-linked to the silica backbone structure leading to hybrid materials. The pore sizes and specific surface areas were evaluated using N2 adsorption/desorption isotherms. The specific surface area found to be ranged from 302 to 365 m2.g−1. Small particle size with a narrow pore size distribution and an average diameter between 2.5 and 3.5 nm characteristic of a mesoporous structure of xerogels was observed. Scanning electron microscopy showed that the xerogels were formed of spherical nanoparticles whose diameter is of around ten nanometers. Gels antimicrobial activity has been evaluated against Gram-negative and Gram-positive bacteria and the fungus Candida albicans. This study demonstrated significant biosafety of the as-synthesized products and cytocompatibility with normal human skin cells was observed, supporting their potential use as promising candidates for therapeutic application.

Ru(bpy)3]2+-functionalized polydopamine-coated polyurethane foam as an easily reusable macroscopic heterogeneous catalyst for visible-light photocatalysis

An easy-to-handle, highly reusable and efficient [Ru(bpy)3]2+-based heterogeneous photocatalyst was obtained by post-functionalization of a polydopamine-coated open cell polyurethane foam (PDA@PUF) via a silanization process of the mussel-inspired adhesive layer with 3-(triethoxysilyl)propan-1-amine (APTES), followed by an EDC-mediated coupling with [2,2′-bipyridine]-4-carboxylic acid and further complexation with [Ru(bpy)2Cl2] (bpy = 2,2′-bypyridine). The successful covalent grafting of APTES on the PDA layer of PUF and functionalization all over the foam surface with [Ru(bpy)3]2+ was suggested by 29Si CP-MAS NMR, XPS, ICP-AES and SEM-EDX. The macroscopic photocatalyst proved effective in model benzylic amine homocouplings and cross dehydrogenative couplings under visible-light irradiation and molecular oxygen, showing good functional group tolerance and excellent reusability in an easy-to-carry “dip-and-play” mode for at least six runs. Impressively, an improvement of the catalytic performances was even observed in both reactions, which most likely results from a modification of the uppermost layer of polydopamine throughout the successive cycles that renders the photocatalyst more accessible.

Selective capture of palladium(II) from highly acidic solution by proline-valinol amide functionalized silica nanoparticles

With the rapid development of the automobile industry and increasingly strict regulations on automobile exhaust emissions around the world, the production of waste purification catalysts for automobile exhaust will increase, leading to an increasing demand for palladium. Recycling waste three-way catalysts (TWCs) is an important way to obtain palladium resources. However, it is still a challenge to obtain highly selective adsorbents for palladium. Herein, we successfully fabricated two different kinds of Pd2+ selective composite adsorbents (PVA@MSNs and PVA@MONs) through covalent attachment of a proline-valinol amide (PVA) as the ligand on silica nanoparticles. The as-prepared adsorbents were characterized by TEM, SEM, elemental analysis, 29Si and 13C CP MAS NMR, N2-adsorption-desorption isotherm analysis, DLS, zeta-potential, p-XRD and FT-IR, revealing their high loading rate, and the mesoporous structure in the case of PVA@MSNs. In order to evaluate the ability of these two sorbents to selectively capture palladium(II), a series of sequential adsorption experiments were performed. The results showed that 56.35 mg and 67.74 mg of Pd2+ could be captured per gram by PVA@MSNs and PVA@MONs, respectively. Furthermore, they had a stronger selectivity towards Pd2+ than other cations (i.e. Co2+, Ni2+, Zn2+, Pb2+, Fe2+,) present in the simulated sample. Both sorbents were able to remain stable and show consistent performance in cyclic adsorption-desorption runs. Interestingly, the adsorbents realized for the first time the enrichment and recovery of palladium from organic solvents, offering a potential application in palladium catalyst-loaded industrial waste liquid processes.

Sulfonated organosilica-aluminum phosphates as useful catalysts for acid-catalyzed reactions: Insights into the effect of synthesis parameters on the final catalyst

The synthesis, by a sol-gel method, of organosilica-aluminum phosphates, (X)-AlPO(Y)-(Z), using three different silica precursors (X) 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (C), 3-(mercaptopropyl)trimethoxysilane (MPTMS) or Bis[3-(triethoxysilyl)propyl]tetrasulfide (B), with varying Al/P molar ratio (Y = 3–10) and pH of the final gel (Z = 3–9), maintaining an Al/Si= 3 molar ratio, has been carried out. Materials were characterized by XRF, SEM-EDX, XRD, 1H–29Si CP, 27Al and 31P MAS NMR and nitrogen adsorption. The acidity of the solids was evaluated by TGA, XRF and XPS and their catalytic behavior in the etherification of glycerol with tert-butyl alcohol, under microwave irradiation. The solids with an Al/P molar ratio between 3 and 6, synthesized at a pH value over 3 with precursor C, exhibiting the highest values of acidity and predominantly a mesoporous character, showed the best catalytic behavior.

Fenton Stability of Mesoporous Ceria-Silica and Its Role in Enhanced Durability of Poly(arylene ether sulfone) Multiblock Copolymer Composite Membranes for Perfluorosulfonic Acid Alternatives.

To increase the stability of cerium scavengers, we doped cerium oxide on mesoporous silica powders for the application of an oxidative stabilizer. The oxidation–reduction reaction involving hydroxyl radicals (•OH) is investigated with Fenton’s test using eight types of Ce(IV)-mobile compositions of matter 41 (MCM-41) and Ce(III)-MCM-41 powder samples. As confirmed by X-ray photoelectron spectroscopy, the relative amount of Ce3+ inside the mesoporous samples decreases with the increasing time of treatment using the Fenton solution, whereas that of Ce4+ increases. 29Si CP-MAS NMR shows that the condensation of the siloxane bond varies according to the treating time up to 120 h. The mesoporous structure is also analyzed using synchrotron small-angle X-ray scattering and nitrogen adsorption. Further treatment with propane sulfonic acid ensured that the ionic conductivity of the sulfonated mesoporous silica did not decrease. The surface-modified mesoporous silica was incorporated in sulfonated poly(arylene ether sulfone) multiblock membranes. The sulfonated mesoporous silica could overcome the drawbacks of transition metal scavengers, such as a drop in ionic conductivity. Through experiments, we determined that the Ce-doped sulfonated mesoporous silica/sulfonated poly(arylene ether sulfone) composite membranes exhibit high oxidation stability when exposed to hydrogen peroxide and even higher proton conductivity than Nafion at a relative humidity over 60%.

A highly reusable polydimethylsiloxane sorbents for oil/organic solvent clean-up from water

Frequent oil spills in recent years due to human activities including oil drilling, tanker accidents or industrialization, give rise to an urgent need for the development of sorbent materials with high sorption ability, good selectivity and reusability. In this work, PDMS based hydrophobic sorbents acting as oil removing agents were fabricated via bulk polymerization of tetraethyl orthosilicate (TEOS) and different lengths of polydimethylsiloxane (PDMS), without using any activator, initiator, catalyst or solvent. The PDMS sorbents were characterized by using FTIR, 13C and 29Si CPMAS NMR, SEM, contact angle measurements, and thermal gravimetric analysis. The results show the successful preparation of the crosslinked sorbent structure with water contact angle (WCA) of 123°, indicating its hydrophobic structure. The prepared sorbents have high swelling ability in organic liquids/oils in the range of 9–21 g g−1. They have the ability to quickly absorb the oil from the water surface and float before and after oil sorption, while the capacity of the sorbents did not change in different water types. They can be reusable for at least 10 absorption-desorption cycles without capacity change, and have stability in oils over 300 cycles, demonstrating that the obtained hydrophobic PDMS sorbents can be used as oil removing agents in the field of oil spill applications.

An additive-free silicon anode in nanotube morphology as a model lithium ion battery material

Ordered arrays of parallel, cylindrical silicon nanotubes are obtained by aluminothermic reduction of SiO2 nanotubes generated by atomic layer deposition (ALD) on nanoporous aluminum oxide templates. The reduction to amorphous Si (a-Si) is characterized by a combination of X-ray diffraction (XRD), solid-state cross-polarization magic-angle spinning nuclear magnetic resonance (29Si CP-MAS NMR), ultraviolet-visible spectroscopy, attenuated total reflectance infrared spectroscopy (ATR-IR), and X-ray photoelectron spectroscopy (XPS). These a-Si nanotube arrays are electrochemically active in a lithium-ion battery environment when prepared on Cu current collectors without any additives. The absence of the traditional additive carbon black, which is an electrochemically inert conductor, increases the proportion of capacity associated with faradaic reactions (Li incorporation) with respect to the capacitive component. Electrochemical impedance spectroscopy (EIS) and charge-discharge tests demonstrate that the nanotube morphology yields an improved tolerance to fast cycling.

Direct Observation of Carbonate Formation in Partly Hydrated Tricalcium Silicate by Dynamic Nuclear Polarization Enhanced NMR Spectroscopy

Solid-state NMR combined with dynamic nuclear polarization (DNP NMR) is used to study hydration processes in tricalcium silicate (Ca3SiO5, abbreviated as C3S) samples. The studied C3S samples have experienced early stage hydration (1–30 h) and slow aging (9 years) processes. The appearance of Q3 and Q4 lines in the 29Si MAS and 1H → 29Si CP MAS NMR spectra obtained for partly hydrated C3S samples indicated the formation of amorphous silica which corresponds to their carbonation, which was corroborated by complementary FTIR data. Significant DNP signal enhancements obtained for the studied samples allowed to further investigate the C3S carbonation process in detail employing the 1H → 29Si CP MAS FSLG HETCOR technique. Finally, DNP enhanced 1H → 13C CP MAS and 1H → 13C CP MAS FSLG HETCOR techniques enabled to directly observe the formation of carbonate moieties in partly hydrated C3S samples.

Silanization of siliceous materials, part 3: Modification of surface energy and acid-base properties of silica nanoparticles determined by inverse gas chromatography (IGC)

Surface modified silica nanoparticles are well-established composite materials. To improve their embedding and application behavior, surface energy analysis has been performed before and after silanization with mercaptopropyltrimethoxysilane (MPTMS) using inverse gas chromatography technique (IGC). Experiments with two silica materials have been conducted at infinite dilution to determine the dispersive component of the surface energy (γsd) as well as the specific component (γssp) using the van Oss theory and a least-squares procedure evaluating the IGC data of 8 polar probe molecules collectively (instead of evaluating only the data of a pair of monopolar probes as is often the case in IGC studies). After surface silylation, the total surface energy (γst) of pyrogenic silica nanoparticles decreased from 225 mJ/m2 to 149 mJ/m2 referring to both a reduced wettability and an increased hydrophobicity of the MPTMS-modified sample. Moreover, the acidity/basicity parameters according to the van Oss and the Gutmann approach indicated that the acidity of the silica surface decreases by MPTMS grafting. In addition, IGC at finite concentration (using isopropanol as probe molecule) was applied to obtain the energetic heterogeneity of the silica surface. The results showed a bimodal energy distribution with maxima at about 18 and 25 kJ/mol and a reduction of the higher energetic sites from 65% to only 35% after MPTMS treatment. Overall, it can be seen that the dominance of specific interactions on silica surfaces is maintained even after extensive silanization. These findings are in agreement with the results of 29Si CP MAS NMR measurements which confirm the assignment of higher energetic sites to silanol groups. For the interpretation of the IGC results, quantum chemical calculations proved the preferred interaction of isopropanol onto silica surfaces via hydrogen bridging.

Biomass waste rice husk derived silica supported palladium nanoparticles: an efficient catalyst for Suzuki–Miyaura and Heck–Mizoroki cross-coupling reactions

Here, we report an inexpensive, versatile, and environmentally benign biomass waste rice husk derived amorphous silica-supported palladium (PdNPs/RH-SiO2) nano-catalyst for Suzuki–Miyaura and Heck–Mizoroki cross-coupling reactions. The proposed catalyst was prepared in two steps. In the first step, amorphous SiO2 obtained by calcination of rice husk and the following deposition of palladium nanoparticles by using the chemical reduction method in the second step. The physico-chemical properties of the catalysts were investigated by N2 adsorption–desorption, XRD, XPS, 29Si CP-MAS NMR, and TEM analysis. The palladium content in the catalysts has been determined by ICP-OES analysis. The 1% PdNPs/RH-SiO2 exhibited excellent catalytic performance for Suzuki–Miyaura and Heck–Mizoroki C–C cross-coupling reactions to produce biaryl and stilbene compounds with >99% selectivity and excellent TON values (529 and 524). Furthermore, the catalyst is repeatedly used for four consecutive cycles without a significant drop in the yield.

Effect of aluminum and sodium on the sorption of water and methanol in microporous MFI-type zeolites and mesoporous SBA-15 materials

The interaction and nature of surface sites for water and methanol sorption on MFI-type zeolites and mesoporous SBA-15 were investigated by solid-state NMR spectroscopy and correlated with the desorption enthalpies determined via TGA/DSC. For siliceous Silicalite-1, 29Si CPMAS NMR studies support stronger methanol than water interactions with SiOH groups of Q3-type. On siliceous SBA-15, SiOH groups of Q2-type are accompanied by an enhanced hydrophilicity. In aluminum-containing Na-ZSM-5, Na+ cations are strong adsorption sites for water and methanol as evidenced by 23Na MAS NMR in agreement with high desorption enthalpies of ΔH = 66–74 kJ/mol. Solid-state NMR of aluminum-containing Na-[Al]SBA-15, in contrast, has shown negligible water and methanol interactions with sodium and aluminum. Desorption enthalpies of ΔH = 44–60 kJ/mol hint at adsorption sites consisting of SiOH groups influenced by distant framework aluminum. On H-ZSM-5, Brønsted acidic OH groups are strong adsorption sites as indicated by partial protonation of water and methanol causing low-field shifts of their 1H MAS NMR signals and enhanced desorption enthalpies. Due to the small number of Brønsted acid sites in aluminum-containing H-[Al]SBA-15, water and methanol adsorption on this material is suggested to mainly occur at SiOH groups with distant framework aluminum species, as in the case of Na-[Al]SBA-15.

Synthesis, charaterization and optical properties of nanostructured silica hybrid materials obtained by soft chemistry from perhydropolysilazane/1,2,4-triazole precursors

Nanostructured silica hybrid materials have been synthesized via soft chemistry way, by the incorporation of functional 1,2,4-triazole components into a silica network, using a perhydropolysilazane (PHPS) as a silica source and 1,2,4-triazole components as templates. The compositions, morphological and textural properties of the as-synthesized samples have been studied by 13C and 29Si CP MAS NMR, FTIR and SEM. The spectroscopy results suggest that the organic moieties have been chemically linked to the silica skeleton leading to hybrid materials in which Si–N, Si–O and Si–S bridges are created. Nitrogen adsorption-desorption analysis (BET) shows that the surface area varied between 385 and 425 m2 g−1. The 29Si CP-MAS NMR displays signals between -70 and -120 ppm corresponding to Q2, Q3 and Q4 units. The optical properties have been studied also by UV–visible diffuse reflection spectroscopy and photoluminescence (PL). This study reveals that the direct gap energies varied between 0.71 and 2.53 eV. Photoluminescence shows that the silica nanohybrids are suitable to the emission of blue light with wavelength (λem) values of about 470-480 nm. The PL emission results also from some silicon/oxygen-related defect species.

Preparation and characterization of novel bi-functionalized xerogel for removal of methylene blue and lead ions from aqueous solution in batch and fixed-bed modes: RSM optimization, kinetic and equilibrium studies

A new bi-functionalized xerogel is fabricated and then was identified by 29Si CP MAS NMR, SEM, FTIR, and nitrogen adsorption–desorption approaches. As-prepared xerogel efficiency for simultaneous uptake of methylene blue (MB) and Pb2+ ions from aqueous solution is investigated. Individual and combination effects of operating variables (xerogel mass, contact time and initial MB and Pb2+ ion concentration) on the retention performance is achieved with central composite design (CCD) and upgraded through response surface method (RSM). Batch equilibrium outcomes uncovered that MB and Pb2+ ions adsorption onto hybrid composite could be all around depicted by Langmuir isotherm model contrasted with Freundlich equation. Howbeit, the column trials reported that the breakthrough capacities of MB and Pb(II) are observed to be 512 mg.g−1 and 400 mg.g−1 respectively. XPS and FTIR investigations uncovered that the main mechanism of lead uptake ought to be credited to the chelation with –NH2 and ion exchange with –SH groups in the xerogel frameworks. While the MB adsorption system is proposed to be electrostatic attractions, π-π stacking interactions and hydrogen bonds. The work undertaken in this research highlights the major role of the as-synthesized xerogel for treatment of industrial wastewater.

Surface modification of aqueous miscible organic layered double hydroxides (AMO-LDHs).

Silane modification of layered double hydroxides (LDHs) plays an important role in controlling the surface hydrophobicity and improving the compatibility of LDHs dispersed in non-polar materials. However, the surface modification of conventional LDHs in hydrous conditions typically results in aggregated particle morphologies, low surface areas and accessible pore volumes. In this study, well dispersed and high surface area silane grafted AMO-Zn2MgAl-CO3 LDH were prepared using the silane coupling agents (triethoxyvinylsilane (TEVS), triethoxyoctylsilane (TEOS) and (3-glycidyloxypropyl)trimethoxysilane (TMGPS)) in anhydrous acetone. Solution 1H NMR spectroscopy was initially used to study the rate and extent of silane reactivity with AMO-Zn2MgAl-CO3 LDH. Powder XRD, TEM, N2 BET specific surface area and total pore volume measurements showed that the structure and morphology of silane-treated AMO-Zn2MgAl-CO3 LDHs remained largely unchanged. Solid state 13C CP-MAS, 27Al DP-MAS and 29Si CP-MAS NMR spectroscopy indicates that the silanes have been successfully grafted onto the surface of the LDH. In addition to maintaining their structure, morphology, high surface area and total pore volume, these surface-functionalised LDHs are now more hydrophobic, displaying a saturation water vapour uptake (<4 wt%) that is ca. 60% lower than the untreated AMO-LDH.

Structure and electrochemical properties of highly conductive and porous carbon nanofiber derived from inclusion complex of cyclodextrin-phenylsilane

A new type of PAN/phenylsilane-based CNF (PPSCD) composite with inclusion complex (IC) is prepared by one-step electrospinning for high-performance electrode materials for supercapacitors. All three cyclodextrin phases (α-CD, β-CD and γ-CD) exhibit different capabilities for the formation of ICs that depend on the size/shape match and binding force between the host CD cavity and the guest molecule of phenylsilane (PS). The effect of the stronger binding and greater interaction of PS in the cavity of α-CD on the morphology and structural properties of the electrospun CNFs are investigated by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and 29Si CP-MAS NMR. The inclusion of small PS molecules is more selective in α-CD, possibly due to stronger binding and greater interaction of PS in the cavity as compared to β- and γ-CD. The PPSα-CD electrode demonstrates superior specific capacitance (173 Fg−1 at a current density of 1 mAcm−2) and high energy density (22.0–8.0 Whkg−1 at power densities ranging from 400 to 10,000 Wk−1) in an aqueous solution. Therefore, the highly conductive PPSα-CD composite provides efficient transport of electrolyte ions and low resistance for charge diffusion in the electrolyte, thereby yielding good capacitive behavior.

Multifunctional periodic mesoporous benzene-silicas for evaluation of CO2 adsorption at standard temperature and pressure

Abstract Bi-functional periodic mesoporous organosilicas (PMOs) embedded with phenylene- and isocyanurate-bridging groups have been synthesized by a one-pot co-condensation method using 1,4-bis(triethoxysilyl)benzene and tris[3-(trimethoxysilyl)propyl]isocyanurate precursors in the presence of a poly(ethylene oxide)-poly( dl -lactic acid-co-glycolic acid)-poly(ethylene oxide) (PEO-PLGA-PEO) triblock copolymer named LGE54 under acidic conditions. Block copolymer template has been removed by solvent-extraction to get the template-free PMO whereas PLGA block chains from the copolymer template were also removed selectively by thermal treatment at 250 °C retaining PEO chains inside the silica framework. Furthermore, the bi-functional PMO and tri-functional PEO containing PMOs were modified with N-[3-(trimethoxysilyl)propyl]ethylenediamine to prepare amine-coated PMOs on the pore surface. The bi-, tri-, and tetra-functional PMO samples have been thoroughly characterized using small angle X-ray scattering (SAXS) and nitrogen adsorption isotherms to resolve the presence of ordered mesostructure and surface area of the PMOs. Also, solid-state 13C- and 29Si CP-MAS NMR studies have been performed to investigate significant chemical linkages from amine-containing modifiers and poly(ethylene oxide) group inside and on the surface of PMO samples. Scanning electron microscopic (SEM), elemental analysis, and thermogravimetric analysis (TGA) have been carried out to obtain the morphology, elemental percentage and thermal stability of the multi-functional PMO samples, respectively. CO2 capture has been investigated on multi-functional PMO samples at 25 °C and 1 atm using a mixed flow by 3:2 vol ratio of CO2 and N2 gas. Amine-functionalized PMO has shown significantly higher amount of CO2 uptake than those obtained using PMO itself and the respective PMOs modified with different functionalities.

3-Arm PEG Based Amphiphilic Polymer Sorbents for Polar and Non-Polar Liquids

Crosslinked polymer gels are gaining technological and industrial attention due to their sophisticated application features. Herein, a highly effective amphiphilic polymeric network capable of absorbing polar and nonpolar solvents was produced using hydrophilic glycerol ethoxylate, a member of star type polyethylene glycol (s-PEG), and different hydrophobic organosilane monomers by bulk polymerization as utilized under an inert atmosphere. In this context, the preparation of amphiphilic polymeric networks was achieved by the reaction between hydroxyl terminated s-PEG and ethoxysilane terminated organosilane without using any initiator, activator or a catalyst. SEM, FTIR, 13C and 29Si CPMAS NMR and TGA are used for morphological, structural and thermal characterization of the prepared materials. Likewise, the absorption behavior of amphiphilic polymeric networks was determined by measuring their swelling ratios in polar and nonpolar solvents. Because of having a hydrophobic and hydrophilic structure in their 3D polymeric structure, the obtained polymeric networks behave as an organogel in oil medium, while they can prepared as a hydrogel in aqueous medium. The effect of crosslinker’s difference on the swelling capacity of sorbent were researched by comparing different molecular weight of monomers, and it was found that the molecular structure of organosilane monomers had significant influence on the swelling ability of obtained amphiphilic sorbents. By the use of easy preparations, not needing extra agents for the synthesis, having high and quick absorption abilities in organic solvents showed that the resulting amphiphilic sorbent have potential as absorbents for different organic solvents. Also, the degradable features of amphiphilic polymer networks in water open up optimum application opportunities for additional uses, such as with drug delivery agents.