Siloxane Functional Groups Research Articles

Enhancing stability and performance of graphene oxide membrane grafted on low-cost rich-silica support: A comparative study of two activation approaches

Although graphene oxide has shown encouraging results in membrane field, it has a major stability issue when coated on ceramic supports, particularly those formed of geomaterials. This work aims to prepare stable graphene oxide layer deposited on a low-cost rich-silica support. The graphene oxide membrane was prepared using grafting method, which included surface activation and modification followed by the graphene oxide layer coating. Siloxane functional groups were activated using either hydrochloric acid or piranha solution to determine which of them provided the highest membrane stability. The support surface was chemically modified using 3-glycidoxypropyltrimethoxysilan followed by the deposition of graphene oxide nanosheets using evaporation-assisted assembly. According to Fourier-transform infrared spectroscopy, the support activated with piranha solution has more silanol functional groups than the support activated with hydrochloric acid while the appearance of 3-glycidoxypropyltrimethoxysilan band on the modified support, proves the accomplishment of grafting. The stability test of the membrane demonstrated a highly stable deposited layer for the graphene oxide membrane activated with piranha solution in different pH contrary to the non-grafted graphene oxide membrane and the graphene oxide membrane activated with hydrochloric acid that peeled off from the support. On the support activated with piranha solution, 3-glycidoxypropyltrimethoxysilan concentration was investigated and an optimal value of 0.1 mol L−1 was determined. The filtration performance of the membrane was assessed by the removal of anionic and cationic dyes. For anionic dyes, the membrane rejection reached a value of 90 % for direct red 80 and 87 % for methyl orange. For the rhodamine B considered as cationic dye, the membrane rejection reached a value of 81 %. The membrane may be considered sustainable since it is inexpensive and emits at least 9.76 kg CO2eq m−2 less than other ceramic membranes during its preparation.

Characterization of Silica Nanoparticles from Pumice as an Aerogel Adsorbent

Pumice is often found around the banks of rivers, this stone is a type of igneous rock formed from volcanic eruptions. One of the compounds contained in pumice is silica. Therefore, the synthesis of silica nanoparticles from pumice using the sol gel method was used because it is simpler and more efficient in terms of cost and processing time. the initial step was by reacting pumice powder and NaOH at 70°C - 80°C then synthesized by adding 2M HCI to form a gel or white precipitate, soaking in ethanol, teos, hexane solutions was then synthesized to become an aerogel. Silica synthesis results into silica aerogels were characterized by FTIR and XRF. From FTIR silanol and siloxane functional groups were found, and the SiO2 composition increased to 93,299% after synthesis.

SINTESIS SILIKA GEL DARI LIMBAH SEKAM PADI (Oryza Sativa) DENGAN VARIASI KONSENTRASI JENIS ASAM

Rice Husk Ash (RHA) is a material that has the potential to be used in Indonesia because of its high production with sampling results during the rice milling process which produces quite a lot of waste, which is equal to 20% of the grain weight with the characteristics of rice husk which is coarse, has low nutritional value, has a high density. low and high ash content. The high content of silica in rice husk can be a reference for its use as a raw material for making silica. Through this research the authors did this to determine variations in the concentration of acid types on the quality of the water content (%) of the resulting silica gel and to determine the characteristics of acid type silica gel. After conducting research using quantitative methods through data collection and data processing, it was found that the concentration of various types of hydrochloric acid (HCl) had a higher level of water content than the type of citric acid (C6H8O7), obtained the concentration of 9 M, while the FTIR test results showed that silica in the type of acid used contained OH groups which identified silanol (SI-OH) absorption range 3450 - 3550 cm-1 and siloxane functional groups (Si-O) absorption ranges of Si-O functional groups, namely 1075 - 1095 cm-1.

Characterization of Silica Nanoparticles from Pumice as an Aerogel Adsorbent

Pumice is often found around the banks of rivers, this stone is a type of igneous rock formed from volcanic eruptions. One of the compounds contained in pumice is silica. Therefore, the synthesis of silica nanoparticles from pumice using the sol gel method was used because it is simpler and more efficient in terms of cost and processing time. the initial step was by reacting pumice powder and NaOH at 70°C - 80°C then synthesized by adding 2M HCI to form a gel or white precipitate, soaking in ethanol, teos, hexane solutions was then synthesized to become an aerogel. Silica synthesis results into silica aerogels were characterized by FTIR and XRF. From FTIR silanol and siloxane functional groups were found, and the SiO2 composition increased to 93,299% after synthesis.

Small-Molecule Electron Transport Layer with Siloxane-Functionalized Side Chains for Nonfullerene Organic Solar Cells.

Active layer materials with silicone side chains have been broadly reported to have excellent long-term stability in harsh environments. However, the application of conjugated materials with silicone side chains in electron transport layers (ETLs) has rarely been reported. In this research, we synthesized for the first time a siloxane-modified perylene-diimide derivative (PDI-OSi) consisting of a side-chain substituent of siloxane and a conjugated group of perylene-diimide (PDI). The inserted siloxane functional groups not only can strengthen the light transmittance of PDI-OSi but also can remarkably expand its solubility and improve the film-forming ability and air stability of the material. Second, introducing siloxane-containing side chains can dramatically lower the work function and interfacial barrier of the electrode, thereby achieving a favorable ohmic contact. In addition, the moderate surface energy of siloxane functional groups makes PDI-OSi hydrophobic, which is conducive to forming excellent miscibility with hydrophobic active layers to promote charge transfer. When PDI-OSi is used as an ETL in organic solar cells (OSCs), operative exciton dissociation and more favorable surface morphology enable OSCs to realize a power conversion efficiency (PCE) of 13.99%. These results indicate that side-chain engineering with siloxane pendants is a facile strategy for constructing efficient OSCs.

X-ray Photoelectron Spectroscopic Study of Some Organic and Inorganic Modified Clay Minerals.

Layered clay systems intercalated with inorganic and organic compounds were analyzed to highlight how XPS can provide information on the different environments surrounding a particular atom as well as provide discernments on the size, coordination, and structural and oxidative transformations of the intercalating/pillaring compounds. XPS data on the intercalation of urea and K-acetate in low- and high-defect kaolinite revealed the interaction of the intercalating group NH2 with the siloxane functional groups in the interlayer surface. The intercalation of HDTMA in Mt demonstrated the use of XPS in monitoring the change in conformation assumed by alkylammonium intercalating compounds in Mt with increasing CEC. Studies on the pillaring of Mt by Al13 and Ga13 by XPS allowed determination of the coordination of the pillaring compound within the Mt layer. Lastly, the intercalation of hexacyanoferrate in hydrotalcite demonstrated the capability of XPS in following changes in the oxidation state of the iron compound. These were gleaned from interpretation of the shifts in binding energies and presence of multiplet splitting in the XPS of the component elements of the minerals or the intercalating compounds.

Silica-Rice Husk as Adsorbent of Cr (VI) Ions Prepared through Sol-Gel Method

One of the heavy metals contained in the textile industry wastewater is chromium (Cr). Chromium hexavalent ions (Cr6+) are highly toxic and its accumulation in the human body will cause various negative impacts. This study aimed to determine the characteristics of silica synthesized by the sol-gel method to gain homogeneity and high purity. Synthesized silica was calcined at 700°C for 4 hours and its performance to adsorb Cr(VI) ions in textile wastewater was investigated. The presence of -OH group from silanol (–Si-OH) was appeared at wavenumber 3367.70 cm-1, meanwhile siloxane functional groups were recorded at 1056.99 cm-1 and 784.38 cm-1 due to the O-Si-O asymmetric stretching and Si-O bending vibration. Optimum conditions of silica to adsorb Cr(VI) ions took place at pH 2 and contact time of 90 minutes by adsorption efficiency of 75,65% and followed the Freundlich isotherm.

Antifouling silicone hydrogel contact lenses via densely grafted phosphorylcholine polymers.

Silicone hydrogel contact lenses (CLs) permit increased oxygen permeability through their incorporation of siloxane functional groups. However, contact lens biofouling can be problematic with these materials; surface modification to increase lens compatibility is necessary for acceptable properties. This work focuses on the creation of an antifouling CL surface through a novel grafting method. A polymer incorporating 2-methacryloyloxyethyl phosphorylcholine (MPC), well known for its antifouling and biomimetic properties, was grafted to the model lens surfaces using surface-initiated atom transfer radical polymerization (SI-ATRP). The SI-ATRP modification generated a unique double-grafted polymeric architecture designed to resist protein adsorption through the presence of a surrounding hydration layer due to the PC groups and steric repulsion due to the density of the grafted chains. The polymer was grafted from model silicone hydrogel CL using a four-step SI-ATRP process. Attenuated total reflectance-Fourier transform infrared spectroscopy and XPS were used to confirm the surface chemical composition at each step of the synthesis. Both the surface wettability and equilibrium water content of the materials increased significantly upon polyMPC modification. The surface water contact angle was as low as 16.04 ± 2.37° for polyMPC-50 surfaces; complete wetting (∼0°) was observed for polyMPC-100 surfaces. A decrease in the protein adsorption by as much as 83% (p < 0.000 36) for lysozyme and 73% (p < 0.0076) for bovine serum albumin was observed, with no significant difference between different polyMPC chain lengths. The data demonstrate the potential of this novel modification process for the creation of extremely wettable and superior antifouling surfaces, useful for silicone hydrogel CL surfaces.

Asymmetric Siloxane Functional Side Chains Enable High-Performance Donor Copolymers for Photovoltaic Applications.

In this work, three benzodithiophene-benzotriazole alternated wide band gap copolymers attaching symmetric or asymmetric conjugated side chains, namely, PDBTFBTA-2T, PBDTFTBA-TSi, and PBDTFBTA-2Si, were developed for efficient nonfullerene polymer solar cells. The symmetry effect of the side chains was investigated in detail on the overall properties of these donor polymers. The results demonstrated that the introduced siloxane functional groups showed less effect on the absorption and frontier orbital levels of the prepared polymers but had a significant effect on the miscibility between these polymer donors and the nonfullerene acceptor. When increasing the content of siloxane functional groups, the miscibility of the polymer donors and Y6 would be improved, leading to the decreased domain size and more mixed domains. Interestingly, the active blend based on PBDTFTBA-TSi with asymmetric side chains exhibited more balanced miscibility, carrier mobility, and phase separation, benefiting exciton diffusion and dissociation. Therefore, a champion power conversion efficiency (PCE) of 14.18% was achieved finally in PBDTFTBA-TSi devices, which was 20.6 and 19.0% higher than the symmetric counterparts of PBTFBTA-2T devices (PCE = 11.76%) and PBDTFBTA-2Si devices (PCE = 11.92%), respectively. This work highlights that the asymmetric side-chain engineering based on siloxane functional groups is a promising design strategy for high-performance polymer donor semiconductors.

SILORANE INCORPORATED WITH HYDROXYAPATITE AND FLUOROAPATITE –TO INVENT A NEW BIOACTIVE RESTORATIVE MATERIAL

Background: There were a number of restorative materials, which were fulfilling the requirements of a dental restorative material partially or somewhat completely with some limitations. 3M ESPE recently introduced a new dental restorative material, Filtek™ Silorane, which was claimed to fulfil the main objective completely, which was even confirmed by the recent studies. In order to make the best available dental restorative material an ideal restorative material it has to be bioactive. This study has been planned for the invention of a Silorane based bioactive material. It was proposed to incorporate the known bioactive materials (Hydroxyapatite and Fluoroapatite) in Silorane and analyze its chemical characterization. The main objective of a restorative dental material is to restore the function and aesthetics of the dental patient. Methods: Hydroxyapatite and Fluoroapatite were synthesized and incorporated in Silorane by 5, 10, 40, 50 and 60% weight ratio. The resultant samples were chemically analyzed by FTIR and Raman Spectroscopy. Results: The incorporation of synthesized Hydroxyapatite and Fluoroapatite into Silorane resulted in the innovation of a new bioactive restorative material. The resultant FTIR and Raman spectra shows that the Silorane incorporated by 40, 50 and 60% hydroxyapatite and fluoroapatite were altering the chemical structure of Silorane while spectrum of the samples with 5 and 10% of hydroxyapatite and fluoroapatite shows the apatites presence without changing the chemical structure of Silorane. Conclusion: A novel bioactive restorative material was invented by the incorporation of synthesized nano-Hydroxyapatite and Fluoroapatite into Filtek™ Silorane. The chemical characterization showed that bond was formed between the apatites and siloxane functional groups which results in the best available dental restorative material.

Phase Transition of SiO2 Nanoparticles Prepared from Natural Sand: The Calcination Temperature Effect

In this paper, we systematically report the synthesis of nano silica powder from natural silica sand by a continuous process. Extraction of sodium silicate from silica sand was through a hydrothermal process, then sodium silicate was ready to be used as a precursor in the form of silicate slurry by coprecipitation process. The silicate slurry of SiO2.XH2O was then dried in a furnace at 150 °C for 4 hours until obtaining a pure white SiO2 powder. At a calcination temperature of 900 °C, the sample was then tested by XRD to analyze the transformation of the crystal phase of SiO2 nanoparticles. Identification of functional group absorption was undertaken by FTIR test, and the particle grain microstructure was analyzed by SEM. At calcination temperature of 900 °C, the SiO2 silica nanoparticles experienced a change of phase from amorphous to crystal or amorphous-cristobalite phase; a shift in stiffness for positions of functional group absorption of Si-O stretching or LO functional groups, Si-O stretching or TO, Si-O-Si bending and Si-O-Si rocking and OH-functional groups occurred; the growth of particle grains happened with a spherical and oval trend, with a larger size. SiO2 nanoparticles were successfully synthesized by a continuous method and 900 °C calcination temperature had a significant effect on structural phase changes, the formation of siloxane functional groups, silanol, and grain growth on SiO2 nanoparticles.

Thermo-mechanical stability of epoxy composites induced with surface silanized recycled carbon fibers

Epoxy composites were prepared using surface silanized chopped carbon fibers (CCFs). Silanized CCFs were synthesized from industrial waste carbon fibers. This work demonstrates the capability of surface silanized chopped carbon fibers to enhance the thermo- mechanical stability of the epoxy composites. The surface silanization of the CCFs to amend the interfacial interaction with epoxy network was done by attaching siloxane functional groups onto CCFs surfaces. Epoxy composites blended with 0.5 and 1 wt % of siloxane decorated CCFs showed a tremendous enhancement in storage modulus in comparison to neat epoxy. This enhancement of composites properties opens up the scope to utilize CCFs for high performance and cost effective epoxy composites. This study opens up the use of juvenile CCFs from waste carbon fibers for their utilization in next generation composites.

Amending the thermo-mechanical response and mechanical properties of epoxy composites with silanized chopped carbon fibers

This study demonstrates the ability of functionalized chopped carbon fibers (CCFs) chosen from industrial waste to improve the thermo-mechanical properties of CCFs/epoxy composites. The defect sites onto the CCFs were created by their oxidation and the oxidized CCFs were covalently linked with siloxane functional groups to conceal their defects. The surface functionalization of CCFs was characterized by a simple chemical route, FTIR and TGA analysis, respectively. The surface morphology of functionalized CCFs showed the generation of highly dense networked globules. Epoxy composites filled with 0.5wt% of siloxane attached CCFs (S-CCFs) showed a tremendous enhancement in storage modulus (∼376%) without sacrificing their thermal stability. Furthermore, the S-CCFs reinforced epoxy composites demonstrate a significant improvement in the tensile and fracture properties. Such enhancement in the mechanical properties can open up the scope for the utilization of CCFs as a potential cost-effective candidate for high-performance next generation structural composites.

A comprehensive study on step-wise surface modification of C60: Effect of oxidation and silanization on dynamic mechanical and thermal stability of epoxy nanocomposite

Fullerenes (C60) are regarded as exceptional reinforcing material in composites for their capability to enrich multi-functional properties. In the present work, pristine C60 has been stepwise modified through oxidation in the presence of nitric acid and then silanized using 3-aminopropyltriethoxysilane (APTES) to generate oxygenated and siloxane functional group elements onto their surfaces. The morphological investigation of oxidized and silanized C60 was done under FESEM and TEM. On the other hand, FTIR spectroscopy and TGA analysis confirms the attachment of oxygenated and siloxane functional groups. The increase in structural defect, creating sites for APTES grafting is evident from Raman spectroscopy. Epoxy nanocomposites were prepared by incorporating 0.5 wt% of pristine and stepwise modified C60. The effect of surface modification of C60 on epoxy nanocomposite is studied under DMA and TGA. The silanized C60/epoxy nanocomposite showed significant enhancement of storage modulus (∼491%) and enhanced intensity of tan δ peak compared to the neat epoxy. This is mainly attributed to high energy absorption during viscoelastic motion. From the TGA, silanized C60/epoxy nanocomposite showed modest increment in initial decomposition temperature. This behavior is suggestive for potential espousal of silanized C60 to enhance the stiffness and molecular relaxation of epoxy nanocomposites.

Regulating Nucleation Kinetics through Molecular Interactions at the Polymer–Solute Interface

Heterogeneous nucleation is ubiquitous both in nature and in industrial practice; therefore, the ability to inhibit or enhance the kinetics of a crystallization process is essential in many scientific and technological areas. In order to better understand the role of surface functionality in regulating the nucleation rate, six commercially available polymers have been used as heteronucleants of acetaminophen (ACM) molecules: polydimethylsiloxane (PDMS) with siloxane functional groups Si–O–Si forming the backbone of silicones, partially fluorinated elastomer polyvinylidenedifluoride (PVDF), polystyrene (PS) having weak electron-donor phenyl rings, poly(n-buthyl methacrylate) (PnBMA) showing ester functionality, polyimide (PI) that includes both hydrogen-bond acceptor imide functionality and carbonyl groups, ethylene/acrylic acid (EAA) copolymer with carboxyl moiety. Experimental results from induction time statistics, van Oss–Chaudhury–Good model of surface energetics, and powder X-ray diffraction (PXRD) a...

Synthesis and characterization of new, liquid, branched poly(methylvinylborosiloxanes)

Abstract New liquid branched poly(methylvinylborosiloxanes) (br-PMVBS) of random structure were synthesized in three steps. By reacting boric acid with an excess of dimethyldichlorosilane (Me2SiCl2) in dry ether a “borosiloxane precursor”: tris(chlorodimethylsilyl) borate B(OSiMe2Cl)3 was prepared. In the second step of synthesis ether solution of B(OSiMe2Cl)3 was added to a mixture of appropriate organic chlorosilanes (Me2SiCl2, MeViSiCl2, MeSiCl3, and Me3SiCl) and all reagents were reacted with stoichiometric amounts of water, in the presence of pyridine (as an acceptor of HCl), in dry ether, at low temperature (usually at -10 to 0 C). In order to fully react (“to block”) trace silanol groups, reactions of intermediate PMVBS with additional batches of Me3SiCl were carried out in the third step, C5H5N·HCl was filtered off and washed with a dry ether. The solvent was distilled off from filtrates and low molecular weight siloxane oligomers were removed by a vacuum distillation at 130-150 C. Chemical structures of br-PMVBS were confirmed by elemental analysis and spectroscopic methods (FTIR, emission atomic spectroscopy ICP-AES, and NMR: 1H, 29Si and 11B). On the basis of analysis of their 29Si-NMR spectra the microstructure of polysiloxane chains was proposed. The prepared br-PMVBS had in their structures: triple branching borosiloxane units: BO1.5 and in some cases methylsiloxane moiety CH3SiO1.5 (T). They contained linkages: Si-O-Si, Si-O-B, vinyl(methyl)siloxane functional groups (CH2=CH)MeSiO (Dvi), dimethylsiloxane mers (CH3)2SiO (D), and non-reactive trimethylsiloxy terminal groups (CH3)3SiO0.5 (M), but they did not have: hydroxyl functional groups: Si-OH and B-OH, and sensitive to water B-O-B linkages. Molecular weights of br-PMVBS (Mn = 1500-3300 g/mol; Mw = 3800-7400 g/mol) and their polydispersity (Mw/Mn = 2.0-2.5) were determined by a size exclusion chromatography (SEC).

PEGylated polyethyleneimine grafted silica nanoparticles: enhanced cellular uptake and efficient siRNA delivery

The present paper reports the utilization of hybrid nanocomposite particles consisting of PEI25k-PEG5k copolymer grafted silica nanoparticles (SiO(2)NPs) for enhanced cellular uptake and siRNA delivery. High-resolution transmission electron microscopy and dynamic light scattering measurements ensured the average particle size of the final hybrid component as 45nm (core SiO(2), 28-30nm and shell PEI25k-PEG5k, 12-15nm). Surface morphology from atomic force microscopy analysis showed the significant relationship between the particle size and shape. (29)Si and (13)C cross-polarization-magic angle spinning solid state nuclear magnetic resonance (NMR), (1)H-NMR, and Fourier transform infrared spectroscopy were used to obtain the relevant structural information (such as Q3, silanol; Q4, siloxane functional groups of SiO(2)NPs; resonance shifts and bending vibrations of PEI25k, -CH(2)-CH(2)-NH-; and PEG5k, -CH(2)-CH(2)-O-) from copolymer nanoparticle. Stable complexation of siRNA and nanocomposite particle (wt.%:wt.%) was achieved from 1:5 to 1:15 ratio. Nanocomposite particle (N/P) ratio and siRNA concentration determine the stability and knockdown efficiency of the PEI25k-PEG5k-graft-SiO(2)NPs-siRNA complexes. It was shown that highly positively charged (zeta potential, +66mV) PEI25k-PEG5k-graft-SiO(2)NPs result in strong affinity with negatively charged siRNA. Confocal microscopy showed intensified cellular uptake of siRNA into cytoplasm of A549 cancer cell utilized for in vitro study. In conclusion, the coherence, graft density of copolymer-SiO(2)NPs, and siRNA concentration were found to strongly influence the stability, and hence determine the knockdown efficiency, of PEI25k-PEG5k-graft-SiO(2)NPs-siRNA complexes.

Heterogenization of Organometallic Molybdenum Complexes with Siloxane Functional Groups and their Catalytic Application

Abstractη5‐CpMo(CO)3R complexes containing siloxane functional groups [(CH2)3Si(OMe)3 or (CH2)Si(OEt)3] attached to either the cyclopentadiene ligand or directly to Mo were grafted on the mesoporous materials MCM‐41 and MCM‐48 by reaction of the OR (R=Me, Et) moieties in the silane ligand and surface silanol groups (Si‐OH). For the sake of comparison mesoporous materials modified with silane groups were reacted with Na+[CpMo(CO)3]−. The XRD, N2 adsorption‐desorption, and TEM analyses provide strong evidence that the mesoporous structure of the supporting material retains its long‐range ordering throughout the grafting process, despite significant reductions in surface area, pore volume and pore size. The appearance of strong IR bands around 2016 and 1956 cm−1 on the grafted samples also shows that the η5‐CpMo(CO)3R complexes have been successfully grafted. Elemental analysis reveals that the grafted samples contain 0.3–3.5 wt % Mo. 29Si CP MAS‐NMR spectra give clear evidence for a reduction in the numbers of the Q3 and Q2 sites. The formation of new peaks around −49.8, −57.9, and −66.2 ppm (T1, T2, and T3) indicates esterification of silanol groups by the alkoxy groups of the silane ligand. Both the in situ and ex situ prepared samples show good catalytic activity for the epoxidation of cyclooctene.