Tetramethoxysilane Research Articles

Siliceous‐based monolithic materials coated with a hydroxyapatite layer: Preparation and investigation of drug affinity by Raman spectroscopy

AbstractMonolithic materials based on silica and hydroxyapatite was applied as tool for investigation of interactions between bone and potential antiresorptive drugs. First type of material was created on the basis of tetramethyl orthosilicate and trimethoxymethylsilane. Second type of material contained additionally chitosan in its structure. Ceramic fraction of monoliths was prepared in two ways: by incorporation of hydroxyapatite during crosslinking or by using soaking method (hydroxyapatite mineralization on the surface). Monolithic materials were prepared in two different forms: in the form of a cylinder and as a filling of a needle for monolithic in‐needle extraction (MINE) device. Several techniques were applied to evaluate the properties of 19 prepared materials: energy dispersive X‐ray spectroscopy, scanning electron microscopy, and Raman spectroscopy, which allowed to confirm and characterize occurred hydroxyapatite layer. Sorption–desorption investigation, with the sodium risedronate as test compound, was made with using ultraviolet‐visible spectroscopy, to assess the affinity of the bisphosphonate for the ceramic layer of the material as a bone substitute. One of 15 prepared MINE devices exhibits sorption ability of risedronate equal to 97%.

Sustainable and Self‐Enhanced Electrochemiluminescent Ternary Suprastructures Derived from CsPbBr3 Perovskite Quantum Dots

AbstractLead halide perovskite quantum dots (QDs) are promising electrochemiluminescence (ECL) nanoemitters due to their fascinating photophysical properties. However, due to their poor structural stability against the external environment, the trade‐off between their colloidal stability and carrier injection/transport efficiency is a major challenge in the advancement of perovskite‐based ECL technology. In this work, intense and stable ECL from CsPbBr3 (CPB) QDs is achieved by simultaneously encapsulating CPB QDs and coreactant (CoR) into in situ generated SiO2 matrix via hydrolysis of tetramethyl orthosilicate. The well‐designed architecture of the as‐obtained CPB‐CoR@SiO2 nanocomposites (NCs) guarantees not only greatly improved stability thanks to the peripheral SiO2 protecting matrix, but also efficient self‐enhanced ECL between CPB and the intra‐coreactants. Consequently, by elaborately selecting the CoR molecules with different tertiary/secondary amines and functional groups, multifold higher (up to 10.2 times) ECL efficiencies are obtained for the CPB‐CoR@SiO2 NCs alone in reference to the standard Ru(bpy)32+/tri‐n‐propylamine system. This work provides an efficient design strategy for obtaining stable and highly efficient ECL from perovskite QDs, and offers a new perspective for the development and application of perovskite‐based ECL system.

Fabrication of Hollow Silica Nanospheres with Ultra-High Acid Density for Efficient Heterogeneous Catalysis

Hollow silica nanospheres with ultra-high acid density were fabricated successfully via sulfonation of phenyl-functionalized hollow silica nanospheres, which were synthesized through a single micelle (F127 (EO106PO70EO106))-templated method, with phenyltrimethoxysilane and tetramethoxysilane (TMOS) as silane precursors under neutral conditions. The density of sulfonic acid reached as high as 1.97 mmol/g. The characterization results of 31P-NMR using triethylphosphine oxide as a probe molecule suggested that the acid strength of hybrid solid acids could be systematically tuned by tuning the content of sulfonic acid and higher acid density results in stronger acid strength. Attributed to the unique hollow structure and high-acid density, the sulfonic acid-functionalized hollow silica nanospheres exhibited good catalytic performance in the condensation reaction of benzaldehyde with ethylene glycol. Notably, this study found that the catalytic activity was significantly influenced by the acid density and the ultra-high acid loading was beneficial for the activity due to the enhanced acid strength. This novel solid-acid catalyst also showed good recyclability and could be reused for at least 11 runs.

Poly(Vinyl Alcohol) Cryogels Formed from Polymer Solutions in Dimethyl Sulfoxide with Tetramethoxysilane Additives

Organic–inorganic hybrid cryogels of poly(vinyl alcohol) (PVA) containing silica inclusions (SiO2) were obtained and studied. Such inclusions were formed in the course of hydrolytic polycondensation (sol-gel process) of tetramethoxysilane (TMOS) introduced into concentrated polymer solutions in dimethyl sulfoxide (DMSO). PVA concentration in these solutions was 60, 80 or 100 g/L; while the concentration of TMOS was varied in a range of 0.15–0.61 mol/L. The polymer solutions were subjected to the cryogenic treatment at temperatures by 40 °С lower than DMSO crystallization temperature (+18.4°C). The frozen samples were thawed out at a heating rate of 0.03°/min. It is shown that moderate freezing at −21.6 °C, then frozen storage and subsequent thawing of the initial reaction mixture PVA/DMSO/TMOS/acid catalyst resulted in the formation of strong macroporous PVA/SiO2 cryogels. Such cryogel materials are hybrid systems, because the gel-forming polymer and the silica containing moieties belong to the content of the gel phase. The basis of this intermolecular interaction is hydrogen bonding between OH groups of the adjacent chains. This leads to the formation of modified microcrystallinity zones that perform as the nodes of the three-dimensional network of cryogels. The effects of significant increase in their rigidity and heat-resistance with increasing PVA and TMOS concentration in the initial feed were also observed. It was shown that the success of the synthesis of transparent elastic and heat-resistant PVA/SiO2 cryogels depends on the choice of the optimal ratio between the precursors and the combined effect of the liquid (methanol and water) and silicon-containing components on the formation of multiple hydrogen bonds and microcrystallites.

Preparation and chiroptical properties of cellulose chlorophenylcarbamate–silica hybrids having a chiral nematic mesomorphic structure

An attempt was made to fabricate optically functional cellulosic–silica hybrid materials wherein a helically ordered mesomorphic structure of the cellulosic component was fixed. Cellulose 3-chlorophenylcarbamate (3Cl-CPC) and cellulose 4-chlorophenylcarbamate (4Cl-CPC) were synthesized by carbanilating reaction of cellulose with 3-chlorophenyl or 4-chlorophenyl isocyanate in a homogeneous solution system. The hydrophobic cellulose derivatives were examined for the solubility and liquid crystallinity in various solvents containing alkoxysilane as a main component. Concentrated (∼40 wt%) solutions of 3Cl-CPC in 3-aminopropyltrimethoxysilane (APTMS) and those of 4Cl-CPC in a mixed solvent of tetramethoxysilane (TMOS)/N,N-dimethylformamide (DMF)/dichloroacetic acid (DCA) formed a chiral nematic mesophase to impart vivid reflection colors. These liquid crystalline solutions were subjected to a sol–gel conversion process of the respective alkoxysilane components in moist air. In the process for the 4Cl-CPC lyotropic system, we utilized a "surface-coating solvent" consisting of TMOS/phenyltrimethoxysilane/DCA to facilitate the sol–gel reaction of TMOS and also to preserve the reflective coloration. Thereby a left-handed chiral nematic hybrid series of 4Cl-CPC–silica was successfully obtained as a monolithic glassy bulk showing iridescent colors. The 3Cl-CPC/APTMS lyotropics were readily converted into a colored solid form without any coating solution, resulting in production of a right-handed chiral nematic series of 3Cl-CPC–silica. Besides investigating the chiroptical characteristics of the liquid crystalline solutions and hybrids, we preliminarily tried separating a racemic compound into two enantiomers by open column chromatography using the cellulosic–silica hybrids as a filler material of the column.

Stirring-assisted orientation of silver nanowires in sol-gel silica

One-directional alignment of Ag nanowires (AgNWs) embedded in silica matrix was achieved by means of the sol-gel fabrication process by stirring the precursor solution consisting of tetramethyl orthosilicate (TMOS) and AgNW during gelation. The parallel orientation of AgNWs along the stirring direction was confirmed in the sliced composite by optical microscopy. The optical function of the obtained composite as polarizer was demonstrated by transmission measurement with polarized light. The polarization response was found to be limited and can be explained with the buckling of AgNWs formed during the condensation reaction.

Development of hydrogen-selective dimethoxydimethylsilane-derived silica membranes with thin active separation layer by chemical vapor deposition

Novel hydrogen-selective amorphous silica membranes were developed by chemical vapor deposition (CVD) method using dimethoxydimethylsilane (DMDMS) as the silica precursor. The preparation conditions were optimized by varying the DMDMS saturated vapor concentration in the CVD reactor and the CVD time. The membrane prepared under optimized conditions demonstrated excellent hydrogen-selective performance, exhibiting a hydrogen permeance of 2.8 × 10−7 mol m−2 s−1 Pa−1 at 773 K, which is approximately three times larger when compared with silica membranes prepared with tetramethoxysilane (TMOS). And the ideal selectivity of hydrogen to nitrogen at the same temperature was 2.3 × 103. The estimation of pore size by the normalized Knudsen-based permeance (NKP) method and the structural analysis by XPS indicated that the DMDMS-derived membrane possessed a thinner active separation layer compared with the TMOS-derived membrane, while the pore size was comparable. Thus, membrane thickness was influenced by the slight difference in the chemical structures of the silica precursors, resulting in a higher hydrogen permeance. Finally, excellent hydrothermal stability of the DMDMS-derived membrane was demonstrated.

Optical and visual experimental characterization of a glazing system with monolithic silica aerogel

Aerogel is a promising building envelope material that can be used to improve thermal and lighting performance. In monolithic form, aerogels allow visual interaction between the built and outdoor environments, unlike aerogels in granular form. However, the high production cost of large monoliths limits their use. In this work, monolithic silica aerogels were fabricated using tetramethyl orthosilicate as the precursor in a base-catalysed recipe, and a novel rapid supercritical extraction method. The method produces transparent aerogel monoliths in as little as six hours. A 30 × 30 cm glazing sample was constructed from nine 15-mm-thick aerogel monoliths sandwiched between two pieces of 4.7-mm-thick float glass. The glazing sample was characterized in terms of directional and hemispherical optical and visual properties. Measurements were made with an in-house-constructed spectrophotometer equipped with a 75-cm-diameter integrating sphere in the 380- to 2300- nm wavelength range with variable incidence angles. The light and direct solar transmittance are 0.69 and 0.62, while the light and direct solar reflectance are 0.25 and 0.19, respectively. The sample is also characterized by a high general colour rendering index (Ra = 96), allowing indoor visual comfort. Gonio-photometric and directional spectral transmittance measurements show negligible visual distortion and colour variation at different observation angles. The light transmittance of the prototype is lower than that of glazing units present on the market, but about 10% higher than an equivalent unit with granular aerogel. This performance is promising for applications where view through a window is required. However, the size of the samples currently fabricated with the innovative process is limited to 14 × 14 cm and they are characterized by some optical defects that must be removed if the process is to be used for commercial product.

Synthesis, Characterization, and Investigation of Inhibitor Release of the Anticorrosion Sol–Gel Hybrid Nanocomposite Coatings

Corrosion protective coatings were developed on 1050 aluminum alloy through the sol–gel process using 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetramethoxysilane (TMOS), and diethylenetriamine (DETA) as the cross-linking agent. Two organic corrosion inhibitors (2-mercaptobenzothiazole and 2-mercaptobenzimidazole) were applied to induce inhibition properties. Salt spray method was employed to evaluate the corrosion protection performance. It was found that organic inhibitors improved the corrosion resistance of the coatings. Formation of silica networks from two precursors of GPTMS and TMOS in the presence of DETA curing agent was confirmed by FTIR. Distribution of silicon and sulfur, surface morphology and the presence of nanoparticles in the matrix were studied by SEM, EDX and TEM techniques. Physical and thermal properties of the coatings were investigated by water contact angle, Pull Off and DMTA tests, respectively. The results revealed that the presence of the organic inhibitors decreased the hydrophilicity and increased adhesion strength but has no significant effect on thermal properties. The controlled release of MBI was also investigated by UV-Vis spectrophotometry.

Organically-modified silica aerogels: A density functional theory study

The primary particles of silica aerogels resulting from three different mixtures of precursors – 50% tetramethylorthosilicate (TMOS)/50% vinyltrimethoxysilane (VMTS); 50% tetraethylorthosilicate (TEOS)/50% aminopropyltriethoxysilane and 50% TEOS/50% glycidylpropoxi – as well as aerogels of pure TMOS and VTMS, have been studied by quantum mechanics density functional theory calculations (DFT), at the B3LYP/6-311+G(d,p) level of theory). Thermo-chemical calculations have indicated that cage structures are the most favored for all materials, followed by other species (linear and cyclic) with high degrees of condensation. A vibration mode analysis based on a numerical model fitted to experimental infrared spectra, has allowed the identification of the most representative silica clusters for all the materials studied. The resulting theoretical spectra were close to their experimental counterparts. Analysis of calculated and experimental 29Si-NMR spectral data generally corroborated the derived model.

Microwave Assisted Synthesis of Polyvinylbutyral‐silica Composites for Mercury Removal Application

AbstractNovel polyvinylbutyral‐silica composite was synthesized via sol‐gel route under microwave conditions for removal of mercury metal from its synthetic aqueous solution. Tetramethoxysilane (TMOS) was used as silica precursor for in situ synthesis of silica onto polyvinylbutyral (PVB) which acted as template as well as capping agent. The synthesized composites were further treated thermally at various stages of elevated temperature in presence of air in a muffle furnace. The synthetic parameters optimized for better mercury removal ability and further characterized using X‐rays diffraction, Scanning Electron Microscopy, Fourier Transform Infrared spectroscopy and thermal analytical methods. The mercury adsorption was studied at various adsorption parameters such as pH, dose, contact time, temperature, mercury concentration etc., to achieve the maximum mercury adsorption. The equilibrium was achieved at 24 h with approximately 95% mercury removal at pH value 8 and 40 °C temperature. The adsorption isotherm as well as adsorption kinetic studies also performed to understand the pattern of adsorption.

Tailoring structure and properties of silica aerogels by varying the content of the Tetramethoxysilane added in batches

Abstract Silica aerogels with high optical transparency and ultra-low thermal conductivity are ideal candidates for energy-saving windows. Often such applications require rather exquisite control of microstructure (i.e., cluster size and cluster packing geometry). In this research, a series of silica aerogels with the same composition and density but different microstructures and properties are prepared by varying the content of the Tetramethoxysilane (TMOS) added in batches. It was found that the mean pore size and thermal conductivity of the silica aerogels initially decrease with the decrease in the content of the pre-added TMOS before bottoming out and eventually increasing again, while the specific surface area, pore volume and light transmittance show the reverse change trend. Compared with the conventionally initial addition of total TMOS, the specific surface area and transparency ratio of the silica aerogels prepared under the optimum level of the pre-added TMOS increase from 845 to 1060 m2/g and from 71% (550 nm) to 88% (550 nm), respectively. Meanwhile, the thermal conductivity of the silica aerogels decreases from 24.6 to 20.2 mW/(m∙K) with the mean pore size decreases from 20.7 to 16.6 nm. This method provides a new approach to design structure and properties of silica aerogels.

Preparation of mixed-mode stationary phase for high performance liquid chromatography with ground hybrid silica monolithic material

With polyethylene glycol as a porogen, vinyltrimethoxysilane (VTMS) and tetramethoxysilane (TMOS) as silica precursors, a hybrid silica monolithic material was obtained under the catalysis of acetic acid and thermally decomposed urea. The silica monolithic material was ground by a ballmill, treated with tris(hydroxymethyl)aminomethane (Tris), then washed and dried to obtain silica particles with particle size~3 μm. The effects of different reaction conditions on the particle size, surface morphology and dispersibility of silica particles were investigated. When the volume ratio of TMOS to VTMS was 3:1, it was observed that silica particles with a pore diameter of 7.5 nm and a specific surface area of 245 m2/g were obtained. The resultant silica particles were modified by binding with chlorodimethyloctadecylsilane (C18) and by the thiol-ene click reaction to obtain a mixed-mode type stationary phase. The test results showed that the silica packing materials prepared in this work has certain applicability.

Azamacrocycles and tertiary amines can be used to form size tuneable hollow structures or monodisperse oxide nanoparticles depending on the 'M' source.

We show that the azamacrocycle 'cyclam' (1,4,8,11-tetraazacyclodecane) in conjunction with a silicon catecholate ion generates novel hollow tetragonal tube-like crystalline materials [(C6H4O2)3Si][C10H26N4]·H2O, whose dimensions can be tuned according to the pH of the reaction medium. The synthesis approach was successful for both silicon and germanium and we hypothesise that a range of other catecholate precursors of elements such as iron could be used to generate a large array of inorganic materials with interesting morphologies. The synthesis approach can be extended to tertiary diamines with functional group spacing playing an important role in the efficacy of complexation. Of the molecules explored to date, a C2 spacing (N,N,N',N'-tetramethylethylenediamine (4MEDAE)), leads to the most efficient structure control with hollow hexagonal tube-like structures being formed. In addition, we show that azamacrocycles, in the presence of unbuffered tetramethoxysilane (TMOS) solutions can be used to manipulate silica formation and provide a fast (ca. 10 minutes) synthesis route to particles whose diameter can be tuned from ca. 20 nm to several hundreds of nm under reaction conditions (no extremes of pH) that make the sols suitable for direct use in biotechnological applications.

Synthesis of Hybrid Monolithic Columns Using a Click Chemistry Reaction for Application in Capillary Liquid Chromatography

Hybrid monolithic columns present characteristics of both silica and organic monoliths, such as good mechanical properties, wide pH tolerance, high permeability and stability and little swelling or shrinkage. A common way to prepare this type of material is by using alkoxysilanes and organic monomers via the sol-gel process and click chemistry reactions. In this paper, a co-condensation organic-silica hybrid monolith was prepared based on tetramethoxysilane (TMOS) and vinyltrimethoxysilane (VTMS) as precursors for the sol-gel process. The hybrid monolithic matrix was modified with dodecanethiol through the thiol-ene click chemistry reaction and the resulting material was compared with a dodecanesilane bonded phase column, in order to evaluate the differences in the chromatographic performance of a stationary phase prepared by a classic reaction or by a thiol-ene click reaction. Additionally, the stability of the thiol-ene column over time was evaluated. The effects of different synthetic proportions were investigated in detail by scanning electron microscopy (SEM), scanning capacitively coupled contactless conductivity detection (sC4D), Fourier-transform infrared spectroscopy (FTIR) and retention behavior in capillary liquid chromatography (cLC). The hybrid monolithic column prepared with dodecanethiol was the best one for the separation of alkylbenzenes and polycyclic aromatic hydrocarbons by cLC-UV.

Transfer and Reactivity of Hydrogen Sulfide with Immobilized Hemeproteins in Polymeric Matrix

Hydrogen sulfide (H2S) has been related to be toxic and to have a role in human physiological functions. Therefore, there is a necessity to comprehend ways to scavenger hydrogen sulfide from different media. Here, we used recombinant metaquo-Hemoglobin I (metHbI) from Lucina pectinata and metaquo-myoglobin (metMb) encapsulated in the tetramethyl orthosilicate gel (TMOS), to facilitate the understanding of H2S transfer toward these metaquo-hemeproteins. In this sol-gel environment, metHbI binds and releases H2S with rate constants of 0.0597 M-1·s-1 and 6.67 × 10-5 s-1, respectively. The process generates an H2S affinity constant (kon/koff) of 8.9 × 102 M-1, which is 107 lowers than the analogous constant in solution (6.3 × 109 M-1). Although the H2S koff for the rHbI-H2S complex is almost similar with both sol-gel and solution. To further understand how the H2S koff from rHbI-H2S in solution (5 μM) is influenced by the protein concentration gradient, metHbI and metMb (25 μM) encapsulated in TMOS sol-gel. Under these circumstances, the H2S transfer from a solution of the rHbI-H2S complex to encapsulated hemeprotein resulted in koff values of 1.90 × 10-4 s-1, and 2.09 × 10-4 s-1 leading to the formation of rHbI-H2S and Mb-H2S species, respectively. The results suggest that the: 1) extreme ionic TMOS construct limits the H2S pathways to reach the hemeprotein active center, 2) possible interaction with metHbI hydrophilic forces increases the hydrogen bonding networking and decreases the H2S association constant, 3) hemeproteins concentration gradients between solution and sol-gels also influence its hydrogen sulfide transfer. In the presence of oxygen or hydrogen peroxide metMb generated a mixture of Mb-H2S and sulfmyoglobin derivative, while encapsulated metHbI reaction did not produce the sulfheme species. Consequently, the results show that metHbI encapsulated in TMOS is an excellent trap for H2S from solution or gas media.

Synthesis and physicochemical characterization of silica aerogels by rapid seed growth method

Thanks to the high optical transparency and ultra-low thermal conductivity, silica aerogels are ideal materials for energy-saving windows. However, their preparation is commonly based on either one-step base-catalyzed method, or two-step acid-base catalyzed method, which is difficult to inhibit the aggregation of clusters while keeping the size of clusters as small as possible and thus degrading silica aerogel's properties. Here, a new idea for synthesizing silica aerogels is presented from the viewpoint of controlling the growth and aggregation of silica clusters. A certain amount of Tetramethoxysilane (TMOS) used as seed precursor is firstly added into the mixture of methanol and distilled water for hydrolysis. A certain time later, the additional TMOS and a defined amount of ammonia are added to the obtained sol for promoting the rapid formation of the gel in several minutes. The silica aerogels prepared by this method have higher optical transparency and lower thermal conductivity than those prepared by the other two methods. This approach may also shed substantial light on controlling the microstructure of other materials prepared by sol-gel process.

Shaping Silica Rods by Tuning Hydrolysis and Condensation of Silica Precursors.

We present the synthesis of colloidal silica particles with new shapes by manipulating the growth conditions of rods that are growing from polyvinylpyrrolidone-loaded water-rich droplets containing ammonia and ethanol. The silica rods grow by ammonia-catalyzed hydrolysis and condensation of tetraethoxysilane (TEOS). The lengthwise growth of these silica rods gives us the opportunity to change the conditions at any time during the reaction. In this work, we vary the availability of hydrolyzed monomers as a function of time and study how the change in balance between the hydrolysis and condensation reactions affects a typical synthesis (as described in more detail by our group earlier1). First, we show that in a “standard” synthesis, there are two silica growth processes occurring; one in the oil phase and one in the droplet. The growth process in the water droplet causes the lengthwise growth of the rods. The growth process in the oil phase produces a thin silica layer around the rods, but also causes the nucleation of 70 nm silica spheres. During a typical rod growth, silica formation mainly takes place in the droplet. The addition of partially hydrolyzed TEOS or tetramethoxysilane (TMOS) to the growth mixture results in a change in balance between the hydrolysis and condensation reaction. As a result, the growth also starts to take place on the surface of the water droplet and thus from the oil phase, not only from inside the droplet onto a silica rod sticking out of the droplet. Carefully tuning the growth from the droplet and the growth from the oil phase allowed us to create nanospheres, hollow silica rods, hollow sphere rod systems (colloidal matchsticks), and bent silica rods.

Silica-based hybrid porous layers to enhance the retention and efficiency of open tubular capillary columns with a 5 μm inner diameter

We report on possibility to enhance the hydrophobicity of octadecylsilylated silica-based porous layered open tubular (PLOT) columns with an inner diameter (i.d.) of 5 μm by applying hybrid tetramethoxysilane (TMOS)/methyltrimethoxysilane (MTMS) layers with inserted methyl groups. Due to this higher hydrophobicity, thinner porous layers suffice to achieve similar retention factor (k) as in octadecylsilylated silica-based PLOT columns synthesized using TMOS only. Since thinner layers have a lower intra-layer mass transfer resistance, this in turn allows to obtain superior column efficiencies in comparison with separations carried out with TMOS-based PLOT columns at the same retention. Since layer thickness contributes to the C-term type of band broadening, this is most pronounced at high velocities. Typical gains in column efficiency at a reduced velocity of νi = 30 are on the order of 15%.Preparing the hybrid PLOT columns in 5 μm i.d.-capillaries with a length of 0.4 m using different TMOS/MTMS preparation mixtures leads to different layer thickness in the capillaries. It is shown that column efficiencies for the most retained compound (k = 0.9–1.5) went from N = 101,000 for PLOT columns with a layer thickness (df) of 250 nm, over N = 95,000 for df = 320 nm to N = 89,000 for df = 400 nm, corresponding to plate heights (H) in the order of 3.5–3.9 μm (reduced plate heights (h = 0.8–1.0)). By applying the same preparation mixtures for much longer capillaries of 1.3 m, a high repeatability of the volumetric phase ratio (m) (difference <1%) and the k-values (difference <5%) was observed between the 0.4 m and 1.3 m PLOT columns. In addition, also a very similar band broadening was obtained, as the h-values in the longer columns coincided well (order of a few % difference) with the reduced plate height curves measured in the shorter columns. The effect of the retention factor and layer thickness on these reduced plate height curves furthermore fits well with the Golay-Aris theory. Depending on the layer thickness, plate numbers in the longer capillary columns were varying from N = 282,000 to N = 379,000 for the most retained compound.

Nanostructured Membranes from Soft and Hard Nanoparticles Prepared via RAFT‐mediated PISA

AbstractReversible addition‐fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) is used to prepare a series of near mono‐dispersed poly(2‐(dimethylamino)ethyl methacrylate)‐poly(benzyl methacrylate) (PDMA‐PBzMA) diblock copolymer nanoparticles in an ethanol–water binary mixture via polymerization‐induced self‐assembly. A relatively long PDMA (DP = 88) chain transfer agent is targeted to ensure that only spherical morphologies are obtained. High (&gt;99%) BzMA monomer conversions can be achieved within 24 h when targeting degrees of polymerization (DP) of up to 1000. The resulting particles are analyzed using dynamic light scattering and transmission electron microscopy (TEM). Particles with PBzMA DPs of 500 and 1000 are used as templates for deposition of silica particles. TEM images confirm that tetramethyl orthosilicate precursor is successfully converted into silica sols that are deposited on the surface of the spherical polymer nanoparticles. Thin film membranes are then prepared from these silicified spherical particles (hard spheres) as well as the initial spherical particles devoid of silica coating (soft spheres). These membranes are fully characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and water filtration test.