Hybrid Silica Particles Research Articles

Effect of hybrid reinforcements on the curing kinetics and mechanical properties of light‐cured polymer composites

AbstractLight‐cured polymer composites incorporating particle reinforcements have been adopted for a wide range of engineering applications. Nevertheless, micro‐filled composites exhibit insufficient strength despite good abrasion resistance. Conversely, nano‐filled counterparts possess enhanced strength but easily generate particle agglomeration. Hybrid filling has therefore been utilized in previous studies to combine the advantages of different components, but conclusive results have not been obtained. Within this study, the effects of hybrid filling on the strengthening mechanism and curing kinetics of light‐cured polymer composites were investigated by multi‐scale mechanical tests, in‐situ near‐infrared spectroscopy, scanning electron microscope, and finite element simulations. It was found that hybrid filling led to an average increase in Young's modulus by ~3.94%, the hardness by ~5.81%, the tensile strength by ~10.44%, and the degree of conversion by ~2.54% compared to micro‐filling at the same filler content. Besides, hybrid filling showed more reduced particle agglomeration compared to nano‐scale filling. Finite element analysis revealed that hybrid filling effectively enhanced the load‐bearing capacity of the matrix. Overall, the experimental results unveil a mechanism of particle reinforcement that can be extrapolated to various particle‐filled polymers across different length scales. These findings provide a versatile manufacturing technique for composites with heightened mechanical reinforcement and are expected to guide the application in the field of photo‐polymeric materials.Highlights Light‐cured polymer composites incorporating hybrid silica particles were prepared. The strengthening mechanism was investigated by multi‐scale mechanical tests. Hybrid filling could lead to an increase in material strength compared to micro‐filling. Hybrid filling exhibited reduced particle agglomeration in comparison to nano‐filling.

Mechanical Performance of Hybrid Graphene Nanoplates, Fly-Ash, Cement, Silica, and Sand Particles Filled Cross-Ply Carbon Fibre Woven Fabric Reinforced Epoxy Polymer Composites Beam and Column

The main goal of this study is to reduce the brittleness of a fibre-reinforced cement base structure when exposed to the effects of graphene nanoplates, fly ash, silica, sand, and cement fillers to better understand the effect of hybrid nano/micro particle fillers on the mechanical performance of cross-ply carbon fibre reinforced epoxy resin composites. A three-point bending test through the width was used to measure flexural strength. The impact tests Izod at low impact velocity and Charpy through the thickness were used to determine the dynamic fracture strengths of pre-cracked and non-cracked composite samples. Also, the compressive test method was used to measure the compressive strength of hybrid particles and short glass fibre-reinforced epoxy resin composite square and circular columns. The results show compressive strength and flexural strength. Izod impact energy, Charpy impact energy, and dynamic fracture toughness of hybrid nano/microparticle-filled fibre composites have higher values than virgin fibre composites due to the influence of graphene nanoparticles and perfect interface bonding between two dissimilar molecules of nano and microparticles, which improve the fracture toughness and absorb impact energy. Overall, the results indicate that molecules of nano/microparticle-filled carbon fibre and glass fibre-reinforced epoxy resin composites can be used in aggressive environments because of the improved mechanical properties in comparison to the virgin fibre composites. In addition, SEM micrographs clearly indicate that nano- and microparticles are resistant crack propagation and deboned of matrix fibres.

Controlling Superhydrophobicity and Oleophobicity of Polydimethylsiloxane-Coated Silica Hybrid Particles

Hierarchical functional organic-inorganic hybrid particles for versatile control of surface wettability have attracted much attention in a wide range of applications from makeup cosmetics to anti-smudging optoelectronic devices. In this study, superhydrophobic and oleophobic organic-inorganic hybrid particles were prepared by a simple and systematic fabrication strategy using the synergistic combination of commonly available silica particles and polydimethylsiloxanes (PDMSs) with hydrophobic chain ends. Various types of PDMSs with different chain lengths and chemical structures were surface-grafted to silica microparticles through facile physical dispersion and subsequent thermal treatment to form hydrogen bonds or covalent bonds between the inorganic silica and organic PDMS polymers and thus induce a core-shell structure for the hybrid particles, which imparts superhydrophobicity and oleophobicity to the surface of silica particles. The prepared PDMS-coated silica hybrid particles with long PDMS chains exhibited a water contact angle of 151.2° and an oil contact angle of 15.2° due to the rough surface morphology and hydrophobic long-chain effects. Furthermore, the resulting organic-inorganic hybrid particles were thermally stable up to 420 °C. This controlled approach endowed the organic-inorganic hybrid particles with both superhydrophobic and oleophobic surfaces and, therefore, these particles were proven to be suitable for waterproof applications.

Further Evaluation of the Base Stability of Hydrophilic Interaction Chromatography Columns Packed with Silica or Ethylene-Bridged Hybrid Particles

One of the fundamental attributes of a liquid chromatography column is its stability when exposed to acidic and basic mobile phases. However, there have been relatively few reports to date on the stability of hydrophilic interaction chromatography (HILIC) columns. Here, we report the results of stability evaluations carried out for HILIC columns packed with ethylene-bridged hybrid or silica particles using accelerated conditions, employing a 100% aqueous pH 11.3 ammonium bicarbonate mobile phase at 70 °C. Under these conditions, the primary mode of column failure was a loss of efficiency due to the formation of voids resulting from the hydrolysis of the particles. We investigated the dependence of stability on the surface area of both unbonded and sulfobetaine-bonded ethylene-bridged hybrid stationary phases. The results show a clear trend of stability increasing as the surface area decreases. Several commercially available HILIC columns that are recommended for use with high-pH mobile phases were also evaluated. The results show times to 50% loss of the initial efficiency ranging from 0.3 to 9.9 h. Columns containing unbonded, sulfobetaine-bonded or diol-bonded ethylene-bridged hybrid stationary phases had longer lifetimes than amino-bonded silica or sulfobetaine-bonded, hybrid-coated, superficially porous silica columns.

Ice-phobic polyurethane composite coating characterized by surface micro silicone loops with crumpling edges

This study developed a tactic to attain an ice-phobic polyurethane (PU) composite coating, which was fabricated by incorporating minor dosages of hybrid silica particles and silicone oil (SO) into the formulation of a commercial aerospace PU topcoat. The hybrid silica particles were synthesized by anchoring polydimethylsiloxane (PDMS) oligomers to silica microspheres. Both hybrid particles and SO amalgamate in the surface matrix of PU to induce a spread of wrinkling micro-loops over the coating. This coating surface morphology is structurally different from the well-known slippery liquid-infused porous surface since no liquid bulk is embedded in the surface matrix of PU coating. The icephobic property was characterized on a thermoelectric Peltier cooling plate, over which the frosting extents with cooling in ambient humidity conditions (~75 % RH) were compared. We have identified three coating fabrication factors responding to the delay of frosting inside the condensed water droplets overlying the PU coating. At the same time, they are cooled: the fuzzy PDMS layer on silica microspheres, i.e., hybrid particles, the fusion of SO with the hybrid particles, and the dosages of the hybrid particles and SO applied. Typically, when the PU composite topcoat comprises 0.4 wt% (based on PU matrix) hybrid particles and 0.4 wt% SO of the hybrid particle, it adjourns the onset of frosting to ~ −10 of from - 5.6 °C on the aerospace PU topcoat. This outcome is attributed to the micro round loops with folding edges and peripheric wrinkles that possess low-temperature softness and play a pivotal role in deferring icing inside the overlying water droplets.

Evaluation of the Base Stability of Hydrophilic Interaction Chromatography Columns Packed with Silica or Ethylene-Bridged Hybrid Particles

Stability as a function of mobile phase pH is an important consideration when selecting a chromatographic column. While the pH stability of reversed-phase columns is widely studied, there are relatively few reports of the stability of hydrophilic interaction chromatography (HILIC) columns. We evaluated the stability of silica and ethylene-bridged hybrid HILIC columns when used with mobile phases containing basic buffers. The predominant mode of column degradation observed in our studies was a decrease in efficiency due to voiding, resulting from the hydrolysis of the silica particles. Associated with this were increases in tailing factors. Retention factor changes were also noted but were smaller than the efficiency losses. The dependence of the rate of efficiency decrease on the key variables of temperature, mobile phase pH and water content were studied for an unbonded silica column. The effect of the acetonitrile concentration on the pH of the mixed aqueous/acetonitrile mobile phases was also investigated. Using conditions found to cause a 50% decrease in efficiency after approximately five hours of exposure to the basic solution, we evaluated eight different commercially available HILIC columns containing silica or ethylene-bridged hybrid particles. The results show large differences between the stability of the silica and ethylene-bridged hybrid particle stationary phases, with the latter exhibiting greater stability.

The development of phosphorus-doped hybrid silica sol coating for silk with durable flame retardancy

The fabrication of phosphorus-doped sol-gel coatings for durable flame retardant (FR) modification of textiles are of interest. This study facilely synthesized a novel phosphorus-doped silica sol system using 3-aminopropyltriethoxysilane, glutaraldehyde, diethyl phosphite by simultaneous Kabachnik-Fields and sol-gel reactions. The morphology and chemical structures of hybrid silica particles were studied by TEM, FT-IR and NMR. Then, the hybrid silica sol was applied as durable FR coating to reduce the flammability of silk. The FR property and washing durability, smoke and heat generation capacity, thermal stability, and FR mechanism of coated silk fabrics were explored. The hybrid silica coating displayed good FR performance because of the synergistic action among Si, P and N. The coated fabrics self-extinguished after 25 launderings and had a high LOI value of 28.0% thanks to the covalent grafting of hybrid silica coating on silk fabrics. The explorations on silk residues confirmed the intumescent FR mechanism of coated silk. The hybrid silica coating is promising to functional as feasible and durable FR strategy for silk fabric.

Assessing Stability of Nanocomposites Containing Quantum Dot/Silica Hybrid Particles with Different Morphologies at High Temperature and Humidity

In this study, we investigate the photoluminescence stability of nanocomposites containing quantum dot (QD)/silica hybrid particles against high temperature and humidity. First, hybrid particles wi...

The Influence of Water Content on the Growth of the Hybrid-Silica Particles by Sol-Gel Method

This paper investigates the change in size and morphology of the silica network with the change of water content by sol-gel method. Methyl triethoxysilane (MTES) and tetraethyl orthosilicate (TEOS) were used as co-precursors. The results reveal that the morphology controllable silica network are prepared by changing water content, the size of silica network is in the range in 17–176 nm. There are two ways for the silica nanoparticles to grow in the sol media, condensing with the newly hydrolyzed precursor named monomer-addition model or condensing with the existing silica structure called controlled-aggregation model. As the molar ratio of water/siloxane increases from 1 to 12, the growth process change from the aggregation of oligomers to the condensation between oligomer and hydrolyzed precursor, and the final morphology of silica nanoparticles changes from a network structure to a monodisperse particle structure. When the water content reaches a very high value with the molar ratio of water/siloxane ≥12, the growth process of silica nanoparticles is dominated by the monomer-addition mechanism. The addition of MTES as co-precursor favors the formation of the network structure.

Transmission Electron Microscopy: Novel Application of Established Technique in Characterization of Nanoparticles as Drug Delivery Systems.

Nanotechnology presents a modern field of science that in the last twenty-five years plays a dominant role in the biomedicine. Different analytical methods are used for evaluation of the physico-chemical properties of nanoparticles including chromatography, electrophoresis, X-ray scattering, spectroscopy, mass spectrometry, zeta potential measurement and microscopy on which this article will focus. Herein, we present novel application of the long-established TEM technique that is focused on characterization and evaluation of various nanoparticles in development of drug delivery systems. Transmission electron microscopy images were taken of samples from native nanoparticles, nanoparticles labeled using stannous chloride labeling procedure, inorganic silica nanoparticles loaded with budesonide and native micelles and micelles carrier of anticancer drug camptothecin. In the case of radiolabeled nanoparticles, beside for nanoparticle characterization, TEM technique was used to confirm the stability of the nanoparticles after radiolabeling. Furthermore, the porous structure of hybrid silica particles loaded with budesonide was examined under TEM. Transmission electron microscopy technique offers exceptional benefits for nanoparticle characterization. Additionally, the necessity of ultrastructural analysis demonstrates the potential of TEM in the field of nanomedicine. Hence, the long-established and well-known TEM has been only partially exploited and offer researchers very detailed images of specimens at microscopic and nano scale.

Qualitative evaluation of high pH mass spectrometry-compatible reversed phase liquid chromatography for altered selectivity in separations of intact proteins

Intact proteins are increasingly being recognized as potential biomarkers and biotherapeutic agents for cancer and other serious diseases. Low pH reversed phase plays an important role in both single and multidimensional protein separations for resolving complex protein samples prior to mass spectrometric detection. In this work, we evaluated the use of high pH reversed phase liquid chromatography as an alternative chromatographic separation to gain different selectivity while maintaining the high resolving power and MS compatibility of reversed phase separations. The altered selectivity gained by high pH reversed phase liquid chromatography can further help to separate unresolved protein peaks or to increase peak capacity and resolving power of a multidimensional setup for complex biological samples. Hence, we evaluated the use of different MS-friendly buffers, ion pairing reagents, and stationary phases (silica- and polymer-based) at alkaline pH for intact protein separations. The best chromatographic separation, with complementary selectivity to low pH reversed phase, was achieved using triethylammonium bicarbonate at pH 10 and hybrid silica particles.

Molecularly Imprinted Polymer-Silica Hybrid Particles for Biomimetic Recognition of Target Drugs

Biomimetic hybrid particles based on amlodipine-imprinted poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MIP) are developed by free radical polymerization of the monomers and crosslinkers in the presence of silica nanoparticles. Atomic force microscopy is used to study the distribution and surface morphology of MIP-silica hybrid particles. The responsive properties are studied by exposing the synthesized MIP-silica hybrid material to standard amlodipine drug solution and consequently monitoring the decrease in drug concentration. The control material, i.e., nonimprinted polymer- (NIP-) silica hybrid particles, exhibits much lower response during the drug rebinding assay suggesting the lack of functionality due to the absence of imprinting effects. The selectivity of MIP-silica hybrid particles is evaluated by examining the aspirin uptake that shows lower absorbance shifts for aspirin solution compared to amlodipine. It indicates a higher sensitivity of MIP-silica hybrid particles toward targeted pharmaceutical drug recognition and also exhibits their potential for drug assay in multiplex biological samples. Furthermore, MIP-silica hybrid particles used in the drug rebinding assay can be recovered and regenerated for subsequent tests without losing recognition properties.

Improvement in efficiency and stability of quantum dot/polymer nanocomposite film for light-emitting diodes using refractive index-controlled quantum dot–silica hybrid particles

Controlling refractive index of hybrid particles suppressed light scattering and enhanced efficiency and stability of nanocomposite film.

Characterization of the physical–mechanical properties of dental resin composites reinforced with novel micro-nano hybrid silica particles: An optimization study

In the study, dental composites of color A2 using Bis-GMA/UDMA/TEGDMA resins (ratios 70/10/20), and silica filler (70%wt, 75%wt, and 80%wt) which is a hybrid of two silica types in nano and micro dimensions were made using two different photoinitiators namely BAPO and camphorquinone. The optimum photoinitiator was selected based on the mechanical tests results after which the composites were subjected to the following tests: FTIR to evaluate polymerization degree, microhardness test, UTM, and SEM micrographs were taken to analyze the surface fracture of samples. The results of photoinitiator selection (flexural strength test) is 36.54 MPa, 37.62 MPa, and 75.08 MPa for BAPO + camphorquinone, camphorquinone, and BAPO respectively. The results show that the BAPO photoinitiator exhibits better results over camphorquinone and also BAPO/camphorquinone initiator systems. Then after choosing the photoinitiator system composites with different filler contents show higher mechanical strength than existing dental composites. The results of the mechanical tests for the composites with different filler contents synthesized after initiator system selection were significantly higher than the values specified in ISO 4049:2009 (102 MPa over 80 MPa). FTIR results indicate that the degree of conversion in these composite is 25.41%, 37.68, and 40.94% for composites with different filler amounts.

Effects of mixed ultrafine colloidal silica particles on chemical mechanical polishing of sapphire

The effects of ultrafine colloidal silica particles adsorbed on the surfaces of large silica particles in slurries used for the chemical mechanical polishing of sapphire were studied. Sapphire wafers were polished using hybrid silica particles that were composed of a mixture of ultrafine (4 nm) colloidal silica particles and large (20, 55, and 105 nm) silica particles. Dynamic light scattering results showed that the hybrid particles became larger after mixing. Transmission electron microscopy images revealed that the ultrafine particles adhered to the surfaces of the large particles and that the surface shape of the hybrid particles were changed by the mixing process. Atomic force microscopy and polishing results showed that the surface roughnesses and material removal rates of sapphire substrates were improved by using the hybrid particles. The coefficient of friction between the surface of the sapphire substrate and the hybrid particles was higher than that obtained using single-sized particles. These results confirm that the hybrid silica particles enhanced the performance of sapphire polishing.

Selective and Efficient Arsenic Recovery from Water through Quaternary Amino-Functionalized Silica.

The free-radical graft polymerization of acryloxyethyl-trimethylammonium chloride onto commercial silica particles was studied experimentally for extraction of arsenic ions from water. Two steps were used to graft acryloxyethyl-trimethylammonium chloride (Q) onto the surface of nanosilica: anchoring vinyltrimethoxysilane (VTMSO) onto the surface of silica to modify it with double bonds and then grafting Q onto the surface of silica with potassium persulfate as an initiator. The products were characterized by Fourier-transform infrared (FT-IR), the thermogravimetric analysis (TGA), scanning electron microscopy (SEM), 13C, 29Si nuclear magnetic resonance (NMR), and X-ray powder diffraction (XRD). The results showed that it is easy to graft Q onto the surface of silica under radical polimerization. The morphology analysis of silica and modified silica indicated that the silica decreased the size scale after modification. Q/VTMSO-SiO2 was tested for its ability to remove arsenic from drinking water. The results show that the new silica hybrid particles efficiently remove all arsenate ions. In addition, Q/VTMSO-SiO2 showed better sorption capacities for other metal ions (such as copper, zinc, chromium, uranium, vanadium, and lead) than a commercial water filter.

One-pot spontaneous formation of submicron hexane-dispersible silica particles with the aid of amphiphilic reaction solvent

Hydrophobic submicron hybrid silica particles were spontaneously formed in the mixture of tetraethylorthosilicate (TEOS) and hexyltrimethoxysilane (HTMS) dissolved in diethylamine, which works as a catalytic Lewis basic amphiphilic reaction solvent. The obtained hybrid silica particles were stably dispersed in non-polar solvent such as hexane in the form of the primary-particle dispersion. The solvent diethylamine functioned not only as the catalyst for the silanol polycondensation but also as a superior dispersant for the primary-particle dispersion of the hydrophobic hybrid silica particles throughout the formation process. After the addition of TEOS, HTMS and water in diethylamine, the particle nucleation was promoted the ultrasonication for 30 s. Then, the uniform-sized submicron hydrophobic hybrid silica particles were spontaneously formed after the dispersion of the nuclear was kept still for 24 h. The surface of the hybrid silica particles became increasingly hydrophobic. This is because of the higher density of the non-polar pendant groups (hexyl groups) in the vicinity of the surface, which results from the lower reactivity of trifunctional HTMS than that of tetrafunctional TEOS. The merits of using diethylamine are summarized as follows; 1) Since diethylamine strongly catalyzes silanol condensation, the particle surface was thoroughly hydrophobized. 2) Since the hydrophobized particle had good affinity with diethylamine, the hybrid silica particles remained stably dispersed in it. Furthermore, even after the hybrid silica particles are air-dried, they are redispersed in hexane in the form of the primary-particle dispersed.

Microfluidic Examination of the "Hard" Biomolecular Corona Formed on Engineered Particles in Different Biological Milieu.

The formation of a biomolecular corona around engineered particles determines, in large part, their biological behavior in vitro and in vivo. To gain a fundamental understanding of how particle design and the biological milieu influence the formation of the "hard" biomolecular corona, we conduct a series of in vitro studies using microfluidics. This setup allows the generation of a dynamic incubation environment with precise control over the applied flow rate, stream orientation, and channel dimensions, thus allowing accurate control of the fluid flow and the shear applied to the proteins and particles. We used mesoporous silica particles, poly(2-methacryloyloxyethylphosphorylcholine) (PMPC)-coated silica hybrid particles, and PMPC replica particles (obtained by removal of the silica particle templates), representing high-, intermediate-, and low-fouling particle systems, respectively. The protein source used in the experiments was either human serum or human full blood. The effects of flow, particle surface properties, incubation medium, and incubation time on the formation of the biomolecular corona formation are examined. Our data show that protein adhesion on particles is enhanced after incubation in human blood compared to human serum and that dynamic incubation leads to a more complex corona. By varying the incubation time from 2 s to 15 min, we demonstrate that the "hard" biomolecular corona is kinetically subdivided into two phases comprising a tightly bound layer of proteins interacting directly with the particle surface and a loosely associated protein layer. Understanding the influence of particle design parameters and biological factors on the corona composition, as well as its dynamic assembly, may facilitate more accurate prediction of corona formation and therefore assist in the design of advanced drug delivery vehicles.

Biomimetic self-slippery and transferable transparent lubricant-infused functional surfaces.

Self-slippery liquid-infused porous surfaces (SLIPSs) have been presented owing to their enormous number of potential applications and have widely attracted the attention of researchers in recent years. In comparison with superhydrophobic surfaces, SLIPSs not only exhibit interfacial performance that corresponds to superhydrophobicity but also do not require the construction of a complicated and delicate morphology. Here, a facile strategy has been proposed for constructing silica SLIPSs. Three common lubricants (perfluoropolyethers, liquid paraffin and ethyl oleate) were employed in this study. Using a facile brush process, the surface can be coated on a substrate, and, after infusion of the lubricant, the transformation from superhydrophobicity to self-slippage properties can be achieved. In addition, changing the kind of lubricant and adjusting the amount of nanoscale hybrid silica particles in the coating solution can modulate the surface transparency and interfacial characteristics, which makes the surface meet the various requirements of different service conditions. This transferable performance endows the surface with the possibility of meeting the various requirements of different conditions and demonstrates the enormous value of the application of the coatings in many fields.

An All‐in‐One Molecule for the One‐Step Synthesis of Functional Hybrid Silica Particles with Tunable Sizes

Spherical particles with well‐defined diameters were obtained by self‐assembly of trityl‐based molecules. Thanks to the robustness of the organic scaffold, a variety of modifications could be covalently introduced into the network so as to stabilize the supramolecular structure by a sol–gel route. Using supramolecular chemistry, we showed that the synthesis of hybrid small molecules allowed engineering nanomaterials with tunable size and functionality. The use of a combination of different characterization techniques, including dynamic light scattering, cryoTEM, and solid‐state NMR spectroscopy, provided careful understanding of the relationship between the molecular and supramolecular structures for further chemical engineering of supramolecular hybrid materials.