Surface-modified Silica Nanoparticles Research Articles

Investigating the effect of surface composition and morphology on oil/water separation efficiency of sponges coated with polymer nanocomposites

As a worldwide challenge, the oil spillage has gained tremendous attention within the last few years. In this work, a facile method is proposed to fabricate sponges treated with polydimethylsiloxane (PDMS) and modified/unmodified silica nanoparticles exhibiting superhydrophobic and superoleophilic properties for enhanced oil/water separation. The main aim is to delineate the role of surface composition versus surface morphology by employing different formulations. Scanning electron microscopy results demonstrated that a rough structure, induced by formation of a packed assembly of nanoparticles, gives a major contribution to the obtained superhydrophobic behavior. It was also proved that the surface modification of silica nanoparticles might play an even more important role in attaining superhydrophobicity. Once a combination of PDMS and modified silica was used, different oil/water mixtures were efficiently separated. On the other hand, surface composition of the coating was found to be the major factor affecting wettability of sponges and their capability to separate water/oil mixtures. Therefore, results of this study can be used as a hint for designing more efficient sponge‐based systems modified with polymer nanocomposites for oil/water separation applications. POLYM. COMPOS., 40:E431–E439, 2019. © 2018 Society of Plastics Engineers

Preparation of Surface Modified Silica nanoparticles with Silane Coupling Agent in Supercritical Carbon Dioxide

Preparation of Surface Modified Silica nanoparticles with Silane Coupling Agent in Supercritical Carbon Dioxide

Effect of surface modification of silica nanoparticles by silane coupling agent on decontamination foam stability

The effect of surface modification of silica nanoparticles by Dimethyldichlorosilane (DMDCS) on decontamination foam stability was investigated by the measurement of decaying foam volume with time using a Foamscan. The hydrophobicity of silica nanoparticles modified by DMDCS was characterized by active ratio via a floating test and contact angle analysis. Contact angle measurement has shown that silica nanoparticles surface become more hydrophobic as DMDCS concentration increases. Foam stability test in unmodified silica particles-surfactant mixtures revealed that silica nanoparticles-surfactant stabilized foams are much more stable than surfactant-stabilized foams and certain level of surfactant concentration is required for the synergy between silica nanoparticle and surfactant. In foam stability test with modified silica particle-surfactant mixtures, it was found that silica nanoparticles with the proper level of hydrophobicity shows the best performance in foam stability and this result was supported by optical and fluorescence microscope images.

A micromechanical study on the existence of the interphase layer in particle-reinforced nanocomposites

In this paper, the effective elastic properties of nanoparticles reinforced nanocomposites including effects of an interphase layer around the nanoparticles are determined using analytical micromechanical approach. The present micromechanical model is based on the Green’s function and the interface operator. By using the interface operator, the interphase layer and the nanoparticle are combined as a single spherical inclusion and then the effective properties of the composite are calculated by using the Green’s function. To assess the presented method, epoxy-silica nanocomposites are thoroughly studied in this paper. Since there is no direct method to determine physical and mechanical properties of the interphase layer, we have presented a method to determine these properties, namely volume fraction and elastic modulus of the interphase layer, for epoxy-silica nanocomposites by correlating the experimental data for effective elastic properties of the epoxy-silica nanocomposites and those obtained by the presented model. Applying the presented method to various experimental data available in the literature, epoxy-silica nanocomposites are characterized into nanocomposites with, and without an interphase layer. The presence or absence of the interphase layer is concluded by the value of its volume fraction determined by the present method. It is observed that nanocomposites with surface-modified silica nanoparticles yield perfect bonding with the matrix and do not form an interphase layer. On the other hand, nanocomposites with raw silica nanoparticles (without surface modification) yield an interphase layer between the nanoparticles and the matrix which is softer than the matrix.

Preparation of UV-cured spironaphthooxazine/silica/polyacrylate photochromic hard coatings on plastic substrates

Hard coatings exhibiting photochromic properties were prepared by UV-curing of formulations that incorporated surface-modified silica nanoparticles, hexa-functional curing agent, and organic dye (spironaphthooxazine) on poly(methyl methacrylate) (PMMA) substrates. Spectroscopic studies of the coatings indicated effective photochromic activities over the visible range in response to UV irradiation (365 nm). The color density and bleaching performance were found to depend on the silica and dye contents in the coatings; generally, increasing either quantity could increase the color density and raise the initial bleaching rate, and yet it took a longer time to completely bleach the coatings. Furthermore, the coatings were very hard (8H), attached perfectly (5B) on the substrate, and were much more wear-resistant than pure PMMA against the CS-10 abradant.

A simple and environment-friendly approach for synthesizing macroporous polymers from aqueous foams

We propose a facile and environment-friendly approach for the preparation of macroporous polyacrylamide (PAM) via thermal-initiated polymerization of aqueous foams that are stabilized by surface-modified silica nanoparticles. Cetyltrimethylammonium bromide (CTAB) is used to delicately adjust the surface amphiphilicity of silica to stabilize aqueous foams. The air bubble size and size distribution is affected by the wettability of silica particles, solid content and air volume fraction in the foams. The morphology of macroporous polymers is observed by a scanning electron microscope (SEM). The pore and pore throat size can be tailored effectively by varying the silica content and air volume fraction. A high porosity of 83% is achieved when the air volume fraction of the aqueous foam is 65%. PAM hydrogels obtained via polymerizing aqueous foams show pronounced advantage over the ones prepared from oil-in-water (O/W) emulsions in wastewater treatment because of their unique pore structure. This strategy would also be extended to prepare other macroporous polymers with well-defined pore structures.

Modification of silica nanoparticles with stereisomers of p-tert-butylthiacalix[4]arene containing four 2-oxo-2-{[3-(triethoxysilyl)prop-1-yl]amino}ethoxy substituents at the lower rim

Three stereoisomers (cone, partial cone, and 1,3-alternate) of p-tert-butylthiacalix[4]arene bearing four anchor propyltriethoxysilane substituents at the lower rim were synthesized for the first time. Surface modification of silica nanoparticles (d = 12 nm) with the synthesized macrocycles gave novel hybride thiacalix [4]arene‒SiO2 particles. The obtained nanostructured adsorbents were found to efficiently extract nitroaromatic compounds from aqueous solutions. The partial cone and 1,3-alternate thiacalix[4]arene–SiO2 hybrid particles showed affinity to nitrophenols.

Asymmetric silica composite polymer electrolyte membrane for water management of fuel cells

We prepared an asymmetric composite membrane in which surface modified silica nanoparticles were added to sulfonated poly(arylene ether ketone) (SPAEK). The asymmetric structure, hydrophilic silica to the anode side and hydrophobic silica to the cathode side in the polymer matrix, enhanced the water back diffusion from the cathode to anode within the membrane, which results in an increase of proton conductivity, particularly under low humidity conditions. The improved water back diffusion is attributed to the different water retention character and surface energy gradient of surface modified silica that accelerates water transport. The asymmetric composite membrane exhibited high and stable electrochemical performance of a fuel cell. Analysis of drain water and electrochemical characterization supports the structural effect of the asymmetric composite membrane for efficient water management.

Preparation, characterization and application of dispersible and spherical Nano-SiO2@Copolymer nanocomposite in leather tanning

Dispersible and spherical silica nanoparticles (nano-SiO2) were prepared with tetraethyl silicate and different surface-modifiers via a simple method. The silica nanoparticles surface-modified with methacryloxy (propyl) trimethoxysilane (denoted as MPS-SiO2), dimethyl diallyl ammoniumchloride (denoted as DMDAAC-SiO2) and poly (methacrylic acid) (denoted as PMAA-SiO2) which are known as hydrophobic, amphiphilic and hydrophilic modifiers, respectively, exhibited excellent dispersibility in various solvents or polymer matrix. The obtained bare silica nanoparticles, MPS-SiO2, DMDAAC-SiO2 and PMAA-SiO2 were characterized by Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA), transmission electron microscope (TEM) and scanning electron microscope (SEM). A series of nanocomposites (denoted as SiO2/P, MPS-SiO2/P, DMDAAC-SiO2/P and PMAA-SiO2/P, respectively) were also prepared with the bare or surface-modified silica nanoparticles and methacrylic acid-co-acrylamide-co-acrylonitrile-co-salicylic acid tetrabasic copolymer (denoted as PMAAS) and applied in leather tanning. Compared with those of the leather tanned with the commercial acrylic resin (CHINATAN OM) and pure tetrabasic copolymer tanning agents, the physical and mechanical properties, rheological properties and thermal stabilities of the leather treated with SiO2/P, MPS-SiO2/P, DMDAAC-SiO2/P or PMAA-SiO2/P founded to be improved in a significant way. Moreover, the highest shrinkage temperature of the wet-white sheepskin tanned with PMAA-SiO2/P reached to 76°C and the thickness increase reached to 105%.

Some studies on the surface modification of sol-gel derived hydrophilic Silica nanoparticles

In the present investigation surface modification of silica nanoparticles by alumina was carried out by sol-gel process. Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) confirmed the synthesis of silica and the surface modification as alumina is anchored to silica surface. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) investigations observed that alumina doping affected significantly the morphology, particle size distribution and surface area of the synthesized nanoparticles. From N2 adsorption-desorption isotherms studies it was further noted that alumina doping improved the pore volumes of the synthesized silica nanoparticles and the synthesized silica alumina nanoparticles are mesoporous materials. The hydrophobicity test and thermal stability results confirmed the modification and conversion of silica to hydrophobic materials using alumina.

Heterocyclic Grafting Functionalization of Silica Nanoparticles: Fabrication, Morphological Investigation and Application for PVA Nanocomposites

In this study, Knoevenagel condensation reaction was performed to prepare a new designed silane coupling agent from the reaction of the synthetic 4-H pyran derivative (EA) and 3-isocyanatopropyl triethoxysilane. The surface modification of silica nanoparticles by novel modifier was achieved by sol–gel technology. Also, in the next step, PVA/silica nanocomposites have been fabricated to investigate the chemical and physical properties of the new decorated nanoparticles. The surface modification of silica nanoparticles reduced the aggregation of nanoparticles effectively using newly prepared silane coupling agent and showed the enhanced performance for host matrix. FT-IR analysis demonstrated that the six membered ring moieties have been covalently bonded to the surface of the SiO2 nanoparticles. The PVA/SiO2 nanocomposites including 2, 5, 10 and 15 wt% nano contents have been prepared. Characterization of the prepared samples with FT-IR, field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) confirmed the synthesis of the nanocomposites with good dispersion properties for nanoparticles. The particles size of ornamented nanoparticles in nanocomposites are about 50–60 nm as characterized by FE-SEM and AFM analyses.

On the volume resistivity of silica nanoparticle filled epoxy with different surface modifications

It was found that metallic oxide nanoparticles may positively influence insulation properties of polymers working under high electric field. Herewith, four kinds of surface-modified silica nanoparticles were employed to fabricate epoxy nanocomposites. The surface properties of nanoparticles were characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis and contact angles. The effects of surface modification, filler fraction and test temperature on volume resistivity (ρv) of epoxy nanocomposites were studied. It was found that, at different test temperatures, the long-alkyl-modified nanoparticles resulted in higher ρv values of epoxy and less ρv sensitivity to temperature, compared to the short-alkyl-modified and hydroxyl-modified ones. The surface polarity of nanoparticles was found to correlate with the ρv values well. The surface modification may cause two possible mechanisms that affect the ρv values of the epoxy: (i) to offer the nanoparticles different levels of water absorption; (ii) to change the Maxwell-Wagner-Sillars polarization behaviors of the composites.

Shape-Memory Behavior of Polylactide/Silica Ionic Hybrids

Commercial polylactide (PLA) was converted and endowed with shape-memory properties by synthesizing ionic hybrids based on blends of PLA with imidazolium-terminated PLA and poly[e-caprolactone-co-d,l-lactide] (P[CL-co-LA]) and surface-modified silica nanoparticles. The electrostatic interactions assist with the silica nanoparticle dispersion in the polymer matrix. Since nanoparticle dispersion in polymers is a perennial challenge and has prevented nanocomposites from reaching their full potential in terms of performance we expect this new design will be exploited in other polymers systems to synthesize well-dispersed nanocomposites. Rheological measurements of the ionic hybrids are consistent with the formation of a network. The ionic hybrids are also much more deformable compared to the neat PLA. More importantly, they exhibit shape-memory behavior with fixity ratio Rf ≈ 100% and recovery ratio Rr = 79%, for the blend containing 25 wt % im-PLA and 25 wt % im-P[CL-co-LA] and 5 wt % of SiO2–SO3Na. Dielectr...

Mechanical properties, thermal and crystallization behavior of different surface-modified silica nanoparticle-filled PA66 composites

Abstract In this study, two different surface-modified silica nanoparticles, amino-functionalized nanosilica (ATS) and methyl-functionalized nanosilica (HDS), were separately used as nanofillers to fabricate PA66-based nanocomposites by melt blending. The morphology and interface characteristics of the two nanofillers in the composite system and their influence on the mechanical properties, thermal decomposition behavior, and crystallization behavior of PA66 were investigated. The Avrami and Mo methods were applied to study the non-isothermal crystallization kinetics of the nanocomposites. The results revealed that different surface modifications of silica nanoparticles can produce different influences on the mechanical properties and thermal decomposition behavior of the final nanocomposites. The addition of ATS helps increase the strength and stiffness of PA66/ATS nanocomposites, and in the meantime enhances the thermal stability of PA66. The case of HDS is opposite to that of ATS; however, its incorporation can improve the toughness of the material. In addition, the results also indicate that ATS possesses strong heterogeneous nucleation capability, the introduction of which can accelerate the crystallization rate and increase the crystallization temperature, as well as the degree of crystallinity of PA66, while HDS displays an obvious blocking effect on the crystallization process of PA66.

Communication—Co-Electrodeposition of Ni/SiO2(CH2)3SH Composite: Modified Guglielmi's Model and Mechanism of Nucleation

This work studies the influence of surface modification of silica nanoparticles by mercaptopropyl trimethoxysilane on silica weight percent in Ni coating during electrodeposition. Results showed SiO2(CH2)3SH particles were embedded in the Ni coating up to 11%. Also, modified Guglielmi's model and mechanicsm of nucleation of Ni-SiO2(CH2)3SH composite were studied.

Probing the structural basis and adsorption mechanism of an enzyme on nano-sized protein carriers

Silica nanoparticles (SiNPs) are important nano-sized, solid-state carriers/hosts to load, store, and deliver biological or pharmaceutical cargoes. They are also good potential solid supports to immobilize proteins for fundamental protein structure and dynamics studies. However, precaution is necessary when using SiNPs in these areas because adsorption might alter the activity of the cargoes, especially when enzymes are loaded. Therefore, it becomes important to understand the structural basis of the cargo enzyme activity changes, if there is any. The high complexity and dynamics of the nano-bio interface present many challenges. Reported here is a comprehensive study of the structure, dynamics, and activity of a model enzyme, T4 lysozyme, upon adsorption to a few surface-modified SiNPs using several experimental techniques. Not surprisingly, a significant activity loss on each studied SiNP was found. The structural basis of the activity loss was identified based on results from a unique technique, the Electron Paramagnetic Resonance (EPR) spectroscopy, which probes structural information regardless of the complexity. Several docking models of the enzyme on SiNPs with different surfaces, at different enzyme-to-SiNP ratios are proposed. Interestingly, we found that the adsorbed enzyme can be desorbed via pH adjustment, which highlighted the potential to use SiNPs for enzyme/protein delivery or storage due to the high capacity. In order to use SiNPs as enzyme hosts, minimizing the enzymatic activity loss upon adsorption is needed. Lastly, the work outlined here demonstrate the use of EPR in probing structural information on the complex (inorganic)nano-bio interface.

Effects of Surface Modification of Silica Nanoparticles on the Mechanical Properties of UV-curable Silica/Polyurethane Acrylate Nanocomposite

본 연구에서는 실리카 입자 표면을 (3-trimethoxysilylpropyl)diethylenetriamine(TPDT)로 처리하여 아미노기를 도입한 후, 마이클 부가 반응이 가능한 3-(acryloyloxy)-2-hydroxypropylmethacrylate(AHM)과 반응시켜 자유 라디칼 중합이 가능한 methacrylate기를 도입하였다. 순수 실리카, TPDT 혹은 TPDT/AHM으로 개질된 실리카를 충전제로 사용하여 urethane acrylate계 수지와 광중합법으로 나노복합체를 제조하였다. UV 수지 중합체와 순수 실리카, TPDT로 개질된 실리카 및 TPDT/AHM으로 개질된 실리카를 각각 3.0 wt% 포함하는 나노복합체의 탄성률을 측정한 결과, TPDT/AHM으로 개질된 실리카 나노복합체의 탄성률이 333.1MPa으로 UV 수지 중합체보다 30.8% 증가하였음을 확인하였다.

Dispersion of surface-modified silica nanoparticles in polyamide-imide (PAI) films for enhanced mechanical and thermal properties

Silica nanoparticles modified with aminophenyl group were fabricated through two-step sol–gel process under the weak acidic condition due to fast hydrolysis and condensation rate of 3-aminophenyl trimethoxysilane. The aromatic groups on the surface of silica nanoparticles enhanced their dispersion stability in PAI film, and the amine groups were chemically bound with PAI by opening the cyclic imide through nucleophilic attack on carbonyl groups. The thermal stability and mechanical properties of the silica/PAI nanocomposite films have been improved by increasing the amount of modified silica nanoparticles up to 12 wt.%. Specially elongation showed a significant increase by 42.37%.

Self‐Assembly of Nanofillers in Improving the Performance of Polymer Electrolyte Membrane

SummaryUnderstanding structure‐property relationship between polymer‐nanoparticle interface and the distribution of interfacial region and its properties is crucial in establishing the bulk properties of polymer like mechanical stability and conductivity. In this article we try to draw a comparison of the effect of silica nanoparticles modified with three different modifiers on the properties of oxy‐polybenzimidazole (OPBI) to understand the role played by the chemical structure of the organic modifying molecule. We highlight how small changes in the structure of the chosen molecule can bring about substantial improvements in polymer nanocomposites owing to the self‐assembly of nanofillers. We use aminopropyltriethoxysilane (AMS), N‐(3‐trimethoxysilylpropyl) diethylenetriamine (LAMS) and ionic liquid modified silica (ILMS) for the surface modification of silica nanoparticles. The extent of interfacial interaction between each of these silica nanoparticles with OPBI matrix was found to be in the order OPBI/AMS < OPBI/LAMS < OPBI/ILMS. The increased interaction from AMS to LAMS to ILMS manifests as stronger adhesion between the polymer and the nanofiller particles that reflects in three important properties i.e storage modulus, acid doping level and proton conductivity of the nanocomposite membranes. Using TEM microscopy we demonstrate the distinct morphological changes induced by the self‐assembly of differently modified silica nanoparticles and correlate the morphological features to the observed properties. This systematic study represents a significant step towards predicting desired/undesired nanocomposite properties.

Silica/Polyurea Composite: Preparation, Characterization and Study of Dielectric Constant

Silica/polyurea composite was prepared after surface modification of silica nanoparticles. Silica/polyurea composite was characterized by Fourier-transform infrared spectroscopy, ultraviolet spectroscopy, X-ray diffraction and transmission electron microscopy. The results indicate that the helical polyurea has been successfully grafted onto the surfaces of the modified silica. Silica/polyurea composite exhibits clearly core–shell structure. The ultraviolet absorption and crystallizability of silica/polyurea are changed due to the shell of helical polyurea, which possesses regular singlehanded conformation and interchain hydrogen bonds. The dielectric constant of silica/polyurea was also investigated. The result indicates that the interfacial interactions between organic shell and inorganic core increase the dielectric constant value being increased to 6.42 for silica/polyurea. The interchain hydrogen bonds of helical polyurea could also be the reason for the increasing of dielectric constant.