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In this study, thin-film nanocomposite (TFN) membranes were fabricated using synthetic silica nanoparticles that had been aminated by 3-aminopropyltriethoxysilane (APTES). The modified silica nanoparticles with APTES were analyzed using FTIR and TGA. Through the use of FTIR-ATR spectroscopy, FESEM, AFM, and water contact angle, the fabricated TFN membranes were analyzed and evaluated. All membranes were used in a submerged membrane system to remove humic acid (HA) under various transmembrane pressure (TMP) conditions at 0.4 and 0.6 bar. The outcome of the research showed that the polycarbonate (PC) support membrane has a water contact angle of 77.5°; however, the TFN membrane, which includes 0.1 wt.% of hydrophilic modified silica nanoparticles, has a substantially lower contact angle value (55.33°). The formation of a thin layer of polyvinyl alcohol (PVA) on the PC support membrane and the proper distribution of SiO2-NH2 nanoparticles with a thickness of 93.72 nm were confirmed by FESEM images. The rejection rate for thin-film composite (TFC) membranes was about 98.3%, while for TFN membranes, in the presence of SiO2-NH2 nanoparticles, it reached 99.2%. [ABSTRACT FROM AUTHOR]

A multifunctional hybrid curing component (GSD) for epichlorohydrin-modified novolac resin (ENR) was synthesized via grafting poly(amidoamine) (PAMAM)-modified silica nanoparticles (SD) on graphene oxide (GO) using a ring opening reaction. SD and GSD, as two different curing components, were also used in different contents as reinforcing fillers of ENR matrix. Fourier-transform infrared spectroscopy and thermal gravimetric analysis (TGA) results proved amine-decoration of silica nanoparticles and also successful preparation of GSD. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy results were utilized to investigate structure of the SD and GSD multifunctional curing components and also the resulted composites. XRD pattern of GSD shows two peaks at 10.1 and 21.8° which belong to characteristic peaks of GO and silica nanoparticles, respectively, with weak intensities due to grafting of SD on the GO surface. Thermal investigation of the prepared composites by TGA showed that curing ENR with higher contents of GSD was resulted in higher thermal properties. The ENR composite cured with 5 wt% of GSD presented the highest char residue of 20.5% among the other hybrid composites. [ABSTRACT FROM AUTHOR]

A hyperbranched hybrid curing agent (CSD) for epoxidized novolac resin (ENR) was prepared by grafting silica nanoparticles modified with poly(amidoamine) (PAMAM) dendritic structure (SD) to carbon nanotube (CNT) using an esterification reaction between the amino functional groups of SD and carboxylic acid functionalities of oxidized CNT. ENR was prepared by a reaction between novolac resin and epichlorohydrin. Curing of ENR was carried out with two different contents of CSD as the hyperbranched hybrid curing component of the epoxidized matrix. The amino-rich structure of CSD could result in its high dispersion in the ENR matrix and consequently high thermal stability of the hybrid composites. Fourier-transform infrared spectroscopy and thermal gravimetric analysis (TGA) showed successful modification of silica nanoparticles and CNT with the PAMAM dendritic structure and SD, respectively. Structure of the resulting hybrid curing agents (SD and CSD) was investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Thermal investigation of the resulted composites by TGA showed that the cured ENR with higher content of CSD has high thermal properties with a char residue of 44.4% among the other hybrid composites. [ABSTRACT FROM AUTHOR]

Effect of different chain extenders, silica nanoparticle loading, and using sol-gel method on the thermal properties of polyurethane (PU) hybrid composites was investigated from the viewpoint of increase of char residue and decomposition temperature. Two different chain extenders were used for this purpose, and the PU products were modified with (3-aminopropyl) triethoxysilane to obtain PUI (ethoxysilane-terminated PU with pyromellitic dianhydride chain extender) and PUBD (ethoxysilane-terminated PU with butanediol chain extender), respectively. Fourier-transform infrared spectroscopy was used for confirmation of synthesis of PUI and PUBD. Thermogravimetric analysis showed that char residue and thermal degradation temperature of PU hybrid composites were increased after incorporation of silica nanoparticles. Also, using pyromellitic dianhydride as chain extender resulted in higher char contents and also thermal stabilities in comparison with butanediol. By the addition of 4 and 8 mass% silica nanoparticles in PUBD hybrids, char residue increased to 15.1 and 16.3%, respectively. In the case of PUI hybrids, addition of 4 and 8 mass% of silica nanoparticles resulted in char residue of 20.8 and 25.7% and Tmax of 409.3 and 411.8 °C, respectively. X-ray diffraction showed an amorphous peak for cross-linked PU at 2θ = 21.7°. Transmission electron microscopy showed dispersion of silica nanoparticles in the hybrid composite of PUI. [ABSTRACT FROM AUTHOR]

A facile method was developed for preparation of three hybrid composites by using tetraethyl orthosilicate oligomer‐modified epoxy resin (MER), (3‐glycidyloxypropyl) trimethoxysilane‐modified novolac resin (MNR), epoxidized novolac resin (ENR), and silica nanoparticles (SiO2). Accordingly, the first class of composites was prepared from MER and SiO2. The second class of composites was prepared from MER, MNR, and SiO2. And the third class of composites was prepared from silica MNR, ENR, and nanoparticles. All the modified resins and their composites were characterized by Fourier‐transform infrared spectroscopy and their thermal behavior was investigated by thermo gravimetric analysis. The obtained thermograms showed that thermal stability of hybrid composites were controlled by the amount of SiO2 and type of resins. Char yield of epoxy resin was increased significantly by formation of hybrid composites. The second class of composites showed higher char yields in comparison with the first class (52.1 compared with 23.2% for 8 wt% of SiO2). Incorporation of ENR instead of MER in the third class composites resulted in much more char residues of 60.2 and 60.6% for 4 and 8 wt% of SiO2. Therefore, third class composite with 8 wt% of SiO2 exhibited the highest char yield. Scanning electron and transmission electron microscopies were used to study the morphology and dimension of SiO2. POLYM. COMPOS., 39:E2316–E2323, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

This work presents a unique desymmetrization method to produce a high quantity of Janus nanoparticles (JNPs) using dual-phase oil (melted wax)/water system. The four-stage process includes fixing, primary modification, releasing, and secondary modification. Unlike other works, dispersed hydrophilic nanoparticles were forced to be placed at oil/water interface using an upward water stream formed by buoyancy effects due to the applied heat to the bottom of the container. This eliminated some significant deficiencies of common desymmetrization processes which apply oil (melted wax)/water Pickering emulsion systems, e.g., the coalescence of melted /solidified wax droplets and high cost. The best effect of heat-driven buoyancy flow was ensured using saturation theory. In order to induce asymmetrical surface properties to the applied nanoparticles, (3-aminopropyl)triethoxysilane and hexadecyltrimethoxysilane were used in primary and secondary modification stages, respectively. Produced JNPs were characterized using FTIR, thermogravimetric analysis (TGA), and energy-dispersive X-ray spectroscopy (EDX) tests in order to confirm the attachment of modifier molecules on the surface of the applied nanoparticles. Furthermore, TGA results were used to calculate three-phase contact angle ( β) as an important parameter dictating the asymmetric properties of Janus nanoparticles. Also, a dichloromethane/water mixture was used to demonstrate the differences of Janus nanoparticles with similar uniformly modified nanoparticles. Furthermore, using polystyrene/poly(methyl methacrylate) blend, it was shown that produced Janus nanoparticles tend to be placed at the interface while their corresponding uniformly modified nanoparticles stay in polystyrene or poly(methyl methacrylate) phase. [ABSTRACT FROM AUTHOR]

This work presents a unique method to produce large amounts of very small Janus nanoparticles (<50 nm) using Pickering emulsions of paraffin-in-water, known as desymmetrization process in high internal interface systems. Unlike other similar works, applying a thermal shock in cooling stage allowed surfactants to be not used in the process besides stabilizing nanoparticles. This provided better modification efficiency after coverage of solid paraffin droplets with small nanoparticles as well as controlling limited and partial coalescences. Two types of silica nanoparticles with different size (<50 nm) were used and (3-aminopropyl)triethoxysilane was also applied in order to modify their exposed surface after preparation of stabilized emulsion. Besides SEM images, some other new experimental/analytical procedures are proposed in order to investigate the presence of nanoparticles on the surface of provided solid paraffin droplets. Produced Janus nanoparticles were characterized using FTIR, TGA and EDX tests in order to confirm the chemical modification. Furthermore, a chloroform/water mixture was used to demonstrate the differences of Janus nanoparticles with similar uniformly modified nanoparticles. The results revealed the amphiphilic properties of Janus nanoparticles which led them to be placed at the interface while uniformly modified particles were placed in chloroform phase. [ABSTRACT FROM AUTHOR]

A facile and effective approach was developed to fabricate dual temperature- and pH-sensitive hollow nanospheres utilizing an atom transfer radical polymerization (ATRP) method. To do this silica nanoparticles were used as primary cores that could be etched by an hydrofluoric (HF) aqueous solution. Due to uncontrolled ATRP of acrylic acid (AA) methyl acrylate (MA) was polymerized via surface-initiated ATRP (SI-ATRP) a and poly(2-hydroxyethyl methacrylate) (PHEMA) block was added via the same approach. To synthesize poly(AA- co-HEMA)-grafted silica nanoparticles polymethyl acrylate (PMA) chains were hydrolyzed to polyacrylic acid (PAA) using an aqueous NaOH solution. PAA segments were partially crosslinked via an esterification reaction of -COOH groups with 1,4-butanediol. Finally, poly(AA- co-HEMA) hollow nanospheres were fabricated by etching silica cores with an HF aqueous solution. The structure of the nanospheres was revealed by transmission electron microscopy (TEM). These hollow nanospheres consisting of poly(AA- co-HEMA) in their structure showed dual pH- and thermo-sensitive properties as measured by dynamic light scattering (DLS). The hydrodynamic diameter was measured as an affected parameter under different pH (3-12) and temperature (25-55 °C) conditions. Results showed that by decreasing pH or by increasing temperature the hydrodynamic diameter decreased and a lower critical solution temperature (LCST) point was observed. [ABSTRACT FROM AUTHOR]

Nanoporous silica aerogel particles were synthesizedviasol–gel process and modified with a hydrophobic surfactant. Batch polymerizations of styrene in presence of silica aerogel particles were studiedviafree radical and reversible addition–fragmentation chain transfer (RAFT) polymerizations. Monomer conversion, molecular weight, and polydispersity index of each system were monitored during polymerization to investigate the reaction kinetics. According to results, in both systems, the presence of silica aerogel particles has a sensible influence on polymerization kinetic and adding aerogels results in decreased polymerization rate, conversion, and molecular weight. Moreover, the prepared samples were characterized by Fourier transform infrared spectroscopy. Also, thermal gravimetric analysis (TGA) and differential scanning calorimetric techniques was used to observe the effect of aerogel particles on thermal properties of synthesized nanocomposites. According to TGA depiction, in free radical samples, one-stage degradation, related to random chain scission, is observed while degradation of RAFT-prepared nanocomposites occurred in two steps due to the decomposition of RAFT moieties and random chain scission. [ABSTRACT FROM PUBLISHER]

A number of batch polymerizations were performed to study the effect of pristine nanoparticle loading on the properties of PMMA/silica nanocomposites. In order to improve the dispersion of silica nanoparticles in the PMMA matrix, the silanol groups of the silica are functionalized with methacrylate groups and modified nanoparticles were used to synthesize PMMA/modified silica nanocomposites. Prepared samples were characterized by thermogravimetric analysis (TGA), dynamic light scattering (DLS), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). According to the results, introduction of modified nanoparticles results in better thermal and mechanical properties than those of pristine nanoparticles. Also, surface modification and increasing silica nanoparticles result in variation of thermal degradation behavior of nanocomposites. The best improvement of the mechanical and thermophysical properties is achieved for nanocomposites containing 7 wt.% silica nanoparticles. [ABSTRACT FROM PUBLISHER]

Abstract: To study the effect of silica nanoparticles on the kinetics of methyl methacrylate free radical polymerization, a number of batch polymerizations were performed using pristine and methacrylate-modified silica nanoparticles at 75°C. In addition, effect of temperature was investigated on the kinetics of polymerization with 1wt% loading of pristine nanoparticles. Monomer conversion, reaction rate, molecular weight and polydispersity index (PDI) of each polymerization were monitored during polymerization. According to results, no considerable change was obtained on the polymerization kinetics by introduction of any type of nanoparticles, while there is an optimum loading value in which the polymerization rate reaches its maximum level. A similar trend is observed for molecular weight of free chains; however, increasing silica content results in increased PDI values. Also, polymerizations rate is slower for batches containing modified nanoparticles. For chains which are grafted on the surface of modified nanoparticles, molecular weight and PDI values increase by increasing nanoparticle content. [Copyright &y& Elsevier]

In this study, hybrid composites of polyurethane-acrylate (PUA) and silica nanoparticle were prepared by a radical method. For this aim, silica nanoparticles were chemically functionalized with 3-methacryloxypropyltrimethoxysilane. Polyurethane was synthesized and then modified with 2-hydroxyethyl methacrylate to yield PUA. Then, different amounts of modified-silica were used to prepare PUA composites by the addition of an ethylene glycol dimethacrylate crosslinker. Fourier-transform infrared spectroscopy confirmed the successful functionalization of silica nanoparticles and the preparation of PUA. Structural investigation of the functionalized-nanoparticles and also nanocomposites was carried out using X-ray diffraction and electron microscopy. According to the thermal gravimetric analysis results, char residue of HSiO 2 is 86.6%, which decreases to 81.3% in the case of MSiO 2 as a result of its modifier degradation content of 5.3%. PUAS5 shows main decomposition temperatures of 396.5 and 454.9 ∘ C and also char content of 5.7% at 700 ∘ C . The high amount of MSiO 2 can also be resulted in higher degree of crosslinking and therefore higher thermal stabilities and char residue. [ABSTRACT FROM AUTHOR]

Smart drug-delivery systems based on stimuli-responsive polymers are extensively studied because of their advantages in controlled release of anti-cancer drugs in response to induced stimuli. To develop a smart drug-delivery system, silica nanoparticles modified with 3-(trimethoxysilyl) propyl methacrylate (MPS) were used in inverse emulsion polymerization of N , N -dimethylaminoethyl methacrylate with N , N -methylene bisacrylamide in different amounts (MBA: 2, 4, and 8 mol%). The temperature- and pH-responsive hybrid core-shell nanoparticles were used for preparation of hollow poly(N , N -dimethylaminoethyl methacrylate) (PDMAEMA) nanogels by hydrolysis of the silica cores. Fourier-transform infrared spectroscopy was used to confirm the surface modification of silica nanoparticles with MPS. Successful synthesis of the hybrid and hollow nanogels was investigated by thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. In addition, temperature-responsivity and phase separation behavior of the hybrid and hollow nanogels were studied by UV/Vis spectroscopy. The UV/Vis spectra showed that the absorption intensity was increased with increasing MPS and MBA contents in basic conditions. The hollow nanogels showed higher swelling/deswelling ratio compared to the hybrid nanogels in acidic media (pH 3.5) and at temperatures above the volume phase transition temperature (70 °C). Some of the hybrid and hollow nanogels with different crosslinking densities were used as smart drug carriers for doxorubicin (DOX), and their release behavior were investigated at different pH (3.5 and 7.5) by UV/Vis spectroscopy. The release profiles display that release of DOX has increased in pH of 3.5, and the hollow nanogels showed lower release contents than the hybrid nanogels because of diffusion and encapsulation of DOX molecules in the hollow space. The experimental release profiles confirmed that DOX release percentage in the hybrid nanogels was more than the hollow ones, while loading capacity of the hollow nanogels was higher. The Korsmeyer-Peppas model showed the best fitting with the experimental results of DOX release from PDMAEMA carriers. Image 1 • Temperature- and pH-responsive hybrid and hollow nanogels were prepared by inverse emulsion polymerization. • The hybrid and hollow PDMAEMA nanogels were prepared in different crosslinking densities. • The hybrid and hollow nanogels were used as doxorubicin carriers. • Release of doxorubicin has been increased at temperatures below the lower critical solution temperature of PDMAEMA and also in acidic conditions. • Hollow nanogels showed higher loading capacity and lower release contents (percentage) than the hybrid nanogels. [ABSTRACT FROM AUTHOR]