Incorporating Silica Particles Research Articles

Effect of in-situ Incorporated Silica Particles on Properties of Polyurethane Elastomer

Effect of in-situ Incorporated Silica Particles on Properties of Polyurethane Elastomer

Improving the adhesion, flexibility, and hemostatic efficacy of a sprayable polymer blend surgical sealant by incorporating silica particles

Commercially available surgical sealants for internal use either lack sufficient adhesion or produce cytotoxicity. This work describes a surgical sealant based on a polymer blend of poly(lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) that increases wet tissue adherence by incorporation of nano-to-microscale silica particles, without significantly affecting cell viability, biodegradation rate, or local inflammation. In functional studies, PLGA/PEG/silica composite sealants produce intestinal burst pressures that are comparable to cyanoacrylate glue (160 mmHg), ∼2 times greater than the non-composite sealant (59 mmHg), and ∼3 times greater than fibrin glue (49 mmHg). The addition of silica to PLGA/PEG is compatible with a sprayable in situ deposition method called solution blow spinning and decreases coagulation time in vitro and in vivo. These improvements are biocompatible and cause minimal additional inflammation, demonstrating the potential of a simple composite design to increase adhesion to wet tissue through physical, noncovalent mechanisms and enable use in procedures requiring simultaneous occlusion and hemostasis. Statement of SignificanceIncorporating silica particles increases the tissue adhesion of a polymer blend surgical sealant. The particles enable interfacial physical bonding with tissue and enhance the flexibility of the bulk of the sealant, without significantly affecting cytotoxicity, inflammation, or biodegradation. These studies also demonstrate how silica particles decrease blood coagulation time.This surgical sealant improves upon conventional devices because it can be easily deposited with accuracy directly onto the surgical site as a solid polymer fiber mat. The deposition method, solution blow spinning, allows for high loading in the composite fibers, which are sprayed from a polymer blend solution containing suspended silica particles. These findings could easily be translated to other implantable or wearable devices due to the versatility of silica particles.

CO2-Philic [EMIM][Tf2N] Modified Silica in Mixed Matrix Membrane for High Performance CO2/CH4 Separation

Separation of carbon dioxide (CO2) from methane (CH4) using polymeric membranes is limited by trade-off between permeability and selectivity as depicted in Robeson curve. To overcome this challenge, this study develops membranes by incorporating silica particles (Si) modified with [EMIM][Tf2N] ionic liquid (IL) at different IL:Si ratio to achieve desirable membrane properties and gas separation performance. Results show that the IL:Si particle has been successfully prepared, indicated by the presence of fluorine and nitrogen elements, as observed via Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectrometer (XPS). Incorporation of the modified particles into membrane has given prominent effects on morphology and polymer chain flexibility. The mixed matrix membrane (MMM) cross-section morphology turns rougher in the presence of IL:Si during fracture due to higher loadings of silica particles and IL. Furthermore, the MMM becomes more flexible with IL presence due to IL-induced plasticization, independent of IL:Si ratio. The MMM with low IL content possesses CO2 permeance of 34.60 ± 0.26 GPU with CO2/CH4 selectivity of 85.10, which is far superior to a pure polycarbonate (PC) and PC-Sil membranes at 2 bar, which surpasses the Robeson Upper Bound. This higher CO2 selectivity is due to the presences of CO2-philic IL within the MMM system.

Structure—Functional property relationship of aliphatic polyurethane-silica hybrid films

The novel aliphatic polyurethane-silica hybrid films were prepared using prepolymerization method in the presence of spherical, submicron amorphous SiO2 Sidistar T120 particles (0, 1, 2, 5 and 10 wt%). The study of the influence of silica distribution on the structure–functional property relationship of polyurethane (PU) composites was performed using FT-IR, SEM, AFM, TGA, DSC, DMTA, tensile testing and immersion test. It was found that the presence of low SiO2 content is acting as dispersing agent between soft- and hard-segments. Achieved uniform distribution of 1 and 2 wt% of silica caused the formation of additional hydrogen bonds between organic matrix and inorganic filler, and remarkably improved thermal stability, thermal and mechanical properties of obtained polyurethane composites. The agglomerates, formed at higher SiO2 loading (5 and 10 wt%), caused the change of thermal degradation mechanism as well as the change of physical crosslinking disruption mechanism. Despite significantly deteriorated mechanical properties of polyurethanes with heterogeneously incorporated silica particles, the onset temperature of elastomers and the starting of melting of hard domains were registered at higher temperature compared to pure PU. Optimal thermal characteristics (onset, decomposition and melting temperatures) and remarkable tensile properties (especially high elongation-at-break and tensile strength, and extraordinary energy-to-break) compared to pure polyurethane have been determined for the polycarbonate-based polyurethanes containing 1 wt% and especially 2 wt% of SiO2. It allows them to be utilized as mechanically strong and durable coatings or films in biomedical applications or as packaging materials. The solvent-resistance data are well described using novel proposed model covering two swelling and dissolution phenomena. The presence of silica decreased the rate and the amount of swelling in water, acetone, toluene and hexane. The rate and mass reduction of swollen sample in acetone, toluene and hexane also decreased by the addition of SiO2 particles.

Nanobead-on-string composites for tendon tissue engineering.

Tissue engineering holds great potential in the production of functional substitutes to restore, maintain or improve the functionality in defective or lost tissues. So far, a great variety of techniques and approaches for fabrication of scaffolds have been developed and evaluated, allowing researchers to tailor precisely the morphological, chemical and mechanical features of the final constructs. Electrospinning of biocompatible and biodegradable polymers is a popular method for producing homogeneous nanofibrous structures, which might reproduce the nanosized organization of the tendons. Moreover, composite scaffolds obtained by incorporating nanoparticles within electrospun fibers have been lately explored in order to enhance the properties and the functionalities of the pristine polymeric constructs. The present study is focused on the design and fabrication of biocompatible electrospun nanocomposite fibrous scaffolds for tendon regeneration. A mixture of poly(amide 6) and poly(caprolactone) is electrospun to generate constructs with mechanical properties comparable to that of native tendons. To improve the biological activity of the constructs and modify their topography, wettability, stiffness and degradation rate, we incorporated silica particles into the electrospun substrates. The use of nanosize silica particles enables us to form bead-on-fiber topography, allowing the better exposure of ceramic particles to better profit their beneficial characteristics. In vitro biocompatibility studies using L929 fibroblasts demonstrated that the presence of 20 wt% of silica nanoparticles in the engineered scaffolds enhanced cell spreading and proliferation as well as extracellular matrix deposition. The results reveal that the electrospun nanocomposite scaffold represents an interesting candidate for tendon tissue engineering.

Omega-3 PUFA concentration by a novel PVDF nano-composite membrane filled with nano-porous silica particles.

The concentration of omega-3 polyunsaturated fatty acids (PUFA) is important in the oil industries. While the current methods demand high energy consumptions in concentrating the omega-3, membrane separation technology offers noticeable advantages in producing pure omega-3 PUFA. Moreover, concentrating omega-3 via membrane separation produces products in the triacylglycerol form which possess better oxidative stability. In this work, the detailed mechanisms of fouling which limits the performance of membrane separation were investigated. Incorporating silica particles to polymeric membrane resulted in the formation of mixed matrix membrane with improved anti-fouling behaviour compared to the neat polymeric membrane. Hence, the industrial potential of membrane processing to concentrate omega-3 fatty acids is enhanced.

Polyurethane foam/silica chemical hybrids for shape memory effects

Abstract

Waterborne polyurethane nanocomposites having shape memory effects

AbstractUV curable waterborne polyurethane/silica nanocomposites were designed and synthesized with functionalized silicas, where the functionalization was made with allyl isocyanate. The incorporated silica particles gave triple effects of multifunctional chemical cross‐links, reinforcing fillers, and stress relaxation retarders. Consequently, functionalized silica incorporated into the polymer chains showed significantly improved mechanical and thermal properties than the simple addition of unmodified silica. Notably, over 99% shape fixity and shape recovery with minimum cyclic hysteresis were obtained for the repeated cycles at 1% loading of the modified silica. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Thermal stability and flame retardancy of polyester, cotton, and relative blend textile fabrics subjected to sol–gel treatments

AbstractPolyester (PET), cotton (COT), and two relative blend textile fabrics were treated by sol–gel processes. Tetraethoxysilane (TEOS) was used as inorganic precursor of silica phases; furthermore, different TEOS/H2O ratios were examined to explore the effect of the presence of SiO2 on the thermal and fire stability of the textile fabrics investigated. The distribution and dispersion of SiO2 were observed by means of scanning electronic microscopy (SEM). SEM magnifications showed the formation of a continuous silica film located in the neighboring fibers; furthermore, in the case of PET, such a film incorporated silica particles with an average diameter ranging between 0.2 and 6 μm. The thermal and thermooxidative stabilities of the treated samples were investigated by thermogravimetric analysis: after the sol–gel treatment, the degradation mechanism was modified both in nitrogen and in air, and the improvement in the thermal stability was attributed to the presence of silica, which played a protective role in the degradation of the textile fabrics. Finally, we investigated the combustion behavior of the textile fabrics by cone calorimetry, measuring the time to ignition, the heat release rate, and the relative peak. The former was found to depend on the type of fabric; the latter generally evidenced a remarkable decrease for all of the treated samples, up to 35% compared to the neat counterparts. This indicated that the sol–gel treatments improved the flame retardancy of the PET/COT fabrics. This conclusion was also confirmed by limiting oxygen index tests, which evidenced burning kinetics changes in the presence of the silica coating. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Bio-inspired fabrication of composite membranes with ultrathin polymer–silica nanohybrid skin layer

An innovative approach was developed to fabricate composite membranes with ultrathin polymer–inorganic nanohybrid skin layer. The in situ formation of silica nanoparticles within the bulk polymer (poly(vinyl alcohol)) was enabled by the templating and catalysis of inorganic-precipitating polymer (protamine), and the size, morphology as well as spatial distribution of silica nanoparticles were conveniently controlled by the confined space constructed from the cross-linked PVA network. The silica nanoparticle size varied from 14.3 to 8.0 nm by altering the annealing temperature of the cross-linked PVA membranes from 293 to 373 K. Incorporating silica particles destroyed the crystallinity, decreased the glass transition temperature ( T g) and increased the fractional free volume of the nanohybrid skin layer. The sorption experiment indicated the preferential sorption of the nanohybrid films toward water, and the water sorption increased only slightly as the silica content increasing. After the PVA–silica nanohybrid was fabricated into ultrathin skin layer on the polysulfone (PSF) hollow fiber support layer, the PVA–silica/PSF composite membrane exhibited the highest permeance of 8.99 × 10 −9 m 3 (STP)/m 2 s Pa and an infinite separation factor (larger than 2 × 10 6) for 0.3 wt.% water in propylene gas feed at 298 K, when the silica content was 3.4 wt.%.

Shape memory polyurethanes cross-linked by surface modified silica particles

Thermoresponsive polyurethane (PU)–silica nanocomposites were synthesized by incorporating silica particles as multifunctional cross-linkers into the PUvia sol–gel reactions. At 2 wt% silica, the composites showed over 99% shape fixity and shape recovery up to the 4th thermomechanical cycle along with outstanding mechanical properties in their rubbery as well as glass state. The incorporated nano-sized silica particles gave dual effects of multifunctional chemical cross-links and reinforcing fillers. The properties were favorably compared with those of uncross-linked PU and conventionally cross-linked PU.

Organic base‐catalyzed sol–gel route to prepare PMMA–silica hybrid materials

AbstractA series of sol–gel‐derived organic–inorganic hybrid materials that comprise organic poly(methyl methacrylate) (PMMA) and inorganic silica (SiO2) was successfully prepared using aniline as an organic base catalyst to catalyze the sol–gel reactions of tetraethylorthosilicate (TEOS). Aniline was adopted not only as a catalyst but also as a dispersing agent during the preparation of the hybrid materials. The as‐prepared hybrid materials were then characterized using transmission electron microscopy, SEM/energy dispersive X‐ray spectroscopy and Fourier transform infrared spectroscopy. The characteristic temperatures (including Td and Tg) of the hybrid materials slightly exceeded those of neat PMMA, as revealed from thermogravimetric analysis and differential scanning calorimetry evaluations. Studies of the protection against corrosion demonstrated that the hybrid coatings all improved the protection performance on cold‐rolled steel coupons relative to that of neat PMMA coatings, according to measurements of electrochemical corrosion parameters. Additionally, incorporating silica particles into the polymer may effectively reduce the gas permeability of the polymer membrane. Reducing the size of silica particles (at the same silica feeding) further improved the gas barrier property. Optical clarity studies indicated that introducing silica particles into the PMMA matrix may slightly reduce the optical clarity of the films/membranes, as determined by UV‐visible transmission spectroscopy. The contact angle of H2O of the hybrid films increased with the amount of aniline. Copyright © 2006 Society of Chemical Industry Society of Chemical Industry

Metal and Semiconductor Nanowire Network Thin Films with Hierarchical Pore Structures

Metal and semiconductor nanowire thin films with hierarchical pore structure were electrodeposited using mesoporous silica (primary porogens) containing colloidal silica particles (secondary porogens) as templates. The pore size of the nanowire thin films was independently controlled by the wall thickness of the surfactant-templated mesopores and the sizes of the incorporated silica particles. The mesostructure of the nanowire thin films (e.g., hexagonal and cubic mesostructures) was controlled by judicious choice of surfactant. Furthermore, the shape of the secondary pores (e.g., sphere and rod shapes) can be controlled using secondary porogens with various shapes. Such hierarchical nanowire thin films provide novel platforms for photovoltaic, sensor, and other device applications. To demonstrate the advantage of such hierarchical porous networks, we fabricated photovoltaic devices by infiltrating the hole-conducting poly(3-hexylthiophene) into the electron-conducting CdSe nanowire thin films with and without the secondary pore channels. The heterojunction solar cells consisting of a CdSe nanowire network with secondary pore structure and poly(3-hexylthiophene) showed improved performance with a short-circuit current of 2.4 mA/cm2 under AM 1.5 solar illumination, confirming the advantages of such hierarchical pore structure for actual device applications.

Structural reorganization in films of cellulose derivatives in the presence of colloidal particles

Water-cast films of two ethers of cellulose, hydroxypropylcellulose (HPC) and hydroxyethylcellulose (HEC), with dispersed silica particles, were deposited on flat substrates. X-ray specular reflectivity was used to characterize the structure of these solid ca. 1000 Å thick films as a function of the added colloidal fraction. It was shown that the structural changes resulting from increasing amounts of incorporated silica particles pass through distinctively different routes in the case of HPC- and HEC-based films. However, the structures in the two cases are similar at sufficiently high colloidal fraction.

The Novel Organic-Inorganic Hybrid Materials Composed of Phenolic Resin and Silica

Abstract Organic-inorganic hybrid materials composed of phenolic resin and silica were prepared by in-situ polymerization of silicon alkoxides in phenolic resin matrix. The hybrid materials showed uniform morphology with very fine dispersion of silica. The transparency of the hybrid, the size of incorporated silica particles and its interface with matrix resin could be controlled. The uniform hybrid materials showed excellent improvements in mechanical properties.