Nonionic Block Copolymer Surfactants Research Articles

Meso- and Macroporous Polymer Gels for Efficient Adsorption of Block Copolymer Surfactants.

An understanding of surfactant adsorption at solid-liquid interfaces is important for solving many technological problems. This work evaluates surfactant adsorption abilities of high surface area (200-600 m2/g), high porosity (>90%), hierarchically structured open pore polymer gels. Specifically, the interactions of a nonionic block copolymer surfactant, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO), with three polymer gels, namely, syndiotactic polystyrene (sPS), polyimide (PI), and polyurea (PUA) offering different surface energy values, are evaluated at surfactant concentrations below and well above the critical micelle concentration (CMC). Two distinct surfactant adsorption behaviors are identified from the surface tension and nuclear magnetic resonance data. At concentrations below CMC, the surfactant molecules adsorb as a monolayer on polymer strands, inferred from the Langmuir-type adsorption isotherm, with the adsorbed amount increasing with the specific surface area of the polymer gel. The study reports for the first time that the gels show a strong surfactant adsorption above CMC, with the effective surfactant concentration in the gel reaching several folds of the CMC values. The effective surfactant concentration in the gel is analyzed using surfactant micelle size, polymer surface energy, and pore size of the gel. The findings of this study may have strong implications in liquid-liquid separation problems and in the removal of small dye molecules, heavy metal ions, and living organisms from aqueous streams.

Photothermal Breaking of Emulsions Stabilized with Graphene.

Pristine graphene particles prepared using an aqueous phase exfoliation technique have been used to promote the stabilization of emulsions through adsorption at the oil-water interface. Highly localized phase separation of these ultrastable emulsions could, however, be induced through photothermal heating of the graphene particles at the interface exposed to near-infrared light. The graphene wettability, which is a key determinant in preventing droplet coalescence was altered through the adsorption of nonionic block copolymer surfactants. Varying the aqueous solution conditions influenced the hydration of the hydrophilic component of the surfactant providing a further opportunity to alter the overall particle wettability and, hence, stability of the emulsion. In this way, highly stable-oil-in water emulsions were produced with decane; however, water-in-oil emulsions were formed with toluene as the oil phase.

Phase transition of silica in the TMB–P123–H2O–TEOS quadru-component system: A feasible route to different mesostructured materials

Various siliceous structures were obtained using a nonionic block copolymer (Pluronic P123) surfactant and trimethylbenzene (TMB) as a hydrophobic additive by hydrolysis and condensation of tetraethoxysilane (TEOS) in a sol–gel process. The resultant materials were characterized by small-angle X-ray diffraction (SAXRD), nitrogen adsorption analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results revealed the structure transformation from hexagonal structure (HEX) to multilamellar vesicles (MLVs) and then to mesocellular foams (MCFs) in the TMB–P123–H2O–TEOS quadru-component system. The morphology of the mesoporous silica was mainly controlled by the mass ratio of TMB/P123 resulted from the increasing volume of the hydrophobic chain of micelle of P123 that caused by more amount of TMB dissolved in the PPO segment of polymer. The fact that the occurrence of rod-like particles with curved ends and the coexistence of the MLVs and the HEX structure indicates that the MLVs are developed from the ends of HEX structures, rather than formed by a direct cooperative self-assembly mechanism. Further increasing of packing parameter of surfactant resulted from TMB addition transforms lamellar micelles to reversed micelles, leading to the formation of MCFs.

Magnetic solid-phase extraction based on mesoporous silica-coated magnetic nanoparticles for analysis of oral antidiabetic drugs in human plasma

In the present work, magnetic nanoparticles embedded into mesoporous silica were prepared in two steps: first, magnetite was synthesized by oxidation–precipitation method, and next, the magnetic nanoparticles were coated with mesoporous silica by using nonionic block copolymer surfactants as structure-directing agents. The mesoporous SiO2-coated Fe3O4 samples were functionalized using octadecyltrimethoxysilane as silanizing agent. The pure and functionalized silica nanoparticles were physicochemically and morphologically characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The resultant magnetic silica nanoparticles were applied as sorbents for magnetic solid-phase extraction (MSPE) of oral antidiabetic drugs in human plasma. Our results revealed that the magnetite nanoparticles were completely coated by well-ordered mesoporous silica with free pores and stable pore walls, and that the structural and magnetic properties of the Fe3O4 nanoparticles were preserved in the applied synthesis route. Indeed, the sorbent material was capable of extracting the antidiabetic drugs from human plasma, being useful for the sample preparation in biological matrices.

Water-deficient templating system: a general, versatile and efficient synthetic approach for mesoporous silicas

Bridging two current templating systems: diluted surfactant solution and liquid crystal templating approaches, water-deficient templating system allows facile control over mesostructures and morphologies of mesoporous silicas in an efficient way.

Development of Mesoscopic Simulation Studies on Nonionic Block Copolymer Surfactants

Abstract Nonionic block copolymer surfactants, possessing a low stimulation and a low toxicity, have been widely used as pharmaceutical excipients. Studies are conducted on surfactants mainly through experiments. However, through this method, it is difficult to study the solubilization mechanism of surfactants. Mesoscopic simulation, with a shorter period and a lower cost, was beneficial for the study of mechanisms; provided guidelines for experiments and applications; and was, thus, favored by researchers. In recent years, numerous studies have been carried out on nonionic block copolymer surfactants. This article reviewed the effect of mesoscopic simulations on nonionic block copolymer surfactants, aiming at providing an effective method for the study on the mechanism and application of nonionic block copolymer surfactants.

Nafion membranes with ordered mesoporous structure and high water retention properties for fuel cell applications

Ordered mesoporous structures were successfully introduced into Nafion membranesvia a soft micelle templating method, using a non-ionic block copolymer surfactant, PEO127–PPO48–PEO127 (Pluronic F108). Atomic force microscopy (AFM) and small angle X-ray scattering (SAXS) analysis show the typical features of the formation of ordered mesopores in the as-prepared Nafion membranes. TGA and FTIR results show that the mesoporous Nafion (meso-Nafion) has a much higher water retention capability as compared to conventional Nafion membranes. The proton conductivities of meso-Nafion are much higher than those of Nafion 115 membranes especially at reduced relative humidity (RH) and elevated temperatures. The results show that the conductivity and water retention ability are sensitive to the surfactant loading. At 80 °C and 40%RH, the conductivity of the best meso-Nafion membrane is 0.07 S cm−1, 5 times better than 0.013 S cm−1 obtained on Nafion 115. At 60%RH and 80 °C, the cell with meso-Nafion reached a stable power output of 0.63 W cm−2, more than 2 times higher than the cell with pristine Nafion 115 under identical experimental conditions. When the RH reduced to 20%, the power output of meso-Nafion membranes is 5.6 times higher than that of Nafion 115. The cells with meso-Nafion membranes also demonstrate much better power output at elevated temperature of 120 °C and reduced humidity.

Tuning the morphology and the structure of hierarchical meso–macroporous silica by dual templating with micelles and solid lipid nanoparticles (SLN)

Solid lipid nanoparticles (SLN) stabilized by nonionic polysorbate or block copolymer surfactants were used for the preparation of hierarchical meso–macroporous silica through a co-templated approach combining a cooperative templating mechanism (CTM) with micelles and spherical soft matter particles imprinting. Depending on the reaction conditions, the morphology of the final material can be tuned to capsules or to block matter. The size of the mesopores is strongly dependent on the nature of the surfactant in excess: 3 nm (Tween 20), 5 nm (Tween 40) or 9 nm (Pluronic® P123), whereas the size of the macropores depends only on the size of SLN (250 ± 150 nm). The macroporous texture was clearly evidenced by TEM. The organization degree of the silica wall depends on the surfactant: only wormlike mesoporous capsules were obtained with Tween 20, and hexagonally ordered microdomains embedded in wormlike mesoporous silica capsules were obtained with Tween 40. Hexagonally ordered silica with circularly ordered mesoporosity could be achieved with Pluronic block copolymer P123. Combining mesoporous silica with solid lipid nanoparticles is a straightforward approach for the design of advanced formulations in drug delivery or food chemistry.

Mesoporous Nafion Membranes for Fuel Cell Applications

Ordered mesoporous structures were successfully introduced into Nafion membranes via a soft micelle templating method, using a nonionic block copolymer surfactant, PEO127-PPO48-PEO127 (Pluronic F108). The mesoporous Nafion or meso-Nafion membranes were characterized by the AFM, SAXS, TGA and conductivity measurements. The results show that the meso-Nafion has a very high water retention capability. The proton conductivities of meso-Nafion are also much higher than that of Nafion 115 membranes particularly at reduced relative humidity (RH) and elevated temperatures. At 80oC and 40%RH, the conductivity of meso-Nafion is 0.07 Scm-1, more than 3 times better than Nafion 115. At 60%RH and 80oC, the cell with meso-Nafion reached a stable power output of 0.63 Wcm-2, more than 2 times higher than the cell with pristine Nafion 115 under identical experimental conditions. The cells with meso-Nafion membrane also demonstrate much better stability at elevated temperature of 120oC and reduced humidities.

Synthesis and in-vitro bioactivity of mesoporous bioactive glasses with tunable macropores

By using a nonionic block copolymer surfactant as the mesostructure directing agent, polystyrene (PS) colloidal particles or polyester (Terylene®) fibers as the macropore templates, mesoporous bioactive glass (MBG) materials with tunable macropores in a wide range (0.6–200 μm) have been synthesized and their in vitro bioactivities have been studied. Macro-mesoporous bioactive glass (MMBG) materials obtained by using PS spherical templates have a uniform macropore size of ∼600 nm, while MBG materials synthesized in the presence of terylene fibers have tubular channels (denoted TMBG) with diameters in the range of 8–200 μm adjusted by the diameters of terylene fibers. Both MMBG and TMBG materials have uniform mesopores of ∼5 nm in diameter. Similar to MBG materials, MMBG and TMBG materials have superior in vitro bioactivity compared to conventional bioactive glass. It is also shown that the size of macropore exerts influence on the hydroxycarbonate apatite (HCA) growth behavior within macropores. After soaking MMBG in simulated body fluid, HCA spheres gradually grow to sizes comparable to that of macro-pores after 24 h. While in the case of TMBG, hollow HCA tubes form in the tubular channels of TMBG. It is expected MBG materials with tunable macropores and exceptional in vitro bioactivity may find potential applications in delivery of biological factors, tissue ingrowth, tissue regeneration and neovascularization.

Evaluation of Nonionic Block Polymer Surfactants in Maize Root Proteome Extraction within Water–Organic Solvent Phases

In the present work, six nonionic block copolymer surfactants consisting of poly(ethylene glycol) (PEG), polyethylene (PE), and poly(propylene glycol) (PPG) were exploited to extract total proteins from maize (Zea mays L.) roots within a water–organic solvent system. After the treatment, proteins were partitioned into aqueous phase, interphase, and organic phase. The total yield was increased by up to 30% after adding PE-PEG block polymer surfactant compared with control. Two-dimensional electrophoresis (2-DE) was further used to evaluate proteins in water phase and interphase; the results revealed that the spot numbers and density were all improved, and well-focused electrophoretic patterns were achieved with higher density and without excess Joule heating problem after adding nonionic block polymer surfactants. Among the six investigated block polymers, PE-PEG extracted the largest amount of proteins.

The in vitro bioactive of sol–gel bioactive glass powders with three-dimensional lamellar structure

In this study, three-dimensional lamellar structured bioactive glass powders were prepared using nonionic block copolymer surfactants as structure-directing agents through a sol–gel method. The characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectrograph (FTIR), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) were used for determination of the particles structure before and after immersion in simulated body fluid (SBF) for various numbers of days. The results show that the biomineralized products on the surfaces of the bioactive glass powders were apatite microcrystals with a low crystallinity, the composition and morphologies of the apatite microcrystals changed with the immersion time increased. The presence of the apatite layer indicates biomineralization.

One pot synthesis of mesostructured non-silica oxides nanocrystallites

Some typical worm-like mesoporous non-silica oxides, titania, zirconia, and dopants-incorporated zirconia oxides, with homogeneous nanocrystalline framework and narrow pore-size distribution have been synthesized via a facile process templated from composite surfactant of a long chain poly block copolymer combined with non-ionic alkyl-PEO surfactant (Brij56) under the hydrothermal condition. Bi- or even multi-component zirconia-based composites with further addition of other oxide compositions can also be obtained with well-defined mesoporous structure and nanocrystalline framework. These mesostructured oxides/composite oxides show high surface area, well-crystallization framework, and high thermal stability. XRD, nitrogen adsorption analysis, TEM, and EDX were used for the structural characterizations. The use of non-ionic block-copolymer surfactant is believed to be responsible for the crystallization of mesoporous framework and high thermal stability at high temperature without structural collapse.

Study of mesoporous silica/magnetite systems in drug controlled release

Ordered mesoporous materials like SBA-15 have a network of channels and pores with well-defined size in the nanoscale range. This particular silica matrix pore architecture makes them suitable for hosting a broad variety of compounds in very promising materials in a range of applications, including drug release magnetic carriers. In this work, magnetic nanoparticles embedded into mesoporous silica were prepared in two steps: first, magnetite was synthesized by oxidation-precipitation method, and next, the magnetic nanoparticles were coated with mesoporous silica by using nonionic block copolymer surfactants as structure-directing agents. The materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N(2) adsorption, and scanning electron microscopy (SEM). The influence of magnetic nanoparticles on drug release kinetics was studied with cisplatin, carboplatin, and atenolol under in vitro conditions in the absence and in the presence of an external magnetic field (0.25 T) by using NdFeB permanent magnet. The constant external magnetic field did not affect drug release significantly. The low-frequency alternating magnetic field had a large influence on the cisplatin release profile.

Adsorption of ethoxylated styrene oxide and polyacrylic acid and mixtures there of on organic pigment

The adsorption of two polymeric surfactants on an organic pigment was investigated. As surfactants the anionic polyacrylic acid sodium salt (PANa, M W = 15 , 000 ) and a non-ionic block copolymer surfactant based on styrene oxide (SO) and ethylene oxide (EO) ( M W = 1500 ) were used. The adsorption behavior was analyzed by size exclusion chromatography of the supernatant after centrifugation of the pigment dispersions. It was found that PANa has no affinity to the pigment, whereas SO–EO has a strong affinity to the pigment surface. Competitive adsorption of PANa and SO–EO was not observed. Addition of SO–EO yields stable dispersions.

Mesoporous silica–magnetite nanocomposite synthesized by using a neutral surfactant

Magnetite nanoparticles coated by mesoporous silica were synthesized by an alternative chemical routeusing a neutral surfactant and without the application of any functionalization method. The magnetite(Fe3O4)nanoparticles were prepared by precipitation from aqueous media, and then coated with mesoporoussilica by using nonionic block copolymer surfactants as the structure-directing agents. The mesoporousSiO2-coatedFe3O4 samples were characterized by x-ray diffraction, Fourier-transform infrared spectroscopy,N2 adsorption–desorption isotherms, transmission electron microscopy,57Fe Mössbauer spectroscopy, and vibrating sample magnetometry. Our results revealed that the magnetitenanoparticles are completely coated by well-ordered mesoporous silica with free pores and stable(∼8 nm thick) pore walls, and that the structural and magnetic properties of theFe3O4 nanoparticles are preserved in the applied synthesis route.

Performance impact of dynamic surface coatings on polymeric insulator-based dielectrophoretic particle separators

Efficient and robust particle separation and enrichment techniques are critical for a diverse range of lab-on-a-chip analytical devices including pathogen detection, sample preparation, high-throughput particle sorting, and biomedical diagnostics. Previously, using insulator-based dielectrophoresis (iDEP) in microfluidic glass devices, we demonstrated simultaneous particle separation and concentration of various biological organisms, polymer microbeads, and viruses. As an alternative to glass, we evaluate the performance of similar iDEP structures produced in polymer-based microfluidic devices. There are numerous processing and operational advantages that motivate our transition to polymers such as the availability of numerous innate chemical compositions for tailoring performance, mechanical robustness, economy of scale, and ease of thermoforming and mass manufacturing. The polymer chips we have evaluated are fabricated through an injection molding process of the commercially available cyclic olefin copolymer Zeonor 1060R. This publication is the first to demonstrate insulator-based dielectrophoretic biological particle differentiation in a polymeric device injection molded from a silicon master. The results demonstrate that the polymer devices achieve the same performance metrics as glass devices. We also demonstrate an effective means of enhancing performance of these microsystems in terms of system power demand through the use of a dynamic surface coating. We demonstrate that the commercially available nonionic block copolymer surfactant, Pluronic F127, has a strong interaction with the cyclic olefin copolymer at very low concentrations, positively impacting performance by decreasing the electric field necessary to achieve particle trapping by an order of magnitude. The presence of this dynamic surface coating, therefore, lowers the power required to operate such devices and minimizes Joule heating. The results of this study demonstrate that iDEP polymeric microfluidic devices with surfactant coatings provide an affordable engineering strategy for selective particle enrichment and sorting.

The in-vitro bioactivity of mesoporous bioactive glasses

Ordered mesoporous bioactive glasses (MBGs) with different compositions were prepared by using nonionic block copolymer surfactants as structure-directing agents through an evaporation-induced self-assembly process. Their in-vitro bioactivities were studied in detail by electron microscopy, Fourier-transform infrared spectroscopy, and inductively coupled plasma (ICP) atomic emission spectroscopy. The ICP element analysis results were further calculated in terms of the total consumption of Ca and P, Δ[Ca]/Δ[P] ratios, and ionic activity product (IP) of hydroxyapatite. Through the above analysis, it is clear that MBGs show a different structure–bioactivity correlation compared to conventional sol–gel-derived BGs. The in vitro bioactivity of MBGs is dependent on the Si/Ca ratio in the network when the other material parameters such as the mesostructure and texture properties (pore size, pore volume) are controlled. MBG 80S15C with relatively lower calcium content exhibits the best in vitro bioactivity, in contrast to conventional sol–gel-derived BGs where usually higher calcium percentage BGs (e.g. 60S35C) show better bioactivity. Calcination temperature is another important factor that influences the in vitro bioactivity. According to our results, MBGs calcined at 973 K may possess the best in vitro bioactivity. The influences of the composition and calcination temperature upon bioactivity are explained in terms of the unique structures of MBGs.

Nonionic Block Copolymer and Anionic Mixed Surfactants Directed Synthesis of Highly Ordered Mesoporous Silica with Bicontinuous Cubic Structure

Mesoporous silica with Ia3̄d structure has been successfully prepared by using mixed surfactants of commercially available nonionic block copolymer P123 (EO20PO70EO20) and anionic sodium dodecyl sulfate (SDS) as structure-directing agents through an acid-catalyzed silica sol−gel process. XRD, TEM, and N2 sorption measurements show that the products have highly ordered bicontinuous cubic mesostructure with high surface area (∼770 m2/g), large pore volume (∼1.5 cm3/g), and uniform pore size (∼10 nm). Effects of preparation parameters on the formation of the mesostructure have been extensively investigated. It is found that the molar ratios of SDS/P123 between 2.1 and 2.5 and that of silicic species to P123 in the range from 40 to 75 are favorable for the formation of highly ordered Ia3̄d mesostructure. Prolonging hydrothermal treatment time leads to almost unchanged cell parameters of the products, whereas there is obvious increase of the pore sizes and pore volume. The results show that resultant template-free mesoporous silica products have excellent thermal stability, and they are more stable in N2 atmosphere than in air. Morphologies of the resultant materials can be further controlled by adding inorganic salt (such as Na2SO4) into the mixed surfactants system. Coral- and petaline-like mesoporous silica with continuous skeletons can be obtained. Understanding this synthesis system might be useful for economical and large-scale production of mesoporous materials with controllable structures.

Simultaneous drying and chemical modification of hierarchically organized silica monoliths with organofunctional silanes

Large, low density silica monoliths with a hierarchical organisation of macro- and periodically arranged mesopores are prepared by a true liquid crystal templating approach of an ethylene glycol-modified silane in the presence of a non-ionic block copolymer surfactant and subsequent drying of the wet gels with organosilanes. In this approach the silanes serve two functions: first, the silylation reactions allow for non-destructive drying of the monolithic gels and simultaneous extraction of the block copolymer template; second, they serve as surface functionalization agent. A variety of organofunctional silanes such as trimethylchlorosilane, 3-mercaptopropyltrimethoxysilane, phenyl-trimethoxysilane, 3-[(2,2-dimethyl-1-aza-2-silacyclopent-1-yl)dimethylsilyl]-1-propanamine, a cyclic silazane resulting in aminopropyldimethylsilyl groups on the silica surface, and (methylmethacryloyl)dimethyl-methoxysilane, has been successfully applied in the interfacial modification of the silica surface. The resulting silica monoliths were characterized with respect to their structure by SEM, SAXS, and nitrogen sorption and with respect to their chemical composition by elemental analysis, titrations and MAS-NMR spectroscopy.