Triblock Copolymer Surfactant Research Articles

Generation of toxic degradation products by sonication of Pluronic® dispersants: implications for nanotoxicity testing

Poloxamers (known by the trade name Pluronic®) are triblock copolymer surfactants that contain two polyethylene glycol blocks and one polypropylene glycol block of various sizes. Poloxamers are widely used as nanoparticle dispersants for nanotoxicity studies wherein nanoparticles are sonicated with a dispersant to prepare suspensions. It is known that poloxamers can be degraded during sonication and that reactive oxygen species contribute to the degradation process. However, the possibility that poloxamer degradation products are toxic to mammalian cells has not been well studied. We report here that aqueous solutions of poloxamer 188 (Pluronic® F-68) and poloxamer 407 (Pluronic® F-127) sonicated in the presence or absence of multi-walled carbon nanotubes (MWNTs) can became highly toxic to cultured cells. Moreover, toxicity correlated with the sonolytic degradation of the polymers. These findings suggest that caution should be used in interpreting the results of nanotoxicity studies where the potential sonolytic degradation of dispersants was not controlled.

Epoxidation of Styrene using Nanosized γ-Al2O3/NiO Heterogeneous Catalyst Derived from the P123 Surfactant

Al₂O₃/NiO powder was obtained through hydrolysis-condensation reactions and thermal treatments. An organic additive, triblock copolymer surfactant P123, was added to the starting materials to control the surface area and morphology. The synthesized powder was characterized by X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM) and a Brunner-Emmett-Teller surface analysis (BET). The heterogeneous catalytic activity of this powder was applied to an epoxidation reaction of styrene and was monitored using a gas chromatograph with mass spectrophotometry (GC/MS).

Pore Morphology Control of Mesostructured SO42−/ZrO2‐Based Hybrid Catalysts Functionalized by Alkyl‐Bridged Organosilica Moieties for Biodiesel Production From Non‐Edible Oil

AbstractA series of mesostructured SO42−/ZrO2‐based hybrid materials functionalized with alkyl‐bridged organosilica species, forming SO42−/ZrO2‐SiO2(Ph/Et), were developed by using a single step co‐condensation technique with hydrothermal treatment in the presence of triblock copolymer surfactants. By tuning the molar ratios of the starting precursors, the types of surfactant and the preparation conditions, as‐prepared SO42−/ZrO2‐SiO2(Ph/Et) exhibited 2 D hexagonal p6mm, 3 D cubic Im3m and 3 D interconnected, worm‐hole‐like pore geometries. The mesostructure, morphology, porosity, and composition, as well as acid property of as‐prepared materials were characterized. As a novel, reusable, solid acid catalyst, the hybrid materials were applied for the biodiesel production from a non‐edible oil (Eruca sativa Gars. oil) under mild conditions; considerably high catalytic activity and stability were observed. Special attention was paid to the influences of the textural properties on the activity of SO42−/ZrO2‐SiO2(Ph/Et) materials to the target reaction.

Face-Centered-Cubic Large-Pore Periodic Mesoporous Organosilicas with Unsaturated and Aromatic Bridging Groups

Large-pore ethenylene-bridged (-CH═CH-) and phenylene-bridged (-C(6)H(4)-) periodic mesoporous organosilicas (PMOs) with face-centered-cubic structure (Fm3m symmetry) of spherical mesopores were synthesized at 7 °C at low acid concentration (0.1 M HCl) using Pluronic F127 triblock copolymer surfactant in the presence of aromatic swelling agents (1,3,5-trimethylbenzene, xylenes-isomer mixture, and toluene). In particular, this work reports an unprecedented block-copolymer-templated well-ordered ethenylene-bridged PMO with cubic structure of spherical mesopores and an unprecedented block-copolymer-templated face-centered cubic phenylene-bridged PMO, which also has an exceptionally large unit-cell size and pore diameter. The unit-cell parameters of 30 and 25 nm and the mesopore diameters of 14 and 11 nm (nominal BJH-KJS pore diameters of 12-13 and 9 nm) were obtained for ethenylene-bridged and phenylene-bridged PMOs, respectively. Under the considered reaction conditions, the unit-cell parameters and pore diameters were found to be similar when the three different methyl-substituted benzene swelling agents were employed, although the degree of structural ordering appeared to improve for phenylene-bridged PMOs in the sequence of decreased number of methyl groups on the benzene ring.

Simulation-Aided Design and Synthesis of Hierarchically Porous Membranes

Free-standing silica membranes with hierarchical porosity (ca. 300 nm macropores surrounded by 6-8 nm mesopores) and controllable mesopore architecture were prepared by a dual-templating method, with the structural design aided by mesoscale simulation. To create a two-dimensional, hexagonal macropore array, polymeric colloidal hemisphere arrays were synthesized by a two-step annealing process starting with non-close-packed polystyrene sphere arrays on silicon coated with a sacrificial alumina layer. A silica precursor containing a poly(ethylene) oxide-poly(propylene oxide)-poly(ethylene) oxide (PEO-PPO-PEO) triblock-copolymer surfactant as template for mesopore creation was spin-coated onto the support and aged and then converted into the free-standing membranes by dissolving both templates and the alumina layer. To test the hypothesis that the mesopore architecture may be influenced by confinement of the surfactant-containing precursor solution in the colloidal array and by its interactions with the polymeric colloids, the system was studied theoretically by dissipative particle dynamics (DPD) simulations and experimentally by examining the pore structures of silica membranes via electron microscopy. The DPD simulations demonstrated that, while only tilted columnar structure can be formed through tuning the interaction with the substrate, perfect alignment of 2D hexagonal micelles perpendicular to the plane of the membrane is achievable by confinement between parallel walls that interact preferentially with the hydrophilic components (PEO blocks, silicate, and solvent). The simulations predicted that this alignment could be maintained across a span of up to 10 columns of micelles, the same length scale defined by the colloidal array. In the actual membranes, we manipulated the mesopore alignment by tuning the solvent polarity relative to the polar surface characteristics of the colloidal hemispheres. With methanol as a solvent, columnar mesopores parallel to the substrate were observed; with a methanol-water mixed solvent, individual spherical mesopores were present; and with water as the only solvent, twisted columnar structures were seen.

The Use of Tri-Block Copolymer Surfactants as Promoters to Improve Flotation Recovery of Poorly Floating Coal Components

The use of tri-block copolymer surfactants as flotation promoters to enhance the recovery of poorly floating components of coal is examined. Previous study of the flotation response of different coal components using the coal grain analysis tool showed that coarse particles of inertinite, inertinite-rich, and vitrinite-rich composites were poorly recovered compared with liberated vitrinite. Improved recovery of these poorly floating components by using targeted reagents could boost the saleable product coal and, hence, economic outcomes. This approach requires only minor modifications to existing fines circuits. The reagents used were surfactants from the group of tri-block copolymers of polyethylene oxide/polypropylene oxide. The tests were complemented by the coal grain analysis tool that allowed the impact of the reagents on the recovery of the problem components to be properly assessed. Laboratory and full-scale flotation experiments were conducted by adding small amounts of the promoters before adding conventional collector (diesel). Flotation recovery was significantly increased with only a small product ash penalty in each case. Coal grain analysis showed that recovery was improved for most components, especially the coarse composite grains.

Facile synthetic route to implement a fully bendable organic metal–insulator–semiconductor device on polyimide sheet

Triblock copolymer surfactant, HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H (i.e. P123)-based nanocrystalline (nc)-TiO2 thin film had been synthesized on organic flexible polyimide (PI) sheet for their application in organic metal–insulator–semiconductor (MIS) device. The nc-TiO2 film over PI was successfully deposited for the first time by a systematic solution proceeds dip-coating method and by the assistance of triblock copolymer surfactant. The effect of annealing temperature (270°C, 5h) on the texture, morphology and time-induced hydrophilicity was studied by X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle system, respectively, to examine the chemical composition of the film and the contact angle. The surface morphology of the semiconducting layer of organic pentacene was also investigated by using AFM and XRD, and confirmed that continuous crystalline film growth had occurred on the nc-TiO2 surface over flexible PI sheet. The semiconductor–dielectric interface of pentacene and nc-TiO2 films was characterized by current–voltage and capacitance–voltage measurements. This interface measurement in cross-link MIS structured device yielded a low leakage current density of 8.7×10−12Acm−2 at 0 to −5V, maximum capacitance of 102.3 pF at 1MHz and estimated dielectric constant value of 28.8. Furthermore, assessment of quality study of nc-TiO2 film in real-life flexibility tests for different types of bending settings with high durability (c.a. 30days) demonstrated a better comprehension of dielectric properties over flexible PI sheet. We expected them to have a keen interest in the scientific study, which could be an alternate opportunity to the excellent dielectric–semiconductor interface at economic and low temperature processing for large-area flexible field-effect transistors and sensors.

Ordered mesoporous antireflective films for 1053 nm high power pulse laser

Single-layer silica films are prepared via evaporation-induced-self-assembling process using triblock copolymer surfactant F127 as template and tetraethoxysiliane as precursor under acidic condition. After ammonia pretreatment, the as-deposited films undergo a thermal decomposition process to remove the surfactant, and the mesopores are formed in film. Three techniques are used to characterize the mesoscopic structure of film, i.e., grazing-incidence X-ray diffraction, nitrogen adsorption/desorption and transmission electron microscopy. The results indicate that the film has an ordered cage-like porous structure and can be indexed as the body-centered-cubic arrangement. The optical properties of the films are investigated via ellipsometry and UV-VIS-NIR transmission spectrometer. The transmitance can reach up to 99.9% at 1053 nm wavelength. The refractive index varies with the molar ratio of F127/Si. Atomic force microscope is used to probe the surface morphology, and the surface roughness Ra is 1.2 nm. A 1053 nm laser is used to determine the laser damage threshold of film and all the thresholds are higher than 25 J· cm-2 (1 ns). This method has a potential application in the preparation of large-aperture antireflective films.

Preparation of ethane-bridged organosilica group and keggin type heteropoly acid co-functionalized ZrO2 hybrid catalyst for biodiesel synthesis from eruca sativa gars oil

A series of mesostructured ZrO2-based hybrid catalysts, functionalized by both an ethane-bridged organosilica group and the Keggin type heteropoly acid, H3PW12O40–ZrO2–Si(Et)Si, were prepared by one-step sol-gel-hydrothermal method in the presence of a triblock copolymer surfactant (F127). The materials were well characterized by spectroscopy methods such as FT-IR and MAS NMR, transmission electron microscopy, and nitrogen gas physisorption measurements to confirm the structural integrity of the Keggin units and ethane-bridged organosilica groups in the hybrid materials, and to test the mesostructure, morphology, and porosity of the materials. The materials were subsequently utilized as environmentally-friendly solid acid catalysts in the transesterification of low-cost Eruca Sativa Gars oil with methanol to produce fatty acid methyl esters under atmosphere refluxing. Compared with alkyl-free H3PW12O40–ZrO2, the prepared H3PW12O40–ZrO2–Si(Et)Si exhibited higher catalytic activity toward the target reaction. This enhanced acid-catalytic activity after the introduction of both acidic and hydrophobic functionalities within the ZrO2 matrix was explained in terms of strong Brϕnsted acidity, excellent porosity, and enhanced hydrophobicity of the hybrid materials.

Synthesis and formation mechanism of TS-1@mesosilica core–shell materials templated by triblock copolymer surfactant

Micro-/mesoporous composite materials that possessed core–shell structure were prepared through oriented assembly of mesoporous silica on premade titanosilicate zeolite TS-1 using triblock copolymer surfactant P123 as template in an acid-free system. When the pH value of P123/NaCl/H2O/EtOH/TEOS/TS-1 synthetic system was controlled in the range of 3.5–5.5, the crystalline particles of TS-1 were negatively charged, whereas P123 micelles were partially protonated. Thus induced an electrostatic interaction between inorganic zeolite and organic micelles probably via enhanced hydrogen bonding, and made an oriented assembly of silica oligomer or silica-micelle composite on the surface of P123/TS-1 and further condensation. Otherwise, the silica was self-assembled in a phase separation manner, or failed to form a mesophase. The mesopores in silica shell were of wormhole-like and interconnected with the micropores in TS-1. When as-synthesized core/shell composites were hydrothermally post-treated, the pore volume, specific surface area and pore size of shell increased with increasing temperature. The average shell thickness and particle size were conveniently adjusted in the range of 30–90nm and 350–500nm, respectively, by changing the synthesis time, temperature, and amount of silica source added.

MG ATP AND ANTIOXIDANTS AUGMENT THE RADIOPROTECTIVE EFFECT OF SURFACTANT COPOLYMERS

Mediated by reactive oxygen species, the damaging effects of high-intensity ionizing irradiation on tissues are dose, frequency, oxygen concentration, and tissue property dependent. Intense ionizing irradiation exposure may cause rapid cellular necrosis by peroxidation of membrane lipids leading to membrane disruption. This leads to a loss of the transmembrane ionic gradients and a subsequent depletion of the cellular ATP store, followed by cellular generation of reactive oxygen species. When membrane disruption is extensive, acute cellular necrosis follows. Triblock copolymer surfactants, such as Poloxamer 188 (P188), are able to seal damaged rhabdomyocyte membranes, increasing post-irradiation viability. Separated rat rhabdomyocytes were exposed to 40 Gy (Co 1.5 Gy min) irradiation and treated at 20 min intervals with combination permutations of P188, N-acetylcysteine (NAC), and Mg-ATP. Cell viability at 18 and 48 h was determined using Calcein-AM and Ethidium Homodimer-1 staining. At 18 h after irradiation, the combined administration of P188, ATP, and NAC restored cell viability rates to near sham-exposed levels of 60%. At 48 h post-irradiation, cell viability dropped substantially to the 7-20% range, regardless of attempted intervention. Nevertheless, the combination of P188, ATP, and NAC more than doubled cell viability at the 48-h time point. Neither 8 kDa polyethylene glycol nor 10 kDa neutral dextran was as effective in enhancing cell viability. These results indicate that antioxidants and cellular energy substrates improve the efficacy of membrane-sealing copolymer surfactants in prolonging cellular viability following massive radiation exposure.

Can Carbon Spheres Be Created through the Stöber Method?

Monodisperse colloidal nanospheres, including those composed of silica, polymers, and carbon, have received considerable attention during the past decade because they promise wide applications in drug delivery, active material encapsulation, colloidal catalysts, and particle templates. The success of all these applications strongly depends on the availability of colloidal spheres with tightly controlled sizes and surface properties, and on their ability to self-assemble into ordered superstructures. The classical Stcber method, which usually relies on sol–gel chemistry involving the hydrolysis of tetraalkyl silicates in an alcohol/water solution using ammonia as the catalyst, is a general approach for the synthesis of silica spheres having a size mostly in the range of 150–500 nm. Monodisperse polymer spheres, such as polystyrene, poly(methyl methacrylate), and poly(hydroxyethyl methacrylate) can be prepared by the emulsion polymerization approach. However, these colloidal spheres have failed to be converted into their carbonaceous analogues because of thermal decomposition. Differing from most polymers and silica materials, carbon materials in general show a series of excellent characteristics such as high surface area, high thermal stability (in an inert atmosphere), and acid/ base resistance, and can be applied in harsh reaction conditions. Hence, to integrate the advantages of carbon materials and colloids into one type of material, remains a grand challenge, which could be exploited by the new synthesis of monodisperse colloidal carbon spheres. Phenolic resins derived from the polymerization of phenols (e.g. phenol, resorcinol) and aldehydes (e.g. formaldehyde, furfuraldehyde), are commonly employed as excellent precursors for the production of carbon materials. Although there are several reports regarding the synthesis of carbon microspheres and nanospheres from phenolic resins, it is rather rare to find a report about truly monodisperse phenolic resin nanospheres that can form colloidal crystals by self-assembly. Recently, Liu et al. smartly associated the synthesis of carbon spheres with silica spheres. They considered that the synthesis of silica spheres based on the Stcber method involves the condensation of silicon alkoxides (e.g. tetraethyl orthosilicate (TEOS)) in ethanol/water mixtures under alkaline conditions (e.g. ammonia solution) at room temperature. Coincidentally, the resorcinol-formaldehyde precursors exhibit structural similarities to silanes, i.e. similar coordination sites and tetrahedral geometry, so their condensation behavior should be analogous to the hydrolysis and subsequent condensation of silicon alkoxides. Hence, a curious question arises: can carbon spheres really be created by the Stcber method? The answer is “yes”. Liu et al. have developed methods that are inspired by and exploit the Stcber method for the synthesis of monodisperse resorcinol-formaldehyde (RF) resin polymer colloidal spheres and their carbonaceous analogues (Figure 1). The particle size of the obtained colloidal products can be easily tuned by changing the ratio of alcohol to water, changing the amounts of NH4OH and of the RF precursor, using alcohols with short alkyl chains, and introducing a triblock copolymer surfactant. Critical to the successful synthesis of such polymer spheres is the use of ammonia in the reaction system; its role, they consider, lies in not only accelerating the polymerization of RF, but also supplying the positive charges that adhere to the outer surface of the spheres and thus, prevent the aggregation. Firstly, ammonia molecules catalyze the polymerization of RF inside the emulsion droplets, thus initiating their condensation process. Resorcinol reacts quickly with formaldehyde, forming numerous hydroxymethyl-substituted species. These hydroxymethyl-substituted species are positioned at the surface of the emulsion droplets owing to the electrostatic interaction with the ammonia molecules, and further cross-linking of these species during the hydrothermal treatment results in uniform colloidal spheres. The ammonia, indeed, plays a key role in such a copolymerization system. However, it may serve other functions than that mentioned above, and this ability may lead to a rather different reaction sequence. Early in 1948, Richmond et al. investigated the reaction between formaldehyde and ammonia, and found that a fast reaction occurs after their mixing, thus resulting in cyclotrimethylenetriamine as the intermediate in the eventual formation of hexamine. This was further confirmed by a recent report which shows [*] Prof. A.-H. Lu, G.-P. Hao, Q. Sun State Key Laboratory of Fine Chemicals School of Chemical Engineering, Dalian University of Technology Dalian 116024 (P.R. China) E-mail: anhuilu@dlut.edu.cn

Improving the visible light photocatalytic activity of mesoporous TiO 2 via the synergetic effects of B doping and Ag loading

B-doped together with Ag-loaded mesoporous TiO 2 (Ag/B–TiO 2) was prepared by a two-step hydrothermal method in the presence of boric acid, triblock copolymer surfactant, and silver nitrate, followed by heat treatment. The obtained samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption. It was revealed that all samples consist of highly crystalline anatase with mesoporous structure. For Ag/B–TiO 2, B was doped into TiO 2 matrix in the form of both interstitial B and substitutional B while Ag was deposited on the surface of B–TiO 2 in the form of metallic silver. Compared with the single B-doped or Ag-loaded TiO 2 one, mesoporous Ag/B–TiO 2 exhibits much higher visible light photocatalytic activity for the degradation of Rhodamine 6G, which can be ascribed to the synergistic effects of B doping and Ag loading by narrowing the band gap of the photocatalyst and preventing the fast recombination of the photogenerated charge carriers, respectively.

One‐Step Preparation of Efficient and Reusable SO42−/ZrO2‐Based Hybrid Solid Catalysts Functionalized by Alkyl‐Bridged Organosilica Moieties for Biodiesel Production

A series of mesoporous sulfated zirconia materials functionalized by alkyl-bridged organosilica moieties (SO(4)(2-)/ZrO(2)-SiO(2)(R) with various S/Si or Zr/Si molar ratios and R=CH(2)CH(2) or C(6)H(4)) were developed by a one-step co-condensation technique combined with hydrothermal treatment with the aid of a triblock copolymer surfactant (P123). The structures, morphologies, porosities, and acid properties of the materials were well characterized. Subsequently, the catalytic performances (activity and stability) of SO(4)(2-)/ZrO(2)-SiO(2)(R) were evaluated by the transesterification of both pure triglyceride (tripalmitin) and low-cost virgin plant oil (Eruca sativa Gars. oil) with methanol for biodiesel production under mild conditions (atmospheric pressure, 65 °C), and the enhanced catalytic activity with respect to alkyl-free sulfated zirconia was obtained. This excellent catalytic activity was explained in terms of the inherent Brønsted acidity, well-defined mesoporosity, and increased hydrophobicity of the as-prepared, hybrid, solid acid catalyst.

Synthesis of Highly Efficient WO<sub>3</sub>-Doped MCF Catalyst and Its Application in the Selective Oxidation of Cyclopentene to Glutaraldehyde

Synthesis of Highly Efficient WO<sub>3</sub>-Doped MCF Catalyst and Its Application in the Selective Oxidation of Cyclopentene to Glutaraldehyde

Preparation of heterostructured mesoporous In2O3/Ta2O5 nanocomposites with enhanced photocatalytic activity for hydrogen evolution

Abstract A heterostructured mesoporous In 2 O 3 /Ta 2 O 5 nanocomposite photocatalyst for hydrogen production was prepared by a one-step sol-gel process, employing a triblock copolymer surfactant (Pluronic P123) as a structure-directing agent. The incorporation of In 2 O 3 significantly improves the thermal stability of mesoporous Ta 2 O 5 and gets heterostructured In 2 O 3 /Ta 2 O 5 nanocomposites with a reduced band gap. The as-prepared In 2 O 3 /Ta 2 O 5 nanocomposite shows an obviously enhanced photocatalytic activity for hydrogen production with a long-term stability due to the synergistic effect of the heterojunctions and the large specific surface area as well as the thin walls from the mesoporous structures.

Ordering in Mixtures of a Triblock Copolymer with a Room Temperature Ionic Liquid

Well-ordered block copolymer (BCP) morphologies are obtained by blending PEO−PPO−PEO triblock copolymer surfactants with the room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate. The selective association of the IL with the PEO blocks increases the segregation strength by raising the effective interaction parameter between the PEO and PPO blocks. Therefore, the copolymer/IL blends form well-ordered microdomains in the melt, whereas the neat copolymers are phase mixed. The IL is shown to interact with the PEO chains of the copolymers by a depression in the melting point of the PEO crystals with increasing IL concentration. Wide-angle X-ray diffraction and polarized optical microscopy also show a disruption of PEO crystallization in the copolymer/blends. Infrared spectroscopy indicates a favorable enthalpic interaction between the PEO blocks and the IL, which does not exist between PPO and the IL. Small-angle X-ray scattering confirms the enhanced ordering of the copolymers upon addition of the IL, the formation of well-ordered microdomains, and a change in the characteristic spacing with increasing IL concentration.

Aggregation behavior and complex structure between triblock copolymer and anionic surfactants

The aggregation behavior and complex structure of ABA triblock copolymer EO 76PO 30EO 76 (F68) with sodium dodecyl sulfate (SDS) and sodium bis(2-ethylhexyl)sulfonate (AOT) in aqueous solution were investigated by surface tension, fluorescence techniques and dynamic light-scattering (DLS) measurements. It is revealed that in certain regions of binding, surfactant/F68 complexes are formed. Structural informations and size of complexes are evaluated. When F68 is present in its nonassociated state, F68/micellar SDS complexes are formed at SDS concentrations above its critical aggregation concentration (cac). The cac is well below the critical micellar concentration (cmc) of pure SDS, and a model suggesting how complexes are formed at the cac in the presence of F68 is described. Experimental results show that SDS interacts with F68 mainly through hydrophobic forces, polypropylene oxide (PPO) groups of F68 are solubilized into SDS micellar cores and poly(ethylene oxide) (PEO) groups interact with SDS micelles. This interaction mechanism results in a “pearl-necklace” complex structure. However, a different structure occurs for F68/AOT complex at lower F68 concentrations, as nonassociated F68 interacts with AOT mainly through ion–dipole interactions. Complexes with a “wrapping” structure at lower F68 concentrations are formed.

Hydrogen-Bond-Mediated Phase Behavior of Complexes of Small Molecule Additives with Poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) Triblock Copolymer Surfactants

The addition of multifunctional additives comprised of single- or double-ring aromatic cores decorated at their periphery with multiple hydrogen-bond-donating groups such as carboxylic acid and phenol is shown to induce microphase segregation of otherwise disordered Pluronic BCP (poly(ethylene oxide-propylene oxide-ethylene oxide)) surfactant melts, resulting in the formation of well-ordered supramolecular assemblies with domain spacings ranging between 12.5 and 14.5 nm at additive loadings up to 40%. As the concentration of additives is increased, the general tendency is that the disordered system evolves into an ordered morphology and then undergoes an order-order transition before transitioning into a disordered phase, in one case. The scaling of interplanar spacing reveals that the additives are selectively incorporated in the poly(ethylene oxide) phase. Differential scanning calorimetry indicated that progressive increases in the loading of additives causes a decrease in the melting temperature and melting enthalpy of poly(ethylene oxide) crystallites. This behavior is consistent with good dispersion and strong interaction of the additives with the poly(ethylene oxide) phase. The principles invoked in this additive driven assembly process can be generally applied to the design of ordered functional BCP-nanoparticle hybrid materials while the specific materials described here could be of interest as etch masks.

Interaction Between Triblock Copolymer Surfactant and Low- κ Dielectric Surfaces Relevant to CMP

We examine the effects of the nonionic triblock copolymer surfactant Pluronic P103 on three surfaces of different wettability relevant to chemical mechanical planarization (CMP). Two of the surfaces are low-k organosilicate glass (OSG) films, Coral and Black Diamond; the third is a silica surface. Atomic force microscopy (AFM) force curves were used to probe the forces over each surface in solutions of P103. Each surface was also examined in potassium sulfate solutions to investigate the effect of ionic strengths. The AFM force curves show that both P103 and potassium sulfate eliminate adhesive forces at sufficiently high concentrations. DLVO theory was used to fit the AFM approach curves in order to calculate estimated surface potentials. Interestingly, the force curves suggest that molecular orientation of the P103 is different on surfaces of different wettability. The P103 was found to adopt a flat conformation on the hydrophilic silica surface while more extended structures formed on the more hydrophobic Coral and Black Diamond surfaces. These results provide a molecular-level understanding to aid the development of CMP formulations that will provide greater control on dielectric removal rate and reduce the overall non-uniformity in film thickness across the wafer.