Pluronic Surfactant Research Articles

Well Ordered Polymer Melts from Blends of Disordered Triblock Copolymer Surfactants and Functional Homopolymers

Addition of a functional homopolymer induces disorder-to-order transition in commercially available Pluronic surfactant melts. This approach may facilitate the use of amphiphilic surfactants in the industrial fabrication of structured nanomaterials.

Hexagonally ordered mesoporous highly acidic AlSBA-15 with different morphology: An efficient catalyst for acetylation of aromatics

Hexagonally ordered mesoporous AlSBA-15 with different n Si/ n Al ratios and morphology have been hydrothermally synthesized using the non-ionic copolymer Pluronic P123 surfactant as the structure directing agent and characterized by XRD, N 2 adsorption–desorption, SEM–EDX, elemental mapping, 27Al MAS NMR, and NH 3-TPD. It has been found that the shape and size of the particles can be controlled by the simple adjustment of the amount of Al content in the silica framework. Polygonal shaped particles with small (ca. 600 nm) and uniform size are observed for the AlSBA-15 materials with higher amount of Al in the framework. Acetylation of the aromatic compounds veratrole, anisole, and 2-methoxynaphthalene with acetic anhydride has been investigated over AlSBA-15 with different n Si/ n Al ratios under liquid phase conditions and the results are discussed. The activity of the AlSBA-15 catalysts in the acetylation of veratrole was found to increase with decreasing the n Si/ n Al ratio up to 45, and decreased with the further loading of Al in the framework. The effect of various reaction parameters such as reactant mole ratio, temperature, and catalyst concentration on the acetic anhydride conversion has been investigated in detail. The activity of the AlSBA-15 catalysts with different Al contents in the acetylation of veratrole was compared with various zeolite catalysts such as BEA, FAU, MOR, MFI, and AlMCM-41(22) where the number in parentheses denotes the n Si/ n Al ratio. It has been found that AlSBA-15 with the n Si/ n Al ratio of 45 showed the best performance in the acetylation of veratrole, with high acetic anhydride conversion and 100% selectivity to 3,4-dimethoxyacetophenone under the optimized reaction conditions. Moreover, the kinetics of the acetylation of veratrole over AlSBA-15 catalysts is discussed in detail.

Unusual behavior of PEG/PPG/Pluronic interfaces studied by a spinning drop tensiometer

The effects of surfactants on the interfacial tension driven retraction of elongated drops were studied in a spinning drop tensiometer. Experiments were conducted on polypropylene glycol (PPG) drops suspended in polyethylene glycol (PEG), with Pluronic block copolymers as surfactants. Two unusual observations are reported here. In the first, initially-elongated drops generated at high rotational speed were allowed to retract by reducing the rotational speed. Pluronic-laden drops would not retract completely, but would instead maintain strongly nonspherical shapes indefinitely. We attribute such “nonretraction” to an interfacial yield stress induced by the Pluronic surfactant. In the second, drops being heated while spinning at a constant speed would elongate sharply at some temperature, and subsequently breakup. Such “autoextension” and breakup indicate complex nonmonotonic changes in interfacial tension with time during heating. We propose that autoextension occurs because at low temperature, interfacially-adsorbed surfactant is crystallized and hence trapped at the interface at a concentration far above equilibrium.

Construction, Characterization, and Photoluminescence of Mesoporous Hybrids Containing Europium(III) Complexes Covalently Bonded to SBA-15 Directly Functionalized by Modified β-Diketone

Novel organic−inorganic mesoporous luminescent hybrid materials were prepared by linking the binary and ternary Eu3+ complexes to the functionalized ordered mesoporous SBA-15 with the modified 1-(2-naphthoyl)-3,3,3-trifluoroacetonate (NTA) by co-condensation of tetraethoxysilane (TEOS) in the presence of Pluronic P123 surfactant as a template. 1-(2-Naphthoyl)-3,3,3-trifluoroacetonate (NTA) grafted to the coupling agent 3-(triethoxysilyl)propyl isocyanate (TEPIC) was used as the precursor for the preparation of mesoporous materials. SBA-15 consisting of the highly luminescent ternary complex Eu(NTA)3bpy covalently bonded to the silica-based network, which was designated as Eu(NTA−SBA-15)3bpy, was obtained by introducing EuCl3 and 2,2‘-bipyridine (bpy) complex into the hybrid material via a ligand-exchange reaction. In addition, for comparison, SBA-15 doped with Eu(NTA)3·2H2O and Eu(NTA)3bpy complexes and SBA-15 covalently bonded with the binary Eu3+ complex with NTA ligand were also synthesized, denoted as...

Rheo-NMR of Wormlike Micelles Formed from Nonionic Pluronic Surfactants

Using a range of techniques combining rheology and magnetic resonance, we here investigate the flow and alignment properties of wormlike micelles formed by a 5% w/w solution of the BASF difunctional block copolymer nonionic surfactant, Pluronic P105 in water along with 4.3% w/v 1-phenylethanol-d5. A variety of shear-banding and alignment behaviors are observed, along with both stable and fluctuating flows. These strongly depend upon both temperature and applied shear rate. The deuterium-labelled alcohol enables study of alignment from quadrupole splitting, using a Hankel transform in the cylindrical geometry of our rheo-NMR cell.

Properties of Poly (L-lactic acid)/Pluronic Blends

Poly(L-lactic acid)(PLLA) and Pluronic surfactants (poly(ethylene oxide)(PEO)/poly(propylene oxide) (PPO) /poly(ethylene oxide)(PEO) triblock copolymer), with various compositions, were prepared by using the solventcast technique. Chloroform was used as a co-solvent. The effects of the addition of Pluronic on the properties of the PLLA film have been investigated with wide-angle X-ray diffraction, differential scanning calorimetry, in vitro degradation and gel permeation chromatography. As a result, we have the following conclusions : (1) the addition of Pluronic increases crystallinity of PLLA, (2) the addition of Pluronic influences the thermal properties of PLLA, and (3) the hydrolysis of PLLA/Pluronic blends depends on the composition of Pluronic. The decrease of the molecular weight of Pluronic or the increase of PEO contents in Pluronic components accelerates the hydrolysis of PLLA.

Synthesis of Fructone and Acylal Using Hexagonally Ordered Mesoporous Aluminosilicate Catalyst

Hexagonally ordered mesoporous AlSBA-15 with different nSi/nAl ratios have been hydrothermally synthesized using the non-ionic copolymer Pluronic P123 surfactant as the structure directing agent and characterized by XRD, N2 adsorption-desorption, and ammonia-temperature programmed desorption (pyridine-TPD). Acetal and acylal formation reactions of organic carbonyl compounds were efficiently catalyzed by AlSBA-15 under liquid-phase reaction conditions and the results were compared with the MFI, BEA and AlMCM-41(23). Of the catalysts studied, AlSBA-15(45) showed the highest activity in both the acetalization and acylal reactions of the carbonyl compounds under the optimized reaction conditions, and could be recycled several times without loss in activity. AlSBA-15(45) catalyst is highly stable, efficient, chemoselective, and environmental friendly, which could open the possibility for environment benign approach for the synthesis of acetals, acylals and its derivatives under mild reaction conditions.

Blue-light emission of mesoporous SBA-15 covalently bonded with carbazole chromophore

Much attention has been paid to carbazole derivatives for their potential applications as optical materials. For the first time, the blue-light-emitting carbazole chromophore has been covalently bonded to the ordered mesoporous SBA-15 (The resultant hybrid mesoporous materials are denoted as carbazole–SBA-15) by co-condensation of tetraethoxysilane (TEOS) and prepared compound 3-[ N-3-(triethoxysilyl)propyl]ureyl-9-ethyl-carbazole (denoted as carbazole–Si) in the presence of Pluronic P123 surfactant. The results of 1H NMR and Fourier transform infrared (FTIR) reveal that carbazole–Si has been successfully synthesized. Small-angle X-ray diffraction patterns (XRD) and Nitrogen (N 2) adsorption/desorption measurements were employed to characterize the mesostructure of carbazole–SBA-15. Solid-state 29Si magic-angle spinning (MAS) NMR was used to confirm the preservation of the carbazole group and estimate the degree of hydrolysis-condensation. Photoluminescence (PL) measurements show that carbazole–SBA-15(0.07) [carbazole–Si:(TEOS+carbazole–Si) molar ratio is 0.07] hybrid mesoporous material exhibits a monomeric emission in the “light blue” region with a PL quantum yield ∼31%. Compared with carbazole–Si, the I car/ C car (relative luminescence intensity divided by the content of carbazole) of carbazole–SBA-15(0.07) increases 24 times. The luminescence decays for 3-amino-9-ethyl-carbazole (denoted as carbazole–NH 2) and carbazole–Si are single-exponential functions of time, while those for carbazole–SBA-15 mesoporous materials are fitted by double-exponential functions. The stability studies on carbazole–Si and carbazole–SBA-15(0.07) show that the carbazole chromophore in the resultant hybrid mesoporous material exhibits better thermal stability than in carbazole–Si compound. The excellent luminescent properties and thermal stability enable the hybrid mesoporous material to have potential use as blue-light-emitting material in optical field.

Phase Behavior and Micellar Properties of Carboxylic Acid End Group Modified Pluronic Surfactants

The micellar behavior of three different carboxylic acid end standing (CAE) surfactants has been characterized using conductometry, differential scanning calorimetry, isothermal titration calorimetry, and dynamic light scattering. The CAE surfactants are modified high molecular weight Pluronic (PEO-PPO-PEO triblock copolymer) surfactants. The influence of pH and salt additives on the critical micellization temperature (CMT) and the cloud point of the CAE surfactants have been studied. Both the CMT and the cloud points of the CAE surfactants increase as a function of pH and decrease as a function of ionic strength. For the CAE surfactants, the CMT varies by about 5 degrees C, and the cloud point shows a variation in the order of 20-30 degrees C, as compared to the unmodified Pluronics. From the different experimental techniques, it follows that at low pH values (pH<3.5), the CAE surfactants show the same micellar behavior as the unmodified Pluronic, while at high pH values (pH>6), the micellar properties of the CAE surfactants are considerably different from those observed for the corresponding Pluronic. It has been demonstrated that the CAE micelles are capable of removing simultaneously divalent ions and phenanthrane. The CAE surfactants are the first known anionic surfactants that show cloud point behavior with the addition of low concentrations of simple salts, such as, for example, NaCl.

Preparation of amino-functionalized mesoporous silica thin films with highly ordered large pore structures

Highly ordered amino-functionalized mesoporous silica thin films have been directly synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) in the presence of triblock copolymer Pluronic P123 surfactant species under acidic conditions by sol-gel dip-coating. The effect of the sol aging on thin films organization is systematically studied, and the optimal sol aging time is obtained. The amino-functionalized mesoporous silica thin films exhibit a long-range ordering of 2D hexagonal (p6mm) mesostructure with a large pore size of 8.3 nm, a large Brunauer–Emmett–Teller (BET) specific surface area of 680 m2 g−1 and a large pore volume of 1.06 cm3 g−1 following surfactant extraction as demonstrated by X-ray diffraction (XRD), Transmission electron microscope (TEM), and physical adsorption techniques. Based on BET surface area and weight loss, the surface coverage of amino-groups for the amino-functionalized mesoporous silica thin films is calculated to be 3.2 amino-groups per nm2. Moreover, the functionalized thin films display improved properties for immobilization of cytochrome c in comparison with pure-silica mesoporous thin films.

Effect of process parameters on the synthesis of mesoporous nanocrystalline zirconia with triblock copolymer as template

Nanocrystalline zirconia powders with high surface area, mesoporous structure and tetragonal crystallite phase have been prepared by the surfactant-assisted route by using of Pluronic P123 block copolymer surfactant. The effect of several process parameters such as the type of zirconium precursor, pH value, refluxing time, refluxing temperature and surfactant to zirconium molar ratio on the structural properties of the powders have been investigated.

Synthesis of mesoporous nanocrystalline zirconia with tetragonal crystallite phase by using ethylene diamine as precipitation agent

Mesoporous nanocrystalline zirconia with high surface area and pure tetragonal crystallite phase has been prepared by bifunctional ethylene diamine as both precipitating agent for ZrO(NO3)2 to ZrO(OH)2 and colloidal protecting agent for the ZrO(OH)2 nanoparticles. The effect of refluxing time and temperature on the structural properties of the zirconia were investigated. The obtained results showed that the increasing in refluxing time and temperature improved the thermal stability and increased the tetragonal content of the zirconia. The results also showed that the addition of Pluronic P123 block copolymer surfactant acted as a cosurfactant and increased the specific surface area of the zirconia.

CO2−CH4 Reforming over Nickel Catalysts Supported on Mesoporous Nanocrystalline Zirconia with High Surface Area

Mesoporous nanocrystalline zirconia with a high surface area and pure tetragonal crystallite phase has been prepared by the surfactant-assisted route, using a Pluronic P123 block copolymer surfactant. The synthesized zirconia showed a surface area of 174 m2 g-1 after calcination at 700 °C for 4 h. X-ray diffraction and nitrogen adsorption analysis showed that the tetragonal phase and mesoporous structure were stable toward higher temperatures. The synthesized zirconia was employed as support for nickel catalysts for the production of syngas by dry reforming reaction. It was shown that the 5% Ni/ZrO2 catalyst exhibited stable activity for syngas production with a decrease of about 4% in methane conversion after 50 h of reaction. The addition of cerium oxide to the nickel catalyst improved its stability and decreased the coke deposition.

Stabilization of recombinant human growth hormone against emulsification-induced aggregation by Pluronic surfactants during microencapsulation

Protein aggregation upon exposing to the water/organic solvent interface is one of the most significant obstacles in developing poly(lactic- co-glycolic acid) (PLGA) microspheres with double emulsion process. The aim of present study is to devise a formulation strategy to prevent recombinant human growth hormone (rhGH) from aggregation during microencapsulation. The excipients used for stabilizing rhGH were selected from sugars, nonionic surfactants, polyol, and protein. Among the candidates, surfactants exhibited potentialities in protecting rhGH against emulsification-induced aggregation. It was also found that Pluronic F127 showed an outstanding as well as concentration-dependent stabilizing effect on rhGH, which was different to Pluronic F68 and Tween 20. After the rhGH solution comprising F127 and sucrose was emulsified with methylene chloride, the recovery of monomeric protein achieved 99.0%, principally attributed to the presence of F127. This solution was subsequently encapsulated as inner aqueous phase in the PLGA microspheres by a conventional double emulsion process, with the encapsulation efficiency higher than 98%. Improvement in the release of rhGH was observed for the microspheres co-encapsulating Pluronic F127 regardless in the presence or absence of sucrose, compared to the microspheres containing rhGH alone. The result further implied that co-encapsulation of Pluronic F127 in the microspheres played an important role in the stabilization of rhGH.

Topography in secondary ion mass spectroscopy images

Interpretation of time-of-flight secondary ion mass spectroscopy (TOF-SIMS) images from rough samples such as particles, fibers, or biological specimens can be problematic because the images are influenced not only by the sample chemistry but also by topographical features. In this article we have investigated the influence of spherical and cylindrical features on total ion yields, relative ion yields, and feature shape. TOF-SIMS images of Pluronic coated fibers and polystyrene spheres were collected using both triple focusing time and reflectron geometry instruments and a 25keV Ga+ primary ion source. The fibers and spheres were analyzed on both conducting and insulating substrates to assess the importance of field effects. Trends in the images have been explored using principal components analysis and Poisson and multinomial mixture models. The T2 test was employed to assess the statistical significance of results. The results identify three important topographic effects. The size and shape of features can be distorted as a result of the incidence angle of the primary ion beam. Additionally, both the absolute and relative intensities of ion peaks vary as a result of topography. In regions where the primary ion beam impacted the sample at a glancing angle, the relative intensity of molecular fragments characteristic of the Pluronic surfactant was up to three times higher than in regions where the beam impacted the sample at a normal angle. Comparison of results from conducting and insulating samples suggests that changes in the relative ion yields resulted primarily from differences in the incidence angle of the primary ion beam while changes in the total ion yield are influenced by both the incidence angle and distortion of the electric field by the particle. This study documents that topographic features can influence not only the absolute intensity of ion peaks but can also alter peak ratios in a statistically significant manner. In this light, a greater degree of caution is recommended when interpreting TOF-SIMS images from topographically complex samples.

SIMS depth profiling of polymer blends with protein based drugs

We report the results of the surface and in-depth characterization of two component blend films of poly( l-lactic acid) (PLLA) and Pluronic surfactant [poly(ethylene oxide) (A) poly(propylene oxide) (B) ABA block copolymer]. These blend systems are of particular importance for protein drug delivery, where it is expected that the Pluronic surfactant will retain the activity of the protein drug and enhance the biocompatibility of the device. Angle dependant X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) employing an SF 5 + polyatomic primary ion source were both used for monitoring the surfactant's concentration as a function of depth. The results show an increased concentration of surfactant at the surface, where the surface segregation initially increases with increasing bulk concentration and then remains constant above 5% (w/w) Pluronic. This surface segregated region is immediately followed by a depletion region with a homogeneous mixture in the bulk of the film. These results suggest the selection of the surfactant bulk concentration of the thin film matrices for drugs/proteins delivery should achieve a relatively homogeneous distribution of stabilizer/protein in the PLLA matrix. Analysis of three component blends of PLLA, Pluronic and insulin are also investigated. In the three component blends, ToF-SIMS imaging shows the spatial distribution of surfactant/protein mixtures. These data are reported also as depth profiles.

A Pluronic-coupled metal-chelating ligand for membrane affinity chromatography

A technique for bio-specific affinity chromatography using synthetic nonporous membranes and a new metal-chelating Pluronic surfactant is described. Synthetic polymeric poly(vinyldiene fluoride) membranes were fabricated for use as solid, hydrophobic adsorption membrane matrices. An ethylene diamine tetraacetic acid dianhydride was coupled to the terminal hydroxyl end groups of Pluronic ® F108 via a two-step reaction at 40 °C, to create a new metal affinity ligand, Pluronic- N,N-dicarboxymethyl-3,6-diazaoctanedioate (Pluronic-DMDDO). The hydrophobic poly(propylene oxide) moiety of Pluronic allowed non-covalent adsorption of the ligand to the hydrophobic membrane matrix. The protein repellent properties of the hydrophilic poly(ethylene oxide) brush layer of Pluronic, served to preserve the bio-specific activity of the ligand and to increase ligand accessibility. Proton-induced X-ray emission (PIXE) analysis was used to determine the metal binding capacity, stability and surface homogeneity of this immobilised metal affinity membrane system and to generate surface homogeneity maps of the chelated metal ions. The chelate capacity of Pluronic-DMDDO was determined under non-competitive conditions and was of the order (Zn 2+ > Ni 2+ > Cu 2+). An amino terminal hex-histidine-tagged recombinant Escherichia coli pantothenate kinase was used as a test protein. Histidine-tagged pantothenate kinase bound strongly to Pluronic-DMDDO-treated membranes specifically in the presence of Ni 2+. Eluted immobilised histidine-tagged proteins retained their biochemical activity and the membranes were capable of being regenerated and re-used.

Anionic surfactant induced mesophase transformation to synthesize highly ordered large-pore mesoporous silica structures

Successive mesophase transformation induced by an anionic surfactant such as sodium dioctyl sulfosuccinate (AOT) has been demonstrated to fabricate four kinds of large pore mesoporous silica materials in a triblock copolymer F127 surfactant assembly system. The transformation of the highly ordered mesostructures from face-centered cubic (space group Fmm) to body-centered Imm then towards two-dimensional (2-D) hexagonal p6m and eventually to cubic bicontinuous Iad symmetries has been achieved by tuning the amount of AOT and 1,3,5-trimethylbenzene (TMB). Characterization by small-angle X-ray scattering (SAXS), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2 sorption isotherms reveals that all mesoporous silica structures have highly ordered regularity in large domains and possess high surface areas, large pore volumes and uniform pore sizes. The expansion of hydrophobic volume in the amphiphilic Pluronic F127 surfactant associated with AOT and TMB molecules in an acidic media is attributed to the observed mesophase transformation. A further swelling of the surfactant micelles can be achieved by adding TMB molecules into the mixed AOT and F127 surfactants system due to their synergistic solubility enhancement, which gives rise to a long-range ordered 2-D hexagonal mesoporous silica structure with very large cell parameter (a = 16.5 nm) and pore size (∼12 nm). The understanding of the blend–surfactant assembly mechanism will lead to a more rational approach for economical and large-scale production of mesoporous materials with controllable structures.

Cover Picture: Self‐Assembly of Single‐Walled Carbon Nanotubes into a Sheet by Drop Drying (Adv. Mater. 1/2006)

AbstractDrops of a suspension of individual single‐walled carbon nanotubes in F68 Pluronic surfactant dry on glass substrates to form a “crust” at the free surface. The crust is extremely thin (∼ 100 nm) and consists of an entangled mesh of nanotubes and Pluronic. Pasquali and co‐workers report on p. 29 that the convective flow associated with the drying preferentially assembles the micelles into a hexagonal arrangement, as revealed by the birefringent pattern shown on the cover. This technique is promising for developing thin, optically transparent, and electrically conductive coatings and films consisting of nanotubes.

Novel Mesoporous Mixed Nb−M (M = V, Mo, and Sb) Oxides for Oxidative Dehydrogenation of Propane

Novel thermally stable mesoporous mixed metal Nb-M (M = V, Mo and Sb) oxides were synthesized in the presence of a nonionic Pluronic P123 surfactant. These oxides displayed promising pore structures and chemical compositions for selective oxidative functionalization of propane: high surface areas (up to 200 m2/g), large pore sizes (5-14 nm), and high pore volumes (up to 0.46 cm3/g). The oxidative dehydrogenation of propane to propylene over mesoporous mixed metal Nb-M oxides employed as a probe reaction suggested that the M component was dispersed as the molecular surface species and also formed a solid solution with NbOx in the inorganic walls of these mesoporous mixed metal oxides.