Poly Oxyethylene Block Research Articles

Demulsifier-Inspired Superhydrophilic/Underwater Superoleophobic Membrane Modified with Polyoxypropylene Polyoxyethylene Block Polymer for Enhanced Oil/Water Separation Properties.

Demulsifiers are considered the key materials for oil/water separation. Various works in recent years have shown that demulsifiers with polyoxypropylen epolyoxyethylene branched structures possess better demulsification effects. In this work, inspired by the chemical structure of demulsifiers, a novel superhydrophilic/underwater superoleophobic membrane modified with a polyoxypropylene polyoxyethylene block polymer was fabricated for enhanced separation of O/W emulsion. First, a typical polyoxypropylene polyoxyethylene triblock polymer (Pluronic F127) was grafted onto the poly styrene-maleic anhydride (SMA). Then, the Pluronic F127-grafted SMA (abbreviated as F127@SMA) was blended with polyvinylidene fluoride (PVDF) for the preparation of the F127@SMA/PVDF ultrafiltration membrane. The obtained F127@SMA/PVDF ultrafiltration membrane displayed superhydrophilic/underwater superoleophobic properties, with a water contact angle of 0° and an underwater oil contact angle (UOCA) higher than 150° for various oils. Moreover, it had excellent separation efficiency for SDS-stabilized emulsions, even when the oil being emulsified was crude oil. The oil removal efficiency was greater than 99.1%, and the flux was up to 272.4 L·m-2·h-1. Most importantly, the proposed F127@SMA/PVDF membrane also exhibited outstanding reusability and long-term stability. Its UOCA remained higher than 150° in harsh acidic, alkaline, and high-salt circumstances. Overall, the present work proposed an environmentally friendly and convenient approach for the development of practical oil/water separation membranes.

Multifunctional Polymer Nanocarrier for Efficient Targeted Cellular and Subcellular Anticancer Drug Delivery.

A multifunctional triblock copolymer intended for targeted drug delivery applications has been designed and successfully synthesized. Following various controlled polymerization and modification steps, a saccharide end-functionalized polyoxyethylene block was attached through an aromatic imine bond, cleavable in slightly acidic conditions, to an amphiphilic diblock copolymer comprising abiodegradable hydrophobic block and a partially modified with mitochondria targeting ligands polycationic block. The micelles formed from the triblock copolymer in aqueous media possess key functions (cleavable "stealth" shield, targeting groups) needed for safe extracellular transport, successful cell internalization, and drug delivery to the target cellular organelles. The multifunctional nanocarriers were loaded with the plant-derived anticancer drug curcumin, and in vitro analyses revealed that their cytotoxic, apoptogenic, and NF-κB-inhibitory effects on target cells were superior over those of the free drug and non-functionalized polymer micelles of similar composition. Moreover, the enhanced cellular internalization and mitochondrial accumulation of the multifunctional nanocarriers compared to their non-functionalized analogues was visualized by fluorescence microscopy. The results indicate that the presented multifunctional micelles have a potential for application in nanomedicine for enhanced organelle-specific drug delivery.

SANS study on influence of temperature on nanophase separation in epoxy-based hydrogels

Effect of temperature on nanophase separated structure of epoxy-based hydrogels containing polyoxyethylene (POE), polyoxypropylene (POP) and diglycidyl ether of Bisphenol A propoxylate (PDGEBA) was studied using small-angle neutron scattering (SANS). At the macroscopic level, increase of temperature causes an expulsion of water from the hydrogels. At the microscopic level, the expulsion of water is accompanied by redistribution of water and POE inside the hydrogels. Two kinds of structure have been revealed in the hydrogels by SANS. The structure with shorter characteristic length measured by Bragg’s distance (ca 70–80Å) is observed in all hydrogels and at all investigated temperatures (5–80°C). It is attributed to a distribution of water into water-rich and water-poor domains caused by nanophase separation of the crosslinked system due to differences in interaction of individual network building blocks with water. The water-rich domains consist of a part of POE blocks mixed with water. The water-poor domains consist of POP and PDGEBA blocks mixed with a small amount of water and remaining POE blocks. The domains are separated by a diffuse interface with effective thickness ca 7–10Å as estimated from deviations from Porod’s law. Formation of a new structure with longer characteristic length (ca 240Å) is observed in the highly non-stoichiometric hydrogels. Its contribution to SANS becomes more pronounced with increasing temperature. This contribution is attributed to the formation of regions of pure water (water pools) as a new hydrogel phase that is enabled by low network density and high amount of pending chains in the highly non-stoichiometric epoxy networks subject to swelling.

Synthesis and characterization of siloxane photopolymers used for microfluidic devices

Synthesis and characterization of a PCR acceptable diacrylic macromer composed of a siloxane block and two polyoxyethylene blocks.

Binary Phase Diagram of Water/Brij58 Studied by SAXS

Laboratoire de Physique de l’Etat Condense, UMR CNRS 6087, Universite du Maine 72085 Le Mans Cedex 09, France The phase diagram of the binary water/Brij58 system has been studied at constant temperature T = 20 ◦C first by simple optical observation and then by small angle X-ray scattering. The small angle X-ray scattering patterns in the isotropic diluted phase are analyzed in a quantitative way by refining the experimental measurements with a model assuming hard spherical micelles in interaction. The micelles are described by a poly dispersed core-shell model and the interaction by the Perkus–Yevick hard-sphere model. The fitted parameters are analyzed in detail to determine the way polyoxyethylene blocks are hydrated with respect to the volumic fraction of water. In the more concentrated regime, the crystalline phases that are identified are the Fm3m cubic, the 2D hexagonal and the lamellar phases. The structural parameters that describe each phases are analyzed and commented. The small angle X-ray scattering study is complemented by the determination of the temperature dependent liquid–solid transition by rheology.

New Polymer Matrices for Chemical Optical Sensors

New comb-shaped polymers containing side polyoxyethylene blocks were synthesised. For the case of model compounds, the possibility of using the polymers obtained as matrices of chemical optical sensors was assessed. The influence of the length and number of block substituents on the swelling of the polymers in water was investigated. Almost 100% binding of the model compounds by the polymer matrix was observed, and also the practically complete absence of hydrolysis of the model compounds for 1 h. The conducted investigations showed the promise of using the polymers obtained as matrices for chemical optical sensors.

Synthesis of new poly(ethylene glycol)-block-poly(ester sulfide) dendrimers

The design and synthesis of novel copolymers that consist of a linear polyoxyethylene block and a dendrimeric poly(ester-sulfide) block with potential applications in drug delivery are described. The dendrimers bear hydroxyl or acrylate functional groups and were prepared via a divergent approach using readily available methoxypoly(ethylene glycol) (mPEG), acryloyl chloride, and 1-thioglycerol as building blocks. All reactions involved occurred efficiently and purification steps consisted of washing the reaction mixture with aqueous solutions and precipitation of the product in diethyl ether.

Synthesis of polyoxyethylene block copolymers and their aggregation in water

The possibility of thermal degradation of polyoxyethylene in the course of high-temperature polycondensation was examined. Conditions were suggested for the low-temperature synthesis of ABA block copolymers whose molecules contain a polyoxyethylene central block and p-aromatic ester terminal blocks. The aggregation of the block copolymers in water was studied by dynamic light scattering and electron microscopy.

Cosolvent Effects on the Micellization of Oxyphenyl(copoly)ethylene Oxide Copolymers in Aqueous Solution

In the present paper, we have analyzed how the presence of ethanol affects the micellization process of two structurally related polyoxyethylene block copolymers with diblock and triblock architectures (diblock, S15E63; triblock, E67S15E67) and the same hydrophobic block length, formed by oxyphenylethylene units, through surface tension, static and dynamic light scattering, density, ultrasound velocity, transmission electron microscopy, and steady-state fluorescence techniques. E and S denote the oxyethylene (-OCH2CH2) and oxyphenylethylene (-OCH2CH(C6H5)) units, respectively, and the subscripts the block length. The effect of increasing amounts of ethanol in solution gives rise to a progressive disruption of the micelle structures formed by these copolymers, with an increase in the critical micelle concentration (cmc) values and a decrease in the micellar aggregation number. This originated from the deswelling of the poly(ethylene oxide) (PEO) chains due to a decrease of the water content, accompanied by a reduction of the solvophobicity and an increase of the solubility of the S blocks, causing the lowering of the interfacial tension between the polyoxyphenylethylene core and the solvent, and favoring the swelling of hydrophobic blocks. Therefore, to achieve thermodynamic equilibrium, the micelle size should be smaller. A model derived from small angle neutron scattering (SANS) data is also applied to get extra information on micelle structure. With the aim of obtaining information about the hydration of micellar solutions of these block copolymers, compressibility and fluorescence data were collected. The increase of compressibility with ethanol addition confirms the swelling of the hydrophobic polyoxyphenylethylene chains. Fluorescence data show that the addition of ethanol to the solution decreases the polarity, favoring the solubilization of the oxyphenylethylene chains in the mixed solvent as single monomers. Aggregation data derived from this technique are in fair agreement with those obtained from light scattering.

Direct Force Measurement of Silicone- and Hydrocarbon-Based ABA Triblock Surfactants in Alcoholic Media by Atomic Force Microscopy

The surface force profiles between an atomic force microscopy (AFM) tip and a self-assembled monolayer of n-octadecyltrichlorosilane on oxidized silicon were measured in an ABA triblock series of silicone and Pluronic surfactant solutions. Changes in steric force barrier thickness and height were examined as a function of hydrophobic and hydrophilic block size and ethanol to water ratio in mixed solvents. In water, all the surface force profiles exhibited repulsive forces except for the Pluronic surfactants with short polyoxyethylene blocks. The steric barrier thickness increased with increasing hydrophilic block size, with an estimated force decay length proportional to (number of oxyethylene units) 0.62. However, the same data yielded no clear correlation between the hydrophobic chain block size and the steric barrier. The silicone surfactants provided steric repulsion up to 80% ethanol in solution, while the Pluronic surfactants lost their surface activity at approximately 40% ethanol in solution. The difference between the Pluronic surfactants and the silicone surfactants is attributed to the polysiloxane block being hydrophobic as well as oleophobic. In addition, the solubility and surface activity of silicone surfactants in alcoholic media are tunable by the ratio of oxyethylene to oxypropylene units.

Investigation of relaxations in polystyrene–polyoxyethylene copolymer by thermally stimulated current

The diblock copolymer containing 43.5 wt.% of polystyrene (PS) (M w =15 000) and polyoxyethylene (POE) (M w =19 500) was investigated by integral and by partial thermally stimulated depolarization current (TSDC) measurements in the temperature range of 173–293 K. The first peak P 1, widely distributed from 183 to 213 K, was a dipolar peak attributed to the initial stage of glass transition in POE. The second peak P 2, with a maximum at 273 K, was due to glass transition. The third peak P 3, with a maximum at about 263 K, was caused by the space charge relaxation localized at the interfaces between the ordered and nonordered phases in POE, Maxwell–Wagner relaxation, representing a precursor in melting of POE crystals. The results were supported by determination of activation energy E a of the partial peaks, which covered the whole range of investigation, and by differential scanning calorimetry (DSC) measurements. The E a( T) distribution showed a maximum in entropy change at 219±4 K. Some runs with samples containing different amounts of the PS component were considered. All the relaxations were coming from the POE block. The current due to PS slightly overlapped the total spectra without interaction. The influence of the repeated runs was observed and discussed.

Contrasts in the surface activity of polyoxypropylene and polyoxybutylene‐based block copolymer surfactants

AbstractPrevious studies have shown that polyoxybutylene surfactant hydrophobes are less polar than polyoxypropylene hydrophobes. Polyoxyalkylene hydrophobes can be modified by ethoxylation to give terminal polyoxyethylene block hydrophilic groups. Polyoxybutylene/polyoxyethylene copolymer surfactants exhibit differentiated interfacial tensions, and wetting and foaming properties when compared to structurally equivalent polyoxypropylene/polyoxyethylene copolymers. There have been no reported comparisons, however, of polyoxybutylene/polyoxyethylene copolymers and polyoxypropylene/polyoxyethylene analogues in terms of fundamental parameters, such as critical micelle concentration, area per molecule at the interface, efficiency, and effectiveness. In one phase of this work, four polyoxybutylene/polyoxyethylene block copolymer surfactants were compared to structurally analogous polyoxypropylene/polyoxyethylene materials. Findings showed that polyoxybutylene/polyoxyethylene copolymers exhibited enhanced cotton wetting and lower surface and interfacial tensions compared to polyoxypropylene/polyoxyethylene analogues. Polyoxybutylene‐based surfactants were typically one order of magnitude better in their ability to reduce surface tension at interface saturation. Polyoxybutylene/polyoxyethylene copolymers pack more efficiently at the interface, as evidenced by a smaller area per molecule at the interface. Critical micelle concentration values were also lower for polyoxybutylene/polyoxyethylene copolymers. A second phase of experiments focused on the surface activity of polyoxypropylene/polyoxyethylene triblock copolymers with higher molecular weight hydrophobes. Enhanced surface activity was found when compared to lower‐molecular weight polyoxypropylene/polyoxyethylene copolymers.

Gas transport properties of siloxane polyurethanes

AbstractPolyurethanes (PUs) were synthesized from toluenediisocyanates (TDIs) and a polymeric diol having polydimethylsiloxane and polyoxyethylene blocks of the ABA type, ended with OH groups. Prepolymers, prepared in toluene solution using ratios [NCO]/[OH] ≥ 2, were crosslinked with triisopropanolamine (TIPA) (ratio [OH]/[NCO] = 1.1) (two‐step process). PUs were also obtained with a one‐step process using, contemporaneously, TDI, block copolymer, and, as crosslinking agent, TIPA or the glyceride of ε‐hydroxyhexanoic acid. Polydimethylsiloxane (PDMSO) was prepared as a reference material. The course of the reaction between block copolymer and TDI was studied by differential scanning calorimetry in the absence and presence of benzoyl chloride (BzCl). Without BzCl, with ratios [NCO]/[OH] > 2, uncontrolled crosslinking side reactions occur. The properties of the PU films obtained with the two methods were studied both for the density of crosslinking and for gas transport properties. The two‐step polymers are less crosslinked than the others and are characterized by higher diffusion coefficients and by higher permeability to gases. The permeability order is 10−9 (N cm3 cm−1 cm−1 cm Hg−1 s−1) for CH4, O2, CO, and N2 and is 10 times higher for CO2. The selectivity for the couple O2/N2 is higher than that obtained with PDMSO films. Considerable selectivities are shown for the couples CO2/N2 and CO2/CO. © 1995 John Wiley & Sons, Inc.

Effects and measurements of polyoxyethylene block length in polyoxyethylene‐polyoxybutylene copolymers

Block copolymer surfactants, made from 1,2-butylene oxide (BO), propylene oxide (PO) and ethylene oxide (EO), exhibit wide ranges of properties and performance. In particular, BO/EO block copolymers exhibit improved surfactant performance with respect to PO/EO analogs. One interesting difference between these two classes of surfactants is the EO capping efficiency of polyoxypropylene (POP) vs. polyoxybutylene (POB) hydrophobe secondary hydroxyl groups. In this regard, nuclear magnetic resonance measurements have shown that POP secondary diols react more readily with EO than POB diols. For the case of ethoxylated POB polymers, the amount of unethoxylated secondary hydroxyl is proportional to the average length of the polyoxyethylene (POE) blocks. Differential scanning calorimetry was used to observe crystallinity of POE blocks. For a given POB hydrophobe molecular weight and weight percentage EO, surfactant performance properties can be augmented by affecting POE block length in the ethoxylation process.

Facilitated permeation of myoglobin through porous membranes: Different permeation behavior through membranes of polyoxyethylene‐ and dextran‐conjugated polyamides prepared by quasi‐living polymerization of a bicyclic lactam

AbstractIn the ultrafiltration test of a myoglobin solution through porous membranes of the ABA‐type block copolymers composed of polyamide as outer segments and polyoxyethylene (Mn = 1.9–2.0 × 104) as an inner segment, in which the values of weight fraction of the polyamide segments (W) were 0.90, 0.84, 0.82, 0.81, and 0.73, the concentration of the permeate was found to be much higher than that in feed under the pressure difference of 1–2 kg/cm2. Such singularly facilitated permeation was observed also in the test through the dense membranes of the polyamide–polyoxyethylene block copolymer with W of 0.81 and 0.73. On the other hand, neither porous nor dense membranes of the graft copolymer (W = 0.83) having a dextran stock (Mn = 1.8 × 104) and 2.6 pieces of polyamide branches showed similar facilitated permeation, although dextran was soluble in water as well as polyoxyethylene. The apparent interaction of myoglobin with dextran may be stronger than that with polyoxyethylene. © 1994 John Wiley & Sons, Inc.

Effects and measurements of polyoxyethylene block length in polyoxyethylene‐polyoxybutylene copolymers

AbstractBlock copolymer surfactants, made from 1,2‐butylene oxide (BO), propylene oxide (PO) and ethylene oxide (EO), exhibit wide ranges of properties and performance. In particular, BO/EO block copolymers exhibit improved surfactant performance with respect to PO/EO analogs. One interesting difference between these two classes of surfactants is the EO capping efficiency of polyoxypropylene (POP) vs. polyoxybutylene (POB) hydrophobe secondary hydroxyl groups. In this regard, nuclear magnetic resonance measurements have shown that POP secondary diols react more readily with EO than POB diols. For the case of ethoxylated POB polymers, the amount of unethoxylated secondary hydroxyl is proportional to the average length of the polyoxyethylene (POE) blocks. Differential scanning calorimetry was used to observe crystallinity of POE blocks. For a given POB hydrophobe molecular weight and weight percentage EO, surfactant performance properties can be augmented by affecting POE block length in the ethoxylation process.

Formation and Characterization of Cyclosporine-Loaded Nanoparticles

The commercially available formulations of cyclosporine (cyclosporin A, CyA) are associated with acute hemodynamic changes that result in high nephrotoxicity. Among colloidal vectors, nanoparticles (NPs) are receiving much attention as potential drug carriers that would avoid the therapeutic risks of conventional formulations. Two different mechanisms for obtaining polymeric NPs loaded with CyA were studied with regard to their preparation and physicochemical characterization. lsobutyl-2-cyanoacrylate monomer (IBCA) was polymerized, whereas poly-E-caprolactone (PCL, a preformed polymer) was precipitated; both reactions took place in an aqueous medium containing Pluronic F-68 (polyoxypropylene polyoxyethylene block copolymer) as a surface active agent. The encapsulation efficiencies were 78.49 ± 5.87 and 84.85 ± 5.02%, respectively, and they remained stable over a wide range of drug concentrations. The polymeric NP had average sizes of 81 ± 25 and 95 ± 25nm for poly-IBCA and PCL, respectively, as confirmed by photon correlation spectroscopy. Poly-IBCA NPs were built from oligomers with molecular weights of 157 to 2644 that joined to form a polymeric nanomatrix. In vitro activity of the drug and the carrier was tested by inhibition of lymphocyte proliferation induced by Concanavalin A. Drug-loaded PCL NPs and free CyA inhibited lymphocyte proliferation by 91.40 and 86.19%, respectively. However, drug-free NPs also exhibited statistically significant (p < 0.05) immunosuppressive activity.

Synthesis of polystyrene‐block‐polyoxyethylene for use as a stabilizer in the emulsion polymerization of styrene

AbstractFive well‐defined polystyrene‐block‐polyoxyethylene copolymers were synthesized by anionic polymerization for use as stabilizers in the emulsion polymerization of styrene. The size of the blocks and their relative weight ratios to each other were the main variables. The molecular weights of the blocks varied from M̄n = 1000–7000 for polystyrene, and M̄w = 3000–9000 for polyoxyethylene. The results of the styrene emulsion polymerization with these block copolymers as stabilizers indicate that for efficient anchoring the block length need not be more than 10 monomer units, possibly even less, and that the polyoxyethylene block M̄w = 3000 is just as capable of stabilizing the polystyrene particle as the higher molecular weight blocks. A very important factor was found to be the weight ratio of the two blocks: block copolymers with a polyoxyethylene content between 75 and 90 wt % were effective stabilizers for the emulsion polymerization of styrene © 1992 John Wiley &amp; Sons, Inc.

The aggregation behavior of poly-(oxyethylene)-poly-(oxypropylene)-poly-(oxyethylene)-block-copolymers in aqueous solution

Aqueous solutions of blockcopolymers, consisting of a polyoxypropyleneblock (POP) with a polyoxyethylene-block (POE) at each side, were studied using surface and interfacial tension measurements, static and dynamic light scattering and smallangle neutron scattering techniques, electric birefringence, rheological and DSC-measurements. The compounds were commercial samples and had an approximate average composition EO20PO70EO20, EO18PO58EO18, and EO106PO69EO106. All three compounds formed micelles above a critical concentration. The size of the micellar core is determined by the length of the hydrophobic poly-propyleneoxide block. The transfer energy of a propyleneoxide unit from the aqueous to the micellar phase is about 0.3 kT at room temperature and hence a quarter of the corresponding value for a CH2-group.

Perfluoroalkylated sucrose, trehalose, maltose and glucose derivatives: surfactants for biomedical uses

New neutral F-Alkylated surfactants have been synthesized and evaluated, the objectives being to improve the stability of fluorocarbon emulsions to be used as injectable O2-carriers and gain improved control over their biologically relevant characteristics.A series of mono- and diesters of sucrose (1,2)and trehalose (3,4) was prepared using Mitsunobu's condensation procedure (R1-R4 = H or CnF2n+1(CH2)mC(O)). ▪New perfluoroalkylated glycosides were obtained using the Koenigs-Knorr reaction : ▪5,6 : m = 3, 9, RF = C6F13; m = 9, RF = C8F17. 7 : R5 = MeC(O), RF = C6F13, C8F17; R5 = per-O-acetyl-α-D-glucopyranosyl, RF = C6F13. 8 : RF = C6F17. 9, 10 : R6 = H, α-D-glucopyranosyl, RF = C6F13.The surface activity of the new compounds was measured (γs, γ i/F-decalin, CMC). The F-alkylated maltosides were found to be particularly efficient as cosurfactants in conjunction with a polyoxypropylene polyoxyethylene block polymer (Pluronic F-68).