Ethylene Oxide Triblock Copolymer Research Articles

Worm-like micelles of triblock copolymer of ethylene oxide and styrene oxide characterised using light scattering and Taylor dispersion analysis.

A triblock ESE copolymer (E16S8E16, S=styrene oxide and E=ethylene oxide) was synthesised by sequential oxyanionic copolymerisation of styrene oxide followed by ethylene oxide. Light scattering studies demonstrated a shape transition from spherical micelles to worm-like micelles above a critical temperature of approximately 18°C. Taylor dispersion analysis (TDA) also indicated a size growth when the temperature increased from 25 to 40°C due to the formation of worm-like micelles. The hydrodynamic radii and diffusion coefficients obtained by these two techniques were in good agreement. The solubility of a hydrophobic drug, terfenadine, in dilute micellar solutions of the copolymer was increased at least 20-fold under the conditions. The transition to worm-like micelles at raised temperatures led to enhanced solubilisation capacities due to a larger hydrophobic core volume. The behaviour of the novel ESE copolymer shows the utility of TDA to follow conformational changes using nanolitre quantities and explore critical quality attributes for this type of drug delivery system.

Rouse dynamics in PEO-PPO-PEO block-copolymers in aqueous solution as observed through fast field-cycling NMR relaxometry

We present a proton fast field-cycling (FFC) NMR relaxometry study of the molecular dynamics in three different deuterated water-dispersed triblock copolymers of ethylene oxide (EO) and propylene oxide (PO):EO80PO27EO80(F68), EO141PO44EO141 (F108), and EO101PO56EO101(F127). Independently of the phase and molecular arrangement, bi-exponential decays of the magnetization during the spin-lattice relaxation process could be observed for F127, while mono-exponential decays were measured for F68 and F108. This fact has been attributed to the relative ratio of PEO and PPO protons for each case. In F127, each component of the magnetization decay could be associated with a particular block of the co-polymer. A direct consequence of this fact is the independent characterization of the molecular dynamics of each block. It was found that the dominant relaxation mechanism can be attributed to the Rouse model, and it seems to be independent on whether the molecules are incorporated into a micelle, or as individual unimers in the aqueous solution. The experimental results and the provided explanation are consistent with entanglement-free self-assembled structures, and a fast exchange of unimers between the micellar structure and the solvent. This particular feature was also investigated in F68 and F108, although for these cases a mono-exponential decay of the magnetization was observed. NMR relaxometry results are complemented with other relaxation experiments in the rotating frame, NMR spectroscopy and atomic-force microscopy.

Effect of metal-free porphyrins on the thermal–oxidative breakdown of biocompatible polymers

The inhibitory effect of metal-free porphyrins on the thermal–oxidative breakdown of several biocompatible polymers is observed for the first time. Differential thermal analysis shows that the thermal stability of poly(ethylene oxide) and triblock copolymers of ethylene oxide and propylene oxide increases by 80–100 K, compared to the initial breakdown temperatures of these polymers in the presence of metal-free porphyrins (up to 3 wt %).

Thermally Responsive Composite Hydrogel via Self-Assembly for Smart Window Applications

A novel thermally responsive hydrogel (TRH) has been demonstrated by confining poly(ethylene oxide), poly(propylene oxide), and poly(ethylene oxide) triblock-copolymer (EPE) molecules into the pores of polymer framework. Aqueous EPE copolymer molecule had a tendency to aggregate to form clusters gradually and precipitated from water when the temperature is above a cloudy point. By adding EPE molecules into the acrylamide (AM) monomer solution, the mixture can be fabricated as uniform and transparent hydrogel via controlled radical polymerization. The polyacrylamide hydrogel is produced with a switchable optical property when subjecting to temperature variation. Such reversible thermally responsive material can be utilized as a functional material for smart window application. Additionally, the thermal responsive hydrogel is an inexpensive material, which is readily applicable as smart windows with significant reduction in material cost.

Activation Thermodynamics and Concentration Scaling of the Viscosity of Unimeric and Aggregated Poloxamer EO93PO54EO93 in Water

The viscosity of the aqueous solutions of Poloxamer EO93PO54EO93 (a triblock copolymer of ethylene oxide, EO, and propylene oxide, PO) was determined at concentrations ranging from 0.002 to 0.12 g·mL–1 at 0.9, 8.9, and 20.0 °C where only unimers are present, at 24.9 and 30.3 °C where the unimers are in equilibrium with aggregates and at 39.8 and 49.8 °C where only aggregates are present. The reciprocal of the intrinsic viscosity derived from Huggins, Kraemer, Martin and Phillies’s models is compared to the experimentally determined overlap concentration. A simple model that accounts for intermolecular interactions provides better estimates of the experimental overlap concentration. The concentration scaling exponents of the viscosity at low and high concentrations are compared to the predictions for entangled polymer chains. It is suggested that at low temperature, the Poloxamer molecules evolve from dilute unimers to semidilute unentangled unimers. At high temperature, Poloxamer molecules evolve from dil...

Investigation of suppressor polyethylene glycol dodecyl ether on electroplated Cu filling by electrochemical method

In this paper, the use of polyethylene glycol dodecyl ether (POE) with a molecular weight of 1200 (POE-1200) as a suppressor for bottom-up electroplated copper filling of microvias was investigated. Galvanostatic measurement indicated that POE-1200 had much stronger suppression for Cu electrodeposition than PEG-8000 (polyethylene glycol with a molecular weight of 8000) and EPE-8000 (triblock copolymers of ethylene oxide–propylene oxide–ethylene oxide with a molecular weight of 8000). The strong synergistic suppression between POE-1200 and Cl− led to a very thin surface thickness and excellent filling performance of microvias. The cross-sectional observations of the microvias after electroplated confirmed that changing the POE-1200 concentration from 20 to 700 ppm had little effect on the filling performance because of an unchanged positive potential difference. The adsorption strength of POE-1200 on the cathode surface was enhanced greatly only in the presence of Cl− , attributing to a formation of Cl− –Cu+–POE-1200 complex. The critical adsorption concentration of Cl− and POE-1200 to form a saturated barrier film on the electrode surface was studied by Cu stripping peaks of cyclic voltammetry curves. In addition, the relationship between the saturated barrier of Cl− –Cu+–POE-1200 complex and the filling performance has been proposed.

The influence of temperature on the photo-oxidation rate of tryptophan in the presence of complexes of porphyrins with amphiphilic polymers**This work was supported by the Russian Foundation for Basic Research (project nos. 13-02-12422ofim and 13-02-00934).

The influence of temperature on the photocatalytic activity of the complexes of water-soluble porphyrin photosensitizers with amphiphilic polymers, such as poly-4-vinylpyrrolidone, polyethylene oxide, and Pluronic F127 (triblock copolymers of ethylene oxide and propylene oxide) in photo-oxidation reaction of tryptophan in the aqueous solution has been investigated. It has been shown that in the temperature range of 10–40 °C the addition of these polymers increases the activity of triglucamine salt of chlorine e6, tertrasodium salt of tetrasulfophenilporfirina and dimegin. The greatest influence on the rate of photo-oxidation appears to be rendered by the introduction of poly-4-vinylpyrrolidone in the presence of which the value of the rate constant increased by 30–70%. The strongest effect of the polymers is observed at 20–23 °C for dimegin, triglucamine salt of chlorine e6, and for tertrasodium salt of tetrasulfophenilporfirina at 30 °C. We suggest that the effect of the polymer on the effective rate constant relates to the restructuring of the supramolecular structure of polymers during temperature changes.

Thermal properties of poly(urethane-ester-siloxane)s based on hyperbranched polyester

Novel polyurethanes (PUs) were synthesized using hydroxy-terminated hyperbranched polyester (BH-20) and 4,4′-methylenediphenyl diisocyanate (MDI) as hard segments and hydroxy-terminated ethylene oxide-poly(dimethylsiloxane)-ethylene oxide triblock copolymer (PDMS-EO) as soft segment, with soft segment content ranging from 30 to 60 wt %. The PUs were synthesized by two-step solution polymerization method. The influence of the soft segment content on the structure, swelling behavior and thermal properties of PUs was investigated. According to the results obtained by swelling measurements, the increase of the hard segment content resulted in the increase of the crosslinking density of synthesized samples. DSC results showed that the glass transition temperatures increase from 36 to 65°C with increasing hard segment content. It was demonstrated using thermogravimetric analysis (TGA) that thermal stability of investigated PUs increases with increase of the soft PDMS-EO content. This was concluded from the temperatures corresponding to the 10 wt % loss, which represents the beginning of thermal degradation of samples.

Effects of temperature and concentration on the structure of ethylene oxide–propylene oxide–ethylene oxide triblock copolymer (Pluronic P65) in aqueous solution: a molecular dynamics simulation study

The effects of temperature and solution concentration on the structure of triblock polymeric surfactant (ethylene oxide)19(propylene oxide)29(ethylene oxide)19 (Pluronic P65) have been investigated by fully atomistic molecular dynamics simulations. The Flory–Huggins interaction parameter χ, hydrogen bonding and molecular mobility in the aqueous solution of P65 were investigated covering a composition range of 0.1–0.73 (water weight fraction) and a temperature range of 273–373 K. The Flory–Huggins parameters indicated that propylene oxide (PO) segments became hydrophobic with the increase in temperature, whereas ethylene oxide (EO) segments remained hydrophilic, which caused the increase in repulsion between EO and PO segments. The intermolecular hydrogen bonds in P65 solution including water–water hydrogen bonds and water–P65 hydrogen bonds increased with the increase in solution concentration and decreased with the increase in temperature. The critical micellar temperature of Pluronic P65 predicted by Flory–Huggins interaction parameter χ and hydrogen bonding was in good agreement with experimental data.

Adsorption of PEO–PPO–PEO Triblock Copolymers with End-Capped Cationic Chains of Poly(2-dimethylaminoethyl methacrylate)

We study the adsorption of a symmetric triblock copolymer of ethylene oxide, EO, and propylene oxide, PO, end-capped with quarternized poly(2-dimethylaminoethyl methacrylate), DMAEMA (DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24)). Light scattering and tensiometry are used to measure the relative size of the associated structures and surface excess at the air-liquid interface. The adsorbed amount, the amount of coupled water, and the viscoelasticity of the adsorbed polymer layer are measured on hydrophobic and hydrophilic surfaces (polypropylene, cellulose, and silica) by using quartz crystal microgravimetry (QCM) and surface plasmon resonance (SPR) at different ionic strengths and temperatures. The results of the experiments are compared with those obtained after adsorption of the uncharged precursor copolymer, without the cationic end-caps (EO(132)PO(50)EO(132)). DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) possesses higher affinity with the negatively charged silica and cellulose surfaces while the uncharged copolymer adsorbs to a larger extent on polypropylene surfaces. In this latter case, adsorption increases with increasing solution ionic strength and temperature. Adsorption of EO(132)PO(50)EO(132) on silica surfaces has little effect on the water contact angle (WCA), while adsorption of DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) increases the WCA of silica to 32°, indicating a large density of exposed PPO blocks upon adsorption. After adsorption of EO(132)PO(50)EO(132) and DMAEMA(24)-EO(132)PO(50)EO(132)-DMAEMA(24) on PP, the WCA is reduced by ≈14° and ≈28°, respectively, due to the exposed hydrophilic EO and highly water-soluble DMAEMA segments on the surfaces. The extent of surface coverage at saturation at the polypropylene/liquid interfaces (≈31 and 40 nm(2)/molecule obtained by QCM and SPR, respectively) is much lower, as expected, when compared with results obtained at the air/liquid interface, where a tighter packing is observed. The percentage of water coupled to the adsorbed cationic polymer decreases with solution ionic strength. Overall, these observations are ascribed to the effects of electrostatic screening, polymer hydrodynamic size, and solvency.

Micellisation of triblock copolymers of ethylene oxide and 1,2-butylene oxide: Effect of B-block length

We have used pyrene fluorescence spectroscopy and isothermal titration calorimetry (ITC) to investigate the effect of hydrophobic-block length on values of the critical micelle concentration (cmc) for aqueous solutions of triblock poly(butylene oxide)–poly(ethylene oxide)–poly(butylene oxide) block copolymers (BnEmBn, where m and n denote the respective block lengths) with hydrophobic block lengths in the range n=12–21. Combined with results from previous work on BnEmBn copolymers with shorter B blocks, plots of log10(cmc) (cmc in molar units and reduced to a common E-block length) against total number of B units (nt=n for diblock or nt=2n for triblock copolymers) display transitions in the slopes of the two plots, which indicate changes in the micellisation equilibrium. These occur at values of ntwhich can be assigned to the onset and completion of collapse of the hydrophobic B blocks, an effect not previously observed for reverse triblock copolymers. The results are compared with related data for diblock EmBn copolymers.

Solution microstructures of the micellar phase of Pluronic L64/SDS/water system

Here we report on a study dealing with a self-assembling ethylene oxide–propylene oxide–ethylene oxide triblock copolymer (Pluronic L64) and an anionic surfactant, sodium dodecyl sulfate (SDS), that in water at 25 °C form an interesting micellar region (L-phase). We have investigated the sequence of micelle structures in this L-phase across a wide interval of copolymer concentrations using phase diagram determination, steady shear, and NMR self-diffusion (pulsed gradient spin–echo, PGSE) experiments. In solutions which have been prepared at moderately low copolymer concentrations (ca. 20 wt.% L64) we report on a transition from discrete micelles to bicontinuous aggregates on the addition of SDS. This change was mainly inferred from self-diffusion coefficient patterns (i.e., the variation of copolymers and surfactant diffusivity vs. SDS content). At midrange and at higher polymer concentrations (i.e., in the interval from 50 to 80 wt.% L64) the L-phase occurred with a bicontinuous structure which was not modified by the progressive addition of SDS. Such a bicontinuous structure was identified by the comparison of self-diffusion coefficients of both cosolutes and the bulk viscosity (i.e., the behavior of zero-shear viscosity vs. SDS).

Rheology of worm-like micelles composed of tri-block copolymer in the limit of slow dynamics

We study the influence of micellar kinetics on the rheological behavior of worm-like micelles composed of tri-block copolymers of ethylene oxide and propylene oxide (EO20PO70EO20) in an aqueous solution containing KCl and ethanol. The kinetics of the micelles are adjusted by changing the ethanol concentration, according to a previous study in which the lifetime of the micelles was shown to decrease exponentially with increasing ethanol concentration. At higher ethanol concentrations (15 vol % EtOH), the worm-like micelles behave like Maxwell fluids at low frequencies, but have an upturn at higher frequencies, probably due to Rouse or breathing relaxation modes. At low ethanol concentrations (5 and 8 vol % EtOH) where the lifetime of the micelles is long, the rheological behavior is clearly non-Maxwellian, revealing a spectrum of relaxation times. The slow, block copolymer dependent growth of the micelles leads to scaling of viscosity with surfactant concentration, which varies with time. In this slow breaking regime, stirring of the solutions causes an increase of the viscosity, which slowly decreases once stirring is stopped. This apparent increase of the viscosity may be induced by the linking of ring-like micelles or by the formation of clusters of worm-like micelles (non-equilibrium structures), which disassemble when stirring is stopped.

Full separation of oligomers in block copolymers of ethylene oxide and propylene oxide

In this study di- and triblock copolymers of ethylene oxide (EO) and propylene oxide (PO) are analyzed by using CAP for one block and adsorption for the other block. This gives a complete picture of EO- and PO-based block copolymer with respect to the oligomers of both blocks. A full resolution of the individual oligomers can be achieved for both blocks up to an average molecular weight of 1000-1500 of each block.

Lipophilic Diol Induced Micellization of Pluronic® F88 in Water

The presence of a lipophilic S104 (also known as C14diol) induces micellization in a highly hydrophilic ethylene oxide–propylene oxide–ethylene oxide triblock copolymer Pluronic® F88 [(EO)103(PO)39–(EO)103] in water. The dynamic light scattering (DLS) and small angle neutron scattering (SANS) reveal that F88 remains as molecularly dissolved at ambient temperature even at fairly high concentrations (5 wt% or more). However, the micellization is induced at lower concentration/temperature in the presence of S104. The scattering measurements indicated micellar growth, though no phase transition was observed. The addition of hydrophobic S104 increases the aggregation numbers of the micellar system, but does not show a considerable increase in hydrodynamic size. The micellar parameters for the copolymer in the presence of S104 are reported at 30 and 40°C. Hydrophobic S104 interacts with PPO blocks of F88, makes the decreasing CMT of F88, which may be the synergistic effect. Using intermolecular rotating-frame nuclear overhauser effect (ROE) profiles, the interactions between PPO methyl and S104 terminal methyl groups can be obviously observed.

Kinetics and Mechanism of the Sphere-to-Rod Transition of Triblock Copolymer Micelles in Aqueous Solutions

The kinetics of the sphere-to-rod transition of micelles composed of triblock copolymers of ethylene oxide and propylene oxide (EO(20)PO(70)EO(20)) have been investigated using dynamic light scattering (DLS) and cryogenic electron transmission microscopy (Cryo-EM). Sphere-to-rod transition is induced by a solvent jump, initiated by adding KCl and ethanol to an aqueous micellar solution. The growth process of the wormlike micelles depends on the experimental conditions and has two distinct regions that can be described as initiation period and actual growth to equilibrium. All growth curves exhibit a single relaxation time that represents the lifetime of the micelles. The growth curves collapse into a master curve, when shifted by the relaxation time, indicating that the actual growth process of the micelles in all samples occurs through the same mechanism. The relaxation time decreases with increasing surfactant concentration. Additionally, some of the formed micelles exhibit a caterpillarlike shape in which some of the original spherical species can still be detected. These facts suggest that the micelles grow longer predominantly by random coagulation/fragmentation reactions involving micellar species of different sizes. However, the appearance of a unimer peak is detected with DLS during the growth stage. This implies that unimer exchange may also contribute to the elongation of the micelles.

ATR FTIR investigation of interactions and temperature transitions of poly(ethylene oxide), poly(propylene oxide) and ethylene oxide–propylene oxide–ethylene oxide tri-block copolymers in water media

ATR FTIR spectroscopy and quantum chemical calculations were used to investigate temperature dependent changes of structure and polymer–water interactions in a comparative study of poly(ethylene oxide), poly(propylene oxide) and a series of ethylene oxide–propylene oxide–ethylene oxide tri-block copolymers (Poloxamers, Pluronics) with different lengths of the blocks in aqueous media. The observed wavenumber shifts and intensity changes of the bands of different chemical groups of polymers and of water molecules served as a basis for the determination of structural changes and interactions of polymer chains with the surrounding water molecules. It was found that both hydrophilic (ether group–water) and hydrophobic (methyl group–water) interactions are significant for the temperature dependent phase behaviour. A model for the structural changes during the temperature transitions was specified.

The effect of the nonionic block copolymer pluronic P85 on gene expression in mouse muscle and antigen-presenting cells

DNA vaccines can be greatly improved by polymer agents that simultaneously increase transgene expression and activate immunity. We describe here Pluronic P85 (P85), a triblock copolymer of ethylene oxide (EO) and propylene oxide (PO) EO 26–PO 40–EO 26. Using a mouse model we demonstrate that co-administration of a bacterial plasmid DNA with P85 in a skeletal muscle greatly increases gene expression in the injection site and distant organs, especially the draining lymph nodes and spleen. The reporter expression colocalizes with the specific markers of myocytes and keratinocytes in the muscle, as well as dendritic cells (DCs) and macrophages in the muscle, lymph nodes and spleen. Furthermore, DNA/P85 and P85 alone increase the systemic expansion of CD11c + (DC), and local expansion of CD11c +, CD14 + (macrophages) and CD49b + (natural killer) cell populations. DNA/P85 (but not P85) also increases maturation of local DC (CD11c + CD86 +, CD11c + CD80 +, and CD11c + CD40 +). We suggest that DNA/P85 promotes the activation and recruitment of the antigen-presenting cells, which further incorporate, express and carry the transgene to the immune system organs.

Influence of a hydrophobic diol on the micellar transitions of Pluronic P85 in aqueous solution

Micellization behavior of an amphiphilic ethylene oxide–propylene oxide–ethylene oxide tri-block copolymer Pluronic P85 [(EO) 26(PO) 39–(EO) 26] in aqueous solution and in the presence of a hydrophobic C 14diol (also known as Surfynol ®104) was examined by physico-chemical methods such as viscometry, cloud point (CP) and scattering techniques viz. dynamic light scattering (DLS) and small angle neutron scattering (SANS). The addition of diol decreases the cloud point and gelation temperature of aqueous Pluronic P85 copolymer solution. DLS and SANS measurements of the polymer in aqueous solution indicated micellar growth and sphere to rod transition in the presence of diol. Surfynol ®104 is a sparingly water soluble diol surfactant with a solubility of ∼0.1 wt%. However, up on addition to Pluronic solution, diol gets incorporated in the block copolymer micelles and leads to structural transition of the micelles. An increase in the temperature and the presence of added sodium chloride in the solution further enhances this effect. The addition of hydrophobic C 14diol increases the hydrodynamic size and aggregation numbers of the micellar system. The micellar parameters for the copolymer in the presence of C 14diol are reported at different temperatures and added sodium chloride concentrations.

Effects of Salts and Ethanol on the Population and Morphology of Triblock Copolymer Micelles in Solution

The morphological changes of micelles composed of triblock copolymer of ethylene oxide and propylene oxide (EO20PO70EO20) in the presence of different inorganic salts and ethanol have been investigated using dynamic light scattering (DLS), rheometry, and cryogenic transmission electron microscopy (cryo-EM). The following salts were studied: KF, KCl, KI, LiCl, and CsCl. In the presence of KF, KCl, and CsCl, spherical and wormlike micelles coexist. LiCl and KI have little influence on the morphology of the micelles, whereas KF has the most pronounced effect. In agreement with the well-known Hoffmeister anion salt series, F- has the strongest effect of the three anions studied (F-, Cl-, I-). In contrast, the effectiveness of the cation type does not follow the original Hoffmeister cation series. The addition of ethanol to the KCl micellar solutions leads to the formation of more or longer wormlike micelles, which start to interact at certain copolymer concentrations depending on the volume fraction of ethanol added. Both the dilute and the semidilute regimes of the wormlike micelles were studied. The length of the micelles reaches a maximum value at around 8-10 vol % ethanol, after which it decreases again. At higher ethanol concentrations (18 vol %), spherical micelles are formed. Conclusions from this study enhance our understanding of the role played by ethanol and salts in the formation of micelle-templated mesoporous materials, such as SBA-15.