EO-PO Copolymer Research Articles

Temperature-Transferable Coarse-Grained Model for Poly(propylene oxide) to Study Thermo-Responsive Behavior of Triblock Copolymers.

Thermo-responsive behavior of ethylene oxide (EO)-propylene oxide (PO) copolymers makes them suitable for many potential applications. Reproducing the origins of the tunable properties of EO-PO copolymers using coarse-grained (CG) models such as the MARTINI force field is critically important for building a better understanding of their behavior. In the present work, we have investigated the effects of coarse-graining on the water-polymer interaction across a temperature range. We compared the performance of different all-atom force fields to find the most appropriate one for the purpose of PO block parameterization in the MARTINI platform. We parameterized a CG temperature-dependent PO model based on the reproduction of the atomistic free energy of transfer of propylene oxide trimer from octane to water over a range of temperatures (20-60 °C) and compared the atomistic bond and angle distributions. Then, we used the model to study the effects of EO/PO ratio, molecular weight, and concentration on the thermo-responsive behavior of EO-PO copolymers in water. The results show an excellent agreement with experiments in different areas. Our temperature-dependent model reproduces (1) micellar phase above critical micelle temperature (CMT) and unimer phase below CMT for different Pluronics (a class of EO-PO triblock copolymers) spanning many EO/PO ratios and molecular weights; (2) spherical-to-rodlike micellar shape transition for Pluronics with 60 wt % of PO content or more; (3) diffusion coefficients for Pluronics with high PO content (P104 Pluronic with a PO mass of 3500 g mol-1) across a broad range of temperatures; and (4) micelle core size and micelle diameter similar to experimental results. Overall, our model improves the temperature sensitivity of EO-PO copolymers of existing models significantly, particularly for copolymers that are dominated by PO agents.

Molecular Destabilization Mechanism of Asphaltene Model Compound C5Pe Interfacial Film by EO-PO Copolymer: Experiments and MD Simulation

It is commonly believed that asphaltenes are the main components that contribute to the formation of the rigid film which stabilizes W/O emulsions in petroleum industry. In order to investigate the...

Separation of Antioxidant Peptides from Pepsin Hydrolysate of Whey Protein Isolate by ATPS of EOPO Co-polymer (UCON)/Phosphate

An aqueous two-phase system (ATPS) consisting of poly(ethylene glycol-ran-propylene glycol) monobutyl ether (UCON)/phosphate was developed for the separation of the antioxidant peptides from pepsin hydrolysate of Whey Protein Isolate (WPI). The efficiency of the separation was evaluated based on the DPPH radical scavenging activity, ABTS radical scavenging activity and ferric reducing antioxidant power (FRAP) of the separated peptides. The effects of some parameters on the partition of antioxidant peptides were investigated. An efficient separation of antioxidant peptides was achieved using ATPS with pH of 4.0, 4 mL of UCON solution (40%, w/w), 4 mL of KH2PO4 solution (15.5%, w/w), 2 mL of WPI hydrolysate and 0.40 g/10 mL of NaCl. Reversed-phase high-performance liquid chromatography (RP-HPLC), amino acid analyzer and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used to characterize the purified peptides separated by the ATPS. The peptides in top phase were less polar than those in bottom phase. More antioxidative and hydrophobic amino acids were extracted to the top phase of ATPS, and the peptides with the amino acid sequences with antioxidant activities moved to the top phase as well. In conclusion, antioxidant peptides were successfully separated from the WPI hydrolysate by UCON/phosphate ATPS.

Aqueous two-phase systems with thermo-sensitive EOPO co-polymer (UCON) and sulfate salts: Effect of temperature and cation

Poly(ethylene glycol-ran-propylene glycol) lies within a family of thermo-separating polymers (commercialized as “UCON”), thus they can be easily recovered from aqueous solution just heating above its lower critical solution temperature. Phase diagrams for UCON – sulfate salt aqueous two-phase systems (ATPS) have been obtained experimentally in the temperature range 273.15–308.15K by analysis of the equilibrium phases. The binodal curves and tie-lines have been correlated using suitable methods from the literature. The effect of temperature and the cation used in the sulfate salt (sodium, potassium, ammonium) are discussed. Temperature increases the heterogeneous region size while increases the polymer concentration in the polymer-rich phase and reduces the salt concentration in the salt-rich phase. This effect produces the phase inversion at high temperatures. The cation ability for phase splitting in these ATPS increases with the (more negative) Gibbs energy of hydration of the cation: Na+>K+>NH4+.

Collaborative Interactions between EO-PO Copolymers upon Mixing

Chemical demulsification is the most extensively used method for breaking water-in-diluted bitumen emulsions in oil sands processing. In this paper, the properties and performance of three demulsifier formulations and their individual EO-PO polymer components were studied. The EO-PO polymers and demulsifier formulations were characterized by their relative solubility number (RSN). The results showed that the RSN is an additive property. The dehydration efficiency of the demulsifier formulation was higher than the individual components at the same dosage, signifying that there were collaborative interactions among the polymers on mixing. Correlations between performance of the demulsifiers and interfacial tension (IFT), yield stress of underflow, and bitumen loss to tailings were investigated. The results showed no correlation between the performance of the demulsifiers and equilibrium IFT. Correlations were observed between dehydration efficiency and both yield stress of the underflow and bitumen loss to ...

Phase System Selectivity and Peak Capacity in Liquid Column Chromatography ? the Impact on Two-Dimensional Separations

Correlations between the separation selectivity in aqueous and non-aqueous reversed-phase systems and in normal-phase systems were investigated. The degree of correlation between the selectivity in separation systems can be useful indicator of suitability of phase systems for two-dimensional HPLC separations. The real gain in peak capacity improves as the orthogonality of separation systems increases and impairs as the correlation between the selectivity of coupled systems increases. Similarity between the systems was determined on the basis of the change in retention (selectivity) attributed to suitable structural descriptors, such as polar interaction indices, number of carbon atoms in the lipophilic parts of the molecules or on number of repeat monomer units in high-molecular compounds. Based on this approach, the degree of orthogonality of the HPLC separation systems was evaluated and correlated with the peak capacity in two-dimensional HPLC. The approach was tested with simple aromatic compounds and was used to characterise retention behaviour of the individual species in samples of synthetic EO-PO co-polymers.

Tryptophan-tagged cutinase studied by steady state fluorescence for understanding of tag interactions in aqueous two-phase systems

Genetic engineering has been used to construct fusion proteins of Fusarium solani pisi cutinase and tryptophan-based tags, expressed in Saccharomyces cerevisiae, to increase the partitioning in aqueous two-phase systems. The separation systems were composed of thermoseparating polymers (random copolymers of ethylene oxide and propylene oxide, EOPO) and detergents (C 12EO n ). In this study, the fluorescence behaviour of the peptide-tagged protein, free peptide tag and tryptophan was investigated. The tryptophan-tagged proteins, cutinase-(WP) 4 and cutinase-TGGSGG-(WP) 4, showed emission spectra similar to the free peptides and tryptophan, indicating solvent exposure of the tag. The influence of polymers and detergents on the fluorescence of tagged proteins was examined. When peptides and tagged proteins were exposed to polymer, a slight blue shift of the emission maximum was observed. Larger blue shifts of the emission maximum were observed when C 12EO n detergents were utilised. The results correlate with aqueous two-phase partitioning where addition of C 12EO n detergents results in more extreme partitioning compared to systems containing only polymers. Dynamic light scattering (DLS) measurements of the EOPO copolymers were carried out, showing that the polymers did not aggregate at concentrations used in aqueous two-phase systems. Quenching of fluorescence with iodide for both proteins and peptide tags was studied. Plots according to the Stern–Volmer equation resulted in a linear fit, indicating exposed tryptophan residues for both free peptides and fusion proteins. The quenching constants were similar for both tagged protein and free peptide tag. The fluorescence results indicated that the tryptophan residues in the tag were exposed to the solvent and could interact with detergents and polymers in the two-phase systems.

Biomolecule Separation Using Temperature-Induced Phase Separation with Recycling of Phase-Forming Polymers

We review our recent work on the thermoseparating polymers in aqueous two-phase extractions of biomolecules. Random copolymers of ethylene oxide and propylene oxide (EOPO copolymers) are thermoseparating in water solution, i.e., at temperatures above the cloud point a concentrated copolymer phase and a water phase almost free of copolymer are formed. This phase behavior makes it possible to recycle copolymers after biomolecule extraction. A system for protein purification has been developed based on an EOPO copolymer/hydroxypropyl starch aqueous two-phase system. The target protein is extracted into the EOPO phase. Nonionic surfactants have been added to improve the partitioning to the copolymer phase. The EOPO phase is removed after extraction, and the temperature is increased above the cloud point. The target protein is recovered in the water phase, and the copolymer and surfactant is obtained as a concentrated phase free from protein. Copolymer and surfactant can be recovered after thermoseparation to 85−90% and four recycle steps have been accomplished. Covalent binding of an affinity ligand to the EOPO copolymer can improve the partitioning of a target protein to the EOPO phase. The EOPO ligand can be recycled after thermal separation. A novel one-polymer aqueous two-phase system containing only thermoseparating EOPO copolymer and water has been developed for smaller biomolecules, e.g., peptides. Above the copolymer's cloud point, hydrophobic peptides will partition to the EOPO-enriched phase and hydrophilic peptides to the water phase. Proteins can be extracted in a one-polymer phase system containing a hydrophobically modified EOPO copolymer (HM-EOPO). The target protein is partitioned to the HM-EOPO phase. The copolymer can be recycled after back-extraction of the protein to a new water phase.

Polymer recycling in aqueous two-phase extractions using thermoseparating ethylene oxide–propylene oxide copolymers

This is a study on the recovery and recycling of copolymer in aqueous two-phase systems containing random copolymers of ethylene oxide (EO) and propylene oxide (PO). The random copolymers separate from water solution when heated above the lower critical solution temperature (LCST). The primary phase systems were composed of EOPO copolymer and hydroxypropyl or hydroxyethyl starch. After phase separation the upper EOPO phase was removed and subjected to temperature induced phase separation. Copolymers with different EO/PO compositions have been investigated, EO50PO50 [50% EO and 50% PO (w/w)], EO30PO70 and EO20PO80. The temperature required for thermoseparation decreases when the PO content of the copolymer is increased. The effect on the recovery of copolymer after addition of salts, a second polymer or protein was investigated. The added components increased the recovery of copolymer after thermoseparation, e.g., increased the amount copolymer separated from the water phase after thermoseparation. Recycling of copolymer and measurements of polymer concentrations in the primary top and bottom phases after repeated recycling steps was performed. The fluctuation in polymer concentration of the phases was very small after recycling up to four times. Partitioning of the proteins BSA and lysozyme was studied in primary phase systems after recycling of copolymer. The partition coefficients of total protein and lysozyme was not significantly changed during recycling of copolymer. More than 90% of the copolymer could be recovered in the thermoseparation step by optimising the temperature and time for thermoseparation. In repeated phase partitionings in EOPO–starch systems the EO50PO50 copolymer could be recovered to 77% including losses in primary system and thermoseparation, which is equivalent to a total copolymer reuse of 4.3 times.

Genetic engineering of protein-peptide fusions for control of protein partitioning in thermoseparating aqueous two-phase systems

Genetic engineering has been used for the fusion of peptides, with different length and composition, on a protein to study the effect on partitioning in aqueous two-phase systems containing thermoseparating polymers. Peptides containing 2-6 tryptophan residues or tryptophan plus 1-3 lysine or aspartate residues, were fused near the C-terminus of the recombinant protein ZZT0, where Z is a synthetic IgG-binding domain derived from domain B in staphylococcal protein A. The partitioning behavior of the peptides and fusion proteins were studied in an aqueous two-phase system composed of dextran and the thermoseparating ethylene oxide-propylene oxide random copolymer, EO30PO70. The zwitterionic compound beta-alanine was used to reduce the charge-dependent salt effects on partitioning, and to evaluate the contribution to the partition coefficient from the amino acid residues, Trp, Lys, and Asp, respectively. Trp was found to direct the fusion proteins to the EO-PO copolymer phase, while Asp and Lys directed them to the dextran phase. The effect of sodium perchlorate and triethylammonium phosphate on the partitioning of the fusion proteins was also studied. Salt effects were directly proportional to the net charge of the fusion proteins. Sodium perchlorate was found to be 3.5 times more effective in directing positively charged proteins to the EO-PO copolymer phase compared to the effect of triethyl ammonium phosphate on negatively charged proteins. An empirical correlation has been tested where the fusion protein partitioning is a result of independent contributions from unmodified protein, fused peptide, and salt effects. A good agreement with experimental data was obtained which indicates the possibility, by independent measurements of partitioning of target protein and fusion peptide, to approximately predict the fusion protein partitioning.

Genetic engineering of protein–peptide fusions for control of protein partitioning in thermoseparating aqueous two‐phase systems

Genetic engineering has been used for the fusion of peptides, with different length and composition, on a protein to study the effect on partitioning in aqueous two-phase systems containing thermoseparating polymers. Peptides containing 2–6 tryptophan residues or tryptophan plus 1–3 lysine or aspartate residues, were fused near the C-terminus of the recombinant protein ZZT0, where Z is a synthetic IgG-binding domain derived from domain B in staphylococcal protein A. The partitioning behavior of the peptides and fusion proteins were studied in an aqueous two-phase system composed of dextran and the thermoseparating ethylene oxide–propylene oxide random copolymer, EO30PO70. The zwitterionic compound β-alanine was used to reduce the charge-dependent salt effects on partitioning, and to evaluate the contribution to the partition coefficient from the amino acid residues, Trp, Lys, and Asp, respectively. Trp was found to direct the fusion proteins to the EO–PO copolymer phase, while Asp and Lys directed them to the dextran phase. The effect of sodium perchlorate and triethylammonium phosphate on the partitioning of the fusion proteins was also studied. Salt effects were directly proportional to the net charge of the fusion proteins. Sodium perchlorate was found to be 3.5 times more effective in directing positively charged proteins to the EO–PO copolymer phase compared to the effect of triethyl ammonium phosphate on negatively charged proteins. An empirical correlation has been tested where the fusion protein partitioning is a result of independent contributions from unmodified protein, fused peptide, and salt effects. A good agreement with experimental data was obtained which indicates the possibility, by independent measurements of partitioning of target protein and fusion peptide, to approximately predict the fusion protein partitioning. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 135–144, 1999.

Partitioning of Amino Acids by Aqueous Two-Phase Systems Combined with Temperature-Induced Phase Formation

A copolymer of 50% ethylene oxide and 50% propylene oxide (EOPO(1:1) ) has been used in aqueous two-phase partitioning of amino acids. This EOPO(1:1) copolymer has a cloud point of 70 °C, at which it separates from water. The cloud point can be lowered to 45 °C by the addition of 0.2 M sodium sulfate. Amino acids are first partitioned at 25 °C in a system composed of EOPO(1:1) and hydroxypropyl starch (PES) . EOPO(1:1) is enriched in the top phase and PES is in the bottom phase. Then, the top phase can be removed and its temperature increases above the cloud point of the EOPO(1:1) . This results in formation of a new two-phase system with a top aqueous phase containing most of the amino acids and a bottom EOPO(1:1) -rich phase, thus allowing the lower EOPO(1:1) -rich phase to be removed and recycled for a second extraction. Amino acids are recovered exclusively in top aqueous phase.

Effects of salts and the surface hydrophobicity of proteins on partitioning in aqueous two-phase systems containing thermoseparating ethylene oxide-propylene oxide copolymers

The partitioning of five well-characterized model proteins, bovine serum albumin (BSA), lysozyme, β-lactoglobulin A, myoglobulin and cytochrome c, in aqueous two-phase systems has been studied. As top phase polymers PEG (polyethylene glycol, 100% EO) and the thermoseparating ethylene oxide (EO)-propylene oxide (PO) random copolymers,Ucon 50-HB-5100 (50% EO, 50% PO) and EO 30PO 70 (30% EO, 70% PO), respectively, were used. The top phase polymers are increasing hydrophobicity with increasing content of PO. Reppl PES 200 (hydroxypropyl starch) was used as the bottom phase polymer. Phase diagraams for Reppal PES 200-PEG and Reppal PES 200-EO 30PO 70 two-phase systems were determined. The partitioning of four salts with different hydrophobicity, and also the effect of the salts on protein partitioning inn these systems, was studied. It waas found that the partitioning of the salts followed the Hofmeister series. The partitioning of proteins with low surface hydrophobicity, mygglobin and cytochrome c, was little affected by hydrophobic polymers and salts. However, the parttioning of a protein with higher surface by hydrophobiocity, lysozyme, was strongly affected when polymer hydrophobicity was increased and a hydrophobicity counterion was used. A protein with relatively hydrophobic surfac can be partitioned to a phase containing a thermoseparating EO-PO copolymer by using a hydrophobic counterion. The parttioning of lysozyme and cytochrome c in the polymer-water system formed after temperature-induced phase separation was also examined. Both proteins partitioned exclusivvely to the water phase. A separation of the protein and polymer was obtained by temperature-induced phase separation on the isolated phase containing the EO-PO copolymer. The partitioning data also indicatedthat the hydroxypropyl starch polymer had a weak negative charge.

フローテーション法脱墨剤の開発 脱墨機構に関する考察

Following the recent worldwide demand for high-quality recycled pulp, the technology for deinking equipment and deinking agents has made remarkable progress.Particularly, there is a great demand for new, efficient deinking agents designed for state of the art equipment coming into use by various paper manufacturers.In response to this demand, a laboratory evaluation method was developed to measure deinking agent efficiency. By introducing the concepts of ink removal energy in the pulping process, agitation Reynolds number and gas-liquid ratio in the flotation process, a method capable of providing experimental conditions suitable to represent actual mill systems was achieved. Using this evaluation method, new deinking agents were developed having excellent ink removal and ink collection efficiency and rapid foam collapse after flotation. By utilizing the developed evaluation method and controlling the addition of alkyleneoxide to a high alcohol, the above-mentioned properties can be fitted to individual mill systems. Newly developed high-alcohol-type EOPO copolymers (single-chain type) are compared to fatty acid and oil & fat type EOPO copolymers (double-chain type) using the described laboratory method.

Li ion conductive polymer electrolyte based on polyglycerine

New polymers were prepared by grafting EO homopolymer or EO-PO copolymer to polyglycerine having ether oxygens in addition to those of PEO. The temperature dependences of ionic conductivities were investigated for crosslinked films of these polymers containing lithium perchlorate. These depended on the degree of the polymerization of EO and the copolymerization ratio of PO to EO. The best sample of this work showed the conductivity of 1.1×10 −4 S cm −1 at 30°C. It is suggested by the experimental results that the sudden change of ionic conductivity relates to the latent heat at the melting point.