Increase Of PEG Molecular Weight Research Articles

Fabrication of ultrafiltration membranes by poly (aryl ether nitrile) with poly (ethylene glycol) as additives.

A new kind of flat sheet ultrafiltration membrane was prepared by a promising membrane material, poly (aryl ether nitrile) (PEN), via non-solvent induced phase separation. The effect of solvents, N-methyl-2-pyrrolidone (NMP) and dimethyl acetamide (DMAc), as well as additive of poly (ethylene glycol) (PEG) with different molecular weights on the structure and permeation performance of synthesized membranes were investigated. Comparing with NMP, DMAc is more suitable for the casting solution preparation due to better solubility. A gradually changing pore from sponge-like to finger-like can be observed when PEG was added with DMAc as solvent, while a finger-like pore structure always appears in the NMP system with or without PEG. In both systems, the formation of macrovoids is effectively promoted by the addition of PEG, and higher porosity membranes can be obtained by PEG with higher molecular weight. With the increase of PEG molecular weight from 400 to 10,000 Da, the permeate flux increases from 74.5 to 114.3 L·m-2·h-1 and from 102.0 to 130.8 L·m-2·h-1 under a 100 kPa pressure-driven when NMP and DMAc were used as solvents, respectively. The membranes prepared by DMAc exhibit outstanding rejection of BSA with rejections all above 96.5%.

Unraveling the Effect of PEG Chain Length on the Physical Properties and Toxicant Removal Capacities of Cross-Linked Network Synthesized by Thiol-Norbornene Photoclick Chemistry.

With the aim to develop chemical adsorbents that are inherently nontoxic to living beings and the environment, a gel system based on thiol–norbornene photoclick chemistry was developed. Norbornene was strategically functionalized with different poly(ethylene glycol) (PEG) chains to produce PEG-functionalized macromonomers. The influence of incorporating PEG in the cross-linked network was evaluated on the basis of its physical properties and dye-removing efficiency from aqueous solutions. The excellent swelling ability of the gels in organic solvents was found to improve with the PEG chain length. The rheological measurements of the as-synthesized materials also exhibited the presence of elasticity in the network, and a decrease in storage and loss moduli was observed with an increase in PEG molecular weight. The materials possess excellent thermal stability, which enhanced with an increase in PEG chain length, as revealed from thermogravimetric analysis (TGA). Differential scanning calorimetry (DSC) studies revealed the tendency of higher-molecular-weight PEG to form a crystalline phase in the network. Kinetic studies of dye removal from aqueous solutions by the as-prepared cross-linked networks indicate that the dye removal proceeds via pseudo-second-order kinetics. The study of adsorption isotherm of the removal process indicates that the adsorption follows the Langmuir isotherm model. In this present work, we have thoroughly evaluated the influence of PEG chain length on several physical properties and toxic cationic dye removal efficiencies of thiol–norbornene photo-cross-linked networks.

Partitioning performance of molybdenum in poly (ethylene glycol) + sodium sulfate + water aqueous two-phase systems

Partition performance of molybdenum (VI) by aqueous two-phase systems (ATPSs) composed of poly (ethylene glycol) (PEG1000, PEG2000 and PEG4000)+sodium sulfate+H2O without any extractant was systematically studied. Response surface optimization method was applied to study the effects of different factors such as, the type and concentration of PEG, sodium sulfate concentration, molybdenum concentration and temperature on the phase volume ratio, partition coefficient and extraction rate of molybdenum. The experimental results showed that the phase volume ratio changes with all four parameters, resulting from hydration of sodium sulfate, dehydration of increasing temperature and replace of molybdenum to water. The partitioning coefficient and extraction rate of molybdenum increases as increasing sodium sulfate concentration being of hydration of sodium sulfate, and also increases with increasing temperature, indicating that the transfer process of molybdenum from the salt-rich phase to the PEG-rich phase is endothermic. With the increase of PEG molecular weight (PEG1000, PEG2000 and PEG4000), the phase volume ratio decreases and partitioning coefficient and extraction rate of molybdenum goes up. The extraction mechanism can be deduced that molybdenum was extracted into PEG-rich phase by electrostatic attraction between polymolybdate anion and protonated COC bond in PEG molecule due to relatively high hydrophobicity of polymolybdate anion under the salting-out effect of phase-forming sodium sulfate by the change of initial and equilibrium pH in aqueous phase, FTIR and Raman spectrum analysis. A better result on extracting and separating molybdenum was achieved by applying the proposed method to the leaching liquor of low-grade molybdenite concentrate.

Bleomycin-Loaded pH-Sensitive Polymer⁻Lipid-Incorporated Liposomes for Cancer Chemotherapy.

Cancer chemotherapeutic systems with high antitumor effects and less adverse effects are eagerly desired. Here, a pH-sensitive delivery system for bleomycin (BLM) was developed using egg yolk phosphatidylcholine liposomes modified with poly(ethylene glycol)-lipid (PEG-PE) for long circulation in the bloodstream and 2-carboxycyclohexane-1-carboxylated polyglycidol-having distearoyl phosphatidylethanolamine (CHexPG-PE) for pH sensitization. The PEG-PE/CHexPG-PE-introduced liposomes showed content release responding to pH decrease and were taken up by tumor cells at a rate 2.5 times higher than that of liposomes without CHexPG-PE. BLM-loaded PEG-PE/CHexPG-PE-introduced liposomes exhibited comparable cytotoxicity with that of the free drug. Intravenous administration of these liposomes suppressed tumor growth more effectively in tumor-bearing mice than did the free drug and liposomes without CHexPG-PE. However, at a high dosage of BLM, these liposomes showed severe toxicity to the spleen, liver, and lungs, indicating the trapping of liposomes by mononuclear phagocyte systems, probably because of recognition of the carboxylates on the liposomes. An increase in PEG molecular weight on the liposome surface significantly decreased toxicity to the liver and spleen, although toxicity to the lungs remained. Further improvements such as the optimization of PEG density and lipid composition and the introduction of targeting ligands to the liposomes are required to increase therapeutic effects and to reduce adverse effects.

Effect of poly(ethylene glycol) molecular weight on CO2/N2 separation performance of poly(amide-12-b-ethylene oxide)/poly(ethylene glycol) blend membranes

Membranes from block copolymer poly (amide-12-b-ethylene oxide) (Pebax1074) and its blends with different molecular weight poly (ethylene glycol) (PEG) (200, 400, 600, 1500, 4600 and 8000) were prepared. The thermal properties and structures of Pebax1074/PEG blend membranes were characterized by DSC and SEM, and the gas permeation properties of CO2 and N2 were also investigated at different temperatures. For Pebax1074/PEG blend membranes with low molecular weight PEG (MW≤ 600), higher gas permeabilities than Pebax1074 were achieved. The permeability increased with the increase of PEG molecular weight. The addition of low molecular weight PEG resulted in decrease in activation energy of permeation. For Pebax1074/PEG blend membranes with high molecular weight PEG (MW≥ 1500), due to the melt of PEO phase crystals, the gas permeation properties of blend membranes were temperature-dependent, which could be divided into crystalline region, transition region and amorphous region according to two different transition temperatures. PEG molecular weight and operation temperature determined different gas permeation properties of Pebax1074/PEG blend membranes in three regions. The activation energies of permeation in crystalline region were larger than those in amorphous region.

Design of high efficiency PVDF-PEG hollow fibers for air filtration of ultrafine particles

This study reveals as the first attempt to apply hollow fibers for air filtration of ultrafine particles. Different from symmetric nano-fiber filters and non-woven fabrics, asymmetric polyvinylidene fluoride – polyethylene glycol (PVDF-PEG) hollow fibers with high gas permeances have been developed by the dry-jet wet-spinning process. The addition of high molecular weight PEGs in spinning dopes facilitates the formation of loosely connected cross-section and porous outer skin, thus enhances the gas permeance for air filtration. Under the inside-out testing mode, all PVDF-PEG hollow fibers display excellent filtration efficiency of 99.999% against polydispersed NaCl particles with a geometric mean size of ~30nm. Since permeance increases with an increase in PEG molecular weight in spinning dope, the PVDF-PEG hollow fiber with a PEG molecular weight (MW) of 12,000Da possesses the highest quality factor because it has the highest permeance and lowest transmembrane pressure. However, the PVDF-PEG hollow fiber with a PEG MW of 8000Da has the best mechanical properties. Under the dead-end filtration, the filtration efficiency increases with an increase in air flow rate. This trend is contrary to the findings observed in the flat and symmetric fibrous filtration. The asymmetric structure in the cross-section of the newly developed hollow fibers may enhance aerosol deposition via direct impaction and Brownian motion at high flow rates. The dead-end filtration results also show that the quality factor is higher at a lower flow rate. Similarly, the cross-flow filtration results show that the hollow fiber modules operated at low cross-flow ratios have high quality factors. Therefore, it is preferred to operate the newly developed PVDF-PEG hollow fiber at a low flow rate or low cross-flow ratio. This study may provide useful insights for developing hollow fibers for air filtration with the optimal operation conditions.

Influence of the concentration and molecular weight of polyethylene glycol on the structure and permeability of polysulfone hollow fiber membranes

The influence of the concentration and molecular weight of polyethylene glycol (PEG, 400–40000 g mol–1) on the phase state and viscosity of ternary polysulfone–polyethylene glycol–N,N-dimethylacetamide solutions has been studied. It was shown that an increase in PEG molecular weight (MW) results in a decrease in the region of existence of homogeneous solutions on the phase diagram due to polymer incompatibility, and in an increase in the viscosity of polymer solutions. At a constant PEG concentration (5%) the viscosity depends on PEG MW in a complicated way: in the range of PEG molecular weights 1000–6000 g mol–1 the viscosity is nearly unchanged, but when the PEG MW exceeds 6000 g mol–1 a sharp increase in the viscosity of the polymer solutions is observed. It was shown that changes in the membrane performance are determined by PEG concentration in the dope solution. At a PEG concentration of 5% an increase in PEG MW results in an increase in membrane performance and a decrease in the rejection capability; at an increase in PEG concentration in the dope solution up to 25% the maximum pure water flux was observed for PEG-400. The bubble point test showed that with an increase in PEG molecular weight a fraction of large pores, which can be considered as selective layer defects, increases.

Interfacial partitioning behaviour of bovine serum albumin in polymer-salt aqueous two-phase system

A relationship is proposed for the interfacial partitioning of protein in poly(ethylene glycol) (PEG)-phosphate aqueous two-phase system (ATPS). The relationship relates the natural logarithm of interfacial partition coefficient, ln G to the PEG concentration difference between the top and bottom phases, Δ[PEG], with the equation ln G=AΔ[PEG]+B. Results showed that this relationship provides good fits to the partition of bovine serum albumin (BSA) in ATPS which is comprised of phosphate and PEG of four different molecular weight 1450g/mol, 2000g/mol, 3350g/mol and 4000g/mol, with the tie-line length (TLL) in the range of 44-60% (w/w) at pH 7.0. The decrease of A values with the increase of PEG molecular weight indicates that the correlation between ln G and Δ[PEG] decreases with the increase in PEG molecular weight and the presence of protein-polymer hydrophobic interaction. When temperature was increased, a non-linear relationship of ln G inversely proportional to temperature was observed. The amount of proteins adsorbed at the interface increased proportionally with the amount of BSA loaded whereas the partition coefficient, K remained relatively constant. The relationship proposed could be applied to elucidate interfacial partitioning behaviour of other biomolecules in polymer-salt ATPS.

Liquid–liquid equilibrium of aqueous two-phase systems containing poly(ethylene glycol) of different molecular weights and several ammonium salts at 298.15 K

Liquid–liquid equilibrium data of aqueous two-phase systems (ATPSs) formed by poly(ethylene glycol) (PEG) of different molecular weights (1000, 2000, 6000)+ammonium carbonate ((NH4)2CO3), ammonium tartrate ((NH4)2C4H4O6), diammonium hydrogen phosphate ((NH4)2HPO4), ammonium sulfate ((NH4)2SO4)+water were determined at 298.15K, respectively. The binodal data were correlated by using a four-parameter equation. The effect of PEG molecular weight on binodal curves was investigated, and it was found that the biphasic region expanded with an increase in PEG molecular weight. Meanwhile, it was also observed that the ability of the investigated salts for phase separation follows the order: (NH4)2HPO4>(NH4)2SO4>(NH4)2C4H4O6>(NH4)2CO3. Furthermore, a relatively simply two parameter equation, Othmer–Tobias and Bancroft equations was successfully used to correlate the tie-line data.

Electrically enhanced solute permeation across poly(ethylene glycol)–crosslinked poly(methyl vinyl ether-co-maleic acid) hydrogels: Effect of hydrogel crosslink density and ionic conductivity

Swelling kinetics, ionic conductivity and electrically assisted solute permeation (theophylline, methylene blue and fluorescein sodium) of poly(ethylene glycol) (PEG) crosslinked poly(methyl vinyl ether-co-maleic acid) (PMVE/MA) hydrogels are presented. The effects of PMVE/MA concentration and PEG molecular weight (MW) on swelling behaviour and network parameters were investigated in phosphate buffered saline (pH 7.4). The percentage swelling of hydrogels increased, and the crosslink density decreased, with a decrease in PMVE/MA content and with an increase in PEG MW. The ionic conductivity of the formulation was found to increase with an increase in PEG MW. The application of an electrical current led to a significant enhancement in the rate and extent of solute permeation across the swollen hydrogels. Furthermore, it was found that the extent of solute permeation enhancement following current application was dependent upon the crosslink density and ionic conductivity of the formulation. In general, a decrease in crosslink density and an increase in ionic conductivity led to a greater enhancement in solute permeation following current application. The electro-responsive nature of these hydrogels suggests that have a potential application in electrically controlled drug delivery systems.

Phase Separation Behavior of Cocamidopropyl Betaine/Water/Polyethylene Glycol System

Phase separation behavior of cocamidopropyl betaine/water/polyethylene glycol (PEG) system was studied. The effects of concentration and molecular weight of PEG on the phase separation behavior were investigated. Clouding occurred when the concentration of PEG was large enough in the betaine aqueous solution, and the concentration of PEG at cloud point decreased with the increase of PEG molecular weight for a constant betaine concentration. The bottom phase was the PEG-rich phase, and the upper phase was the betaine-rich phase. The volumetric ratio of PEG-rich phase to betaine-rich phase, at the same difference between the PEG concentration and the one at the cloud point, Δ C cp (0.1 g·ml −1), decreased as the PEG molecular weight increased and approached 1 for higher PEG molecular weight (about 20000), which was similar to the typical aqueous two-phase system. This volumetric ratio depended on the initial PEG concentration, but independent of PEG molecular weight. The concentration ratio of betaine to PEG in both phases depended on the Δ C cp, independent of PEG molecular weight.

Study of Phase Behavior of Poly(ethylene glycol)–Polysorbate 80 and Poly(ethylene glycol)–Polysorbate 80–Water Mixtures

Mixtures of poly(ethylene glycols) (PEGs) with polysorbate 80 are often used to dissolve poorly water‐soluble drugs in dosage forms, where polysorbate 80 helps either in enhancing dispersion or in inhibiting precipitation of drugs once the solution is mixed with water. Binary phase diagrams of polysorbate 80 with several low molecular weight PEGs and a ternary phase diagram of polysorbate 80 with PEG 400 and water are presented. Two phases were observed in the binary mixtures when the concentration of PEG 200, PEG 300, PEG 400, or PEG 600 was >55%(w/w). The miscibility of the binary mixtures increases with an increase in temperature; the upper consolute temperatures of PEG 200–polysorbate 80, PEG 300–polysorbate 80, PEG 400–polysorbate 80, and PEG 600–polysorbate 80 mixtures were 100, 85, 75, and 40 °C, respectively. The upper consolute temperature of PEG 1000–polysorbate 80 could not be determined because the melting temperature of the mixtures is ∼40 °C and the consolute temperature appeared to be less than this temperature. The decrease in upper consolute temperature with an increase in PEG molecular weight indicated a greater miscibility of the two components. In the ternary system, phase separation of polysorbate 80 was observed when the concentration of PEG 400 was >50–60 % (w/w), possibly because of the high exclusion volume of PEG 400. © 2000 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 89:946–950, 2000