Polyethylene Glycol Macromolecules Research Articles

From micelle-like aggregates to extremely-stretchable, fatigue-resistant, highly-resilient and self-healable hydrogels

The applications of hydrogels can be greatly expanded by the improvement of extensibility and toughness. Despite remarkable efforts in tough hydrogels, little is known about the fracture strain above 100 mm/mm due to the inhomogeneous chemical networks and inefficient energy-dissipative mechanism. Herein, micelle-like aggregates were obtained from the self-assembly of dually alkyl-modified polyethylene glycol (PEG) in water, serving as dynamic junctions to fabricate hydrogel via the aqueous radical polymerization of acrylamide (AM) monomers in water with the assistance of methylene bisacrylamide. Unlike hairy micelles, interactions of aggregates and hydrogel framworks were improved obviously through pronounced entanglements between PEG and PAM macromolecules. Meanwhile, the reversible break/reformation of micelle-like aggregates upon stretching empowered the gel an efficient energy-dissipative mechanism. Therefore, hydrogels with extreme stretchability (tensile strain = 150 mm/mm) and high toughness (toughness = 24.8 MJ/m3) were generated. Remarkably, their mechanics could be easily modulated by varying alkyl terminals and molecular weights of PEG to control the strength of hydrophobic domains and physical entanglements, respectively. Two examples were displayed: ultra-sensitive gels for wearable sensors and mechano-responsive molecule release. Impressively, the gauge factor was 60.29 under large deformation (strain > 20 mm/mm), outperforming most conductive hydrogels. As the first research to tune the macroscopic property of the hydrogel by delicately adjusting the microstructures of micelles, and interactions between micelles and gel network, this work not only expands the applications of soft materials but also sheds light on fabricating super-stretchable matters, making it promising candidates for flexible sensors, artificial skins, and drug delivery systems.

Determining Conformations and Sizes of Polyethylene Glycol Macromolecules in Water–Polyethylene Glycol–LiOH Systems by the Viscometry Method

The kinematical viscosity of water-polyethylene glycol-LiOH systems is studied at 293.15 K for the LiOH molar fraction of 0–0.05 and the PEG concentration of 0–5 g/length. Polyethylene glycol fractions of different molecular masses (1000, 1500, 3000, 4000, and 6000) are considered. Experimental data on the kinematic viscosity for a given LiOH concentration are used to calculate the following quantities: intrinsic viscosity of studied solutions, Huggins coefficient, parameter α in the Mark-Houwink equation, swelling coefficient of polyethylene glycol macromolecules, intrinsic viscosity in the θ solvent, mean square distance of the PEG macromolecular chain in the solution and in the θ solvent, length of the Kuhn segment in the solution and the θ solvent. It is shown that macromolecular polyethylene glycol coils are permeable for the surrounding liquid (water-LiOH) and that their volumes decrease and the macromolecule flexibility increases with increasing LiOH concentration.

Viscometric Determination of the Conformations and Sizes of Polyethylene Glycol Macromolecules in Aqueous Solutions

The kinematic viscosities of solutions of polyethylene glycol (PEG) of different molecular weights (1000, 1500, 3000, 4000, and 6000) are studied at 293.15–323.15 K in the 0–5 g/dL range of concentrations. Parameters are calculated according to the obtained data: characteristic viscosity, the Huggins constant, parameter α in the Kuhn–Mark–Houwink equation, characteristic viscosity in a θ solvent, the coefficient of swelling of the macromolecular coil in solution, root-mean-square distance of PEG macromolecular chain, and the length of Kuhn segments. It is found that the macromolecular coil is partially permeable for the surrounding liquid (water) and opens slightly. It was shown that the PEG molecules shrink as the temperature is raised, as is typical of flexible chain polymers.

Jetting Performance of Polyethylene Glycol and Reactive Dye Solutions.

The jetting performance of dye inks determines the image quality, production efficiency, and lifetime of the print head. In the present study, we explored the jetting performance of mixed solutions of polyethylene glycol (PEG) and reactive dye by testing the visible absorption spectra, rheological properties, and surface tension, in addition to the observation of droplet formation. The results indicate that PEG macromolecules could change the aggregate groups of Red 218 molecules into smaller ones through hydrophobic interactions and separation effect. The addition of PEG into the dye solution increased the viscosity and decreased the surface tension. In the whole shear rate range tested, the 10% and 20% PEG400, as well as the 30% PEG200 dye solutions, showed good Newtonian fluid behavior. PEG macromolecules improved the droplet formation of the dye solutions. Increasing the PEG400 concentration to 30% and 40% resulted in elimination of the formation of satellites and the formation of ideal droplets at 10,000 Hz jetting frequency. A 30% PEG600-dye solution with the Z value of 4.6 formed the best spherical droplets at 10,000 Hz and produced perfect color images on cotton fabrics.

Effect of sodium hydroxide on the interactions of polyethylene glycol macromolecules with water molecules

The rheological properties of dilute water solutions of polyethylene glycols with different molecular mass (1000, 3000, 6000, 8000, 20,000) were investigated in the temperature range 293-323°K in the presence of sodium hydroxide (0.1 mol/l). The intrinsic viscosities, Huggins constants, mean-square distance between the ends of the macromolecular chain, crossover concentrations and activation energies of viscous flow have been determined vs. temperature and molecular mass of polymers. It has been established that the macromolecular coils in the presence of sodium hydroxide (0.1 mol/l) in aqueous solutions of polyethylene glycols accept the unperturbed state as in theta solutions and the intrinsic viscosity becomes very sensitive to the molecular mass of polymers. The new approach for estimating the interaction energy per volume fraction between the macromolecule and solvent molecule has been proposed.

A polymeric prodrug of 5-fluorouracil-1-acetic acid using a multi-hydroxyl polyethylene glycol derivative as the drug carrier.

PurposeMacromolecular prodrugs obtained by covalently conjugating small molecular drugs with polymeric carriers were proven to accomplish controlled and sustained release of the therapeutic agents in vitro and in vivo. Polyethylene glycol (PEG) has been extensively used due to its low toxicity, low immunogenicity and high biocompatibility. However, for linear PEG macromolecules, the number of available hydroxyl groups for drug coupling does not change with the length of polymeric chain, which limits the application of PEG for drug conjugation purposes. To increase the drug loading and prolong the retention time of 5-fluorouracil (5-Fu), a macromolecular prodrug of 5-Fu, 5-fluorouracil-1 acid-PAE derivative (5-FA-PAE) was synthesized and tested for the antitumor activity in vivo.MethodsPEG with a molecular weight of 38 kDa was selected to synthesize the multi-hydroxyl polyethylene glycol derivative (PAE) through an addition reaction. 5-fluorouracil-1 acetic acid (5-FA), a 5-Fu derivative was coupled with PEG derivatives via ester bond to form a macromolecular prodrug, 5-FA-PAE. The in vitro drug release, pharmacokinetics, in vivo distribution and antitumor effect of the prodrug were investigated, respectively.ResultsThe PEG-based prodrug obtained in this study possessed an exceedingly high 5-FA loading efficiency of 10.58%, much higher than the maximum drug loading efficiency of unmodified PEG with the same molecular weight, which was 0.98% theoretically. Furthermore, 5-FA-PAE exhibited suitable sustained release in tumors.ConclusionThis study provides a new approach for the development of the delivery to tumors of anticancer agents with PEG derivatives.

Flexible chains of ferromagnetic nanoparticles.

We report the fabrication of flexible chains of ferromagnetic Ni nanoparticles that possess the ability to adapt other than the typically observed rigid (nearly) straight configurations in the absence of an external magnetic field. The dynamic mobility of the ferromagnetic chains originates from a layer of densely grafted polyethylene glycol macromolecules enveloping each nanoparticle in the chain. While ferromagnetic chains of unmodified Ni nanoparticles behave as stiff nickel nanorods, the chains made of the grafted nanoparticles demonstrate extreme flexibility. Upon changing the direction of the field, and inevitably going through a zero-field point, the shorter chains undergo chain-globule-chain transformation. The longer chains can bend to a high degree, attaining "snake-like" configurations.

Conformational characteristics of polyethylene glycol macromolecules in aqueous solutions according to refractometry data

The aqueous solutions of polyethylene glycols with molecular masses of 600, 1000, 1500, 3000, 6000, and 20000 were studied by refractometry. The conformational polarizabilities, mean-square distances between the ends of the macromolecular chain, segment lengths, and the number of Kuhn segments in a macromolecule were determined using the Lorentz-Lorentz equation. The polarizability of a hydrated macro-molecule was represented as the sum of polarizabilities of the nonhydrated macromolecule with retained conformation and polarizabilities of the water molecules involved in hydration of macromolecules. The size of macromolecules stabilized starting from a certain concentration. It was concluded that the initial concentration of stabilization shifts toward low concentrations as the molecular mass of polyethylene glycol increases. The dependence of the mean-square distance between the ends of the macromolecular chain on the number of Kuhn segments was expressed as the exponential function with index 0.3.

A Modified Osmotic Direct Shear Apparatus for Testing Unsaturated Soils

Most hydro-mechanical models for unsaturated soil models require shear strength characteristics of the soil in order to determine the pertinent model parameters. Moreover, one needs to know the shear strength of unsaturated soils when dealing with stability problems in engineering practices. Because matric suction affects the shear strength of unsaturated soils, a suitable apparatus must be capable of imposing and/or measuring suction during tests. Shear tests on unsaturated soils are usually performed using the axis translation technique. This method covers a low range of matric suctions that corresponds to relatively high degrees of saturation for fine grained soils. Thus, it is essential to develop new techniques to extend the range of suctions for these soils. In this study, a modified direct shear device is introduced that uses the osmotic method to impose the desired matric suction. A polyethylene glycol (PEG) solution is circulated all around the bottom of the soil sample to impose the suction, and a semi-permeable membrane is introduced between the soil and the PEG solution that permits water swap but prevents the PEG macromolecules from crossing the membrane. Using this technique, the suction is controlled and kept constant during the test. The special shear box design described in this paper minimizes the potential for membrane rupture during the test. Shear stress, as well as the vertical and horizontal displacement, is recorded using an auto-logging device. The suitability of the apparatus to perform direct shear tests at relatively high suction values is investigated via tests carried out on Shiraz silty clay. In these tests, soil specimens are subjected to suctions of up to 800 kPa during shearing. The results indicate that the shear strength and shear induced dilation of the soil samples increase with suction.

Synthesis and properties of porous silica obtained by the template method

Micromesoporous samples of SiO2 were synthesized by the sol-gel method using tetraethoxysilane as a starting reagent and 1–5 wt % cetylpyridinium chloride as a template under the conditions of preadsorption of colloid silica by polyethyleneglycol macromolecules. The adsorption and texture of the samples were studied by the low-temperature nitrogen adsorption-desorption technique. Preadsorption of silica sol was shown to affect the adsorption and capillary-condensation properties of silica. The surface area and the volume of mesopores increased at cetylpyridinium concentrations higher than 1 wt %. The micropore volume increased to a maximum. The capillary-condensation hysteresis loop of H4 type transformed into an H3 loop according to the IUPAC classification.

Investigation of PEG adsorption on the surface of zinc oxide nanoparticles

The influence of polyethylene glycol (PEG) on the adsorption at zinc oxide/polymer solution interface has been determined. PEG macromolecules bond with the solid surface mainly via the –OH group of the surface of ZnO nanoparticles, which may interact with PEG through hydrogen bonding. Adsorption isotherms demonstrate the marked influence of the PEG molecular weight and the concentration of polymer solution on the extent of adsorption. The thickness of the adsorbed polymer layer on ZnO nanoparticles was calculated on the basis of measurements of their suspension viscosities in the absence and presence of adsorbed polymer. Results show that the thickness of the adsorption layer increased with increasing polymer molecular weight and the concentration of polymer solution. The main factors responsible for the changes in zeta potential were determined on the basis of the data obtained. The shift of the slippage plane away from the surface of ZnO nanoparticles plays major role below pH iep. Above pH iep, the blockage of the adsorption sites is the predominant factor.

Investigation of the Structure of Polyethylene Glycol (PEG) Layers Adsorbed at the Alumina-Polymer Solution Interface

The investigations presented were aimed at a description of the structure of the adsorbed layers of polyethylene glycol (PEG) on the surface of Al2O3. This was obtained from measurements of the adsorption heat of PEG macromolecules as well as of 1,2-dimethoxyethane (C4 H10O2) and tetraethylene glycol dimethyl ether (C10H22O5), i.e. low-molecular weight compounds constituting the monomers forming the PEG chain.The results allowed the fraction of polymer segments bonding directly to the Al2O3 surface to be estimated. Other information obtained from calculations based on the Scheutjens–Fleer theory included the distribution of chain segment conformations as trains, loops and tails, together with a determination of some structural changes and the sizes of PEG macromolecules as they moved from the bulk solution to the solid phase surface. The thickness of the adsorbed macro-molecular polymer layers on the alumina surface was also determined. All these data enabled an approximate description to be made of the p...

Reversed-phase high-performance liquid chromatography of polyethers: Comparison with a theory for flexible-chain macromolecules

Reversed-phase adsorption chromatography retention modes of polyethylene glycol (PEG), its mono and dimethyl ethers (MME and DME) and polypropylene glycol (PPG) are studied both experimentally and theoretically. The experimental conditions were: narrow- and wide-pore Spherisorb C 18 adsorbents and two mixed-solvent systems (methanol–water and acetone–water) as mobile phases. At varying compositions of the mobile phase, fully-resolved chromatograms of polyether samples were obtained, in which all peaks could be identified, and the dependencies of the distribution coefficient on the degree of polymerization for PEG and PPG molecules were extracted by processing these chromatograms. The data were interpreted by using a theory of homopolymers based on a continuum Gaussian chain model of flexible macromolecules and a slit-like model of pores of the stationary phase. Two regimes of an adsorption chromatography of macromolecules are examined in relation to the well-known Martin rule, the role of pore size and the end-group effects being discussed. The theory proved to describe the experimental data on both polymers well, in the whole range of molecular masses studied, and thermodynamic parameters characterizing interactions of ethylene oxide and propylene oxide (PO) repeating units in polyether molecules with the adsorbent pore walls have been determined from a comparison of the theory with the experimental data. The conditions corresponding to the critical chromatography mode are estimated from the thermodynamic data for PEG and methanol–water system as being at about 76% of methanol, while for the PPG and acetone–water system, it is shown that such critical conditions at the given temperature are not attainable. Additionally, the mean thickness H of adsorbed PEG and PPG macromolecules was estimated as being equal to about 3–10 Å. The parameter H proved to be a decreasing function of the water content in the mixed solvent. The same estimate of thickness H≈2.6 Å is obtained for both polymers in pure water.

Adsorption-exclusion behaviour of polyethylene glycol macromolecules during chromatography

The authors have investigated the chromatography of polyethylene glycols on crosslinked copolymer Solose K sorbents with varied hydrophobic-hydrophilic properties. The experimental data as a whole are described by the theoretical dependences of the distribution coefficient on M. It is proposed that the chromatographic regime be characterized by the parameter of adsorption interaction τ, a measure of the deviation of the system from critical conditions. The critical conditions are found delineating the regimes of exlusion and adsorption chromatography. It is shown that the transition from exlusion to adsorption comes about with increase in the content in the sorbent of the hydrophobic components and for sorbents with fixed composition with fall in pH or with rise in temperature. It is concluded that the hydrophobic effects play a determinant role on adsorption in the polyethylene glycol-Solose K systen,.

Selective properties of hollow fibres for ultrafiltration

The selective properties of hollow fibres used in the separation of solutions of poly-ethylene glycols and proteins have been investigated. It has been shown that the increase in retention coefficient and specific permeability as the velocity of the stream increases, in the separation of solutions of kinetically relatively flexible polyethylene glycol molecules, is not connected with the phenomenon of concentration polarization. but can be explained by the deformability of the tangles of polyethylene glycol macromolecules on flow of the solution in thin capillaries (hollow fibres). Optimum ultrafiltration conditions have been determined. Complete retention curves have been constructed for the hollow fibre, which make it possible to determine its region of use.