Interactions between Solid Surfaces Mediated by Polyethylene Oxide Polymers: Effect of Polymer Concentration

Langmuir ◽  
2013 ◽  
Vol 29 (35) ◽  
pp. 11038-11045 ◽  
Author(s):  
Xiaoling Wei ◽  
Xiangjun Gong ◽  
To Ngai
Keyword(s):  
Polyethylene Oxide ◽  
Polymer Concentration ◽  
Solid Surfaces

scholarly journals Electrospinning of Hyaluronan Using Polymer Coelectrospinning and Intermediate Solvent

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1517 ◽  
Author(s):  
Lenka Vítková ◽  
Lenka Musilová ◽  
Eva Achbergerová ◽  
Antonín Minařík ◽  
Petr Smolka ◽  
...  
Keyword(s):  
Polyethylene Oxide ◽  
Average Molecular Weight ◽  
Polymer Concentration ◽  
Sodium Hyaluronate ◽  
Electrospinning Process ◽  
Poly Vinyl Alcohol ◽  
Solvent Mixtures ◽  
Fluorescence Confocal Microscopy ◽  
Dc Electric Field ◽  
Solution Surface

In the current study, we present methods of sodium hyaluronate, also denoted as hyaluronan (HA), nanofiber fabrication using a direct-current (DC) electric field. HA was spun in combination with poly(vinyl alcohol) (PVA) and polyethylene oxide (PEO) and as a pure polymer. Nonaggressive solvents were used due to the possible use of the fibers in life sciences. The influences of polymer concentration, average molecular weight (Mw), viscosity, and solution surface tension were analyzed. HA and PVA were fluorescent-labeled in order to examine the electrospun structures using fluorescence confocal microscopy. In this study, two intermediate solvent mixtures that facilitate HA electrospinning were found. In the case of polymer co-electrospinning, the effect of the surfactant content on the HA/PVA electrospinning process, and the effect of HA Mw on HA/PEO nanofiber morphology, were examined, respectively.

Substrate-Dependent Features of Polyethylene Oxide (Peo) Adsorption from Aqueous Solution: Competitive Adsorption Versus Surface Relaxations

1994 ◽  
Vol 366 ◽  
Author(s):  
M. M. Santore ◽  
V. A. Rebar
Keyword(s):  
Aqueous Solution ◽  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Polyethylene Oxide ◽  
Weight Distribution ◽  
Adsorption Process ◽  
Polymer Concentration ◽  
Hydroxyethyl Cellulose ◽  
Total Internal Reflectance ◽  
The Impact

ABSTRACTThis work employed total internal reflectance fluorescence (TIRF) to examine the adsorption kinetics of polyethylene oxide (PEO) on silica from aqueous solution in controlled shearing flow. Studies with PEO, fluorescently labeled such that TIRF tracked the chain number on the surface, exhibited an overshoot in the early stages of adsorption. This overshoot was not seen with other polymers such as polyvinyl alcohol, and hydroxyethyl cellulose, possibly because these other polymers were labeled such that TIRF measured the interfacial mass. Indeed, reflectometry studies of PEO adsorption, sensitive to interfacial mass, showed no overshoot. This suggests that the overshoot results from the selectivity of the surface for high molecular weight populations within a polydisperse sample. Initially short chains adsorb because they diffuse to the surface quickly. At longer times, higher molecular weight chains reach the surface and replace the short chains. This evolution occurs as the mass coverage increases (according to reflectivity) but the number of adsorbed chains, and hence the TIRF signal decrease at long times. A study of the impact of the molecular weight distribution confirmed this hypothesis.Several complications to the molecular weight selectivity hypothesis, however, arose: First, the same PEO samples which overshot during adsorption on silica showed no overshoot on a polystyrene substrate. This suggested that the ability to overshoot was governed by the substratesegment interactions, even though the molecular weight distribution within the sample determined the overshoot shape. Further, the effect of transport conditions (wall shear rate, bulk polymer concentration) were not completely consistent with the molecular weight competition hypothesis, which was based on surface-solution equilibrium, taking into account transport-limited rates of adsorption. Finally certain runs, where the adsorption process was interrupted by solvent flow and later allowed to proceed, never reached the full coverage seen for uninterrupted runs. Hence, the surface coverage and possibly the chain configurations can depend on the history of the adsorption process, a feature which points to surface relaxations and non-equilibrium structures.

scholarly journals Self-Seeding Procedure for Obtaining Stacked Block Copolymer Lamellar Crystals in Solution

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1676
Author(s):  
Brahim Bessif ◽  
Thomas Pfohl ◽  
Günter Reiter
Keyword(s):  
Block Copolymer ◽  
Polyethylene Oxide ◽  
Homogeneous Nucleation ◽  
Diblock Copolymers ◽  
Polymer Concentration ◽  
Solubility Limit ◽  
The Self ◽  
Lateral Size ◽  
Linear Extrapolation ◽  
Lamellar Crystals

We examined the formation of self-seeded platelet-like crystals from polystyrene-block-polyethylene oxide (PS-b-PEO) diblock copolymers in toluene as a function of polymer concentration (c), crystallization temperature (TC), and self-seeding temperature (TSS). We showed that the number (N) of platelet-like crystals and their mean lateral size (L) can be controlled through a self-seeding procedure. As (homogeneous) nucleation was circumvented by the self-seeding procedure, N did not depend on TC. N increased linearly with c and decayed exponentially with TSS but was not affected significantly by the time the sample was kept at TSS. The solubility limit of PS-b-PEO in toluene (c*), which was derived from the linear extrapolation of Nc→ 0 and from the total deposited mass of the platelets per area (MCc→0), depended on TC. We have also demonstrated that at low N, stacks consisting of a (large) number (η) of uniquely oriented lamellae can be achieved. At a given TC, L was controlled by N and η as well as by ∆c=c−c∗. Thus, besides being able to predict size and number of platelet-like crystals, the self-seeding procedure also allowed control of the number of stacked lamellae in these crystals.

scholarly journals Variation of the Hydrodynamic Polymer Layer Thickness on Solid Surfaces with Molecular Weight and Concentration

1995 ◽  
Vol 12 (3) ◽  
pp. 259-265 ◽  
Author(s):  
S. Millot ◽  
J.L. Loubet ◽  
J.M. Georges
Keyword(s):  
Molecular Weight ◽  
Layer Thickness ◽  
Polymer Concentration ◽  
Surface Force ◽  
Extensive Study ◽  
Solid Surfaces ◽  
Low Molecular Weight ◽  
Molecular Weight Polymer ◽  
Molecular Weights

An extensive study on the determination of the 'hydrodynamic' layer thickness of polymer solutions and melt polymers was conducted with a surface force apparatus. For different concentrations and polymer molecular weights, a 'hydrodynamic layer' of fluid was detected on each solid surface which did not contribute to the flow. These thicknesses, denoted as LH, are compared to the characteristic polymer dimensions and the hydrodynamic (RH) and gyration (Rg) radii. It appears that in contrast to the molecular weight, polymer concentration has little effect on the relative hydrodynamic layer thickness (LH/2RH, LH/2Rg). Indeed, this ratio indicates that two coils of low molecular weight and one coil of high molecular weight are 'immobile' on the solid surfaces. The mechanism responsible could be entanglement of the free (unattached) chains in the bulk with immobilized chains on the surface.

Structures Formed by Cryoprotective Agents Used in Freezc-Etching

1971 ◽  
Vol 29 ◽  
pp. 448-449
Author(s):  
G. G. Cocks ◽  
C. E. Cluthe
Keyword(s):  
Aqueous Solution ◽  
Polyethylene Oxide ◽  
Liquid Nitrogen Temperature ◽  
Ice Crystals ◽  
Etching Technique ◽  
Structural Constituent ◽  
Cryoprotective Agents ◽  
Quick Freezing ◽  
Freeze Etching ◽  
Fractured Surface

The freeze etching technique is potentially useful for examining dilute solutions or suspensions of macromolecular materials. Quick freezing of aqueous solutions in Freon or propane at or near liquid nitrogen temperature produces relatively large ice crystals and these crystals may damage the structures to be examined. Cryoprotective agents may reduce damage to the specimem, hut their use often results in the formation of a different set of specimem artifacts.In a study of the structure of polyethylene oxide gels glycerol and sucrose were used as cryoprotective agents. The experiments reported here show some of the structures which can appear when these cryoprotective agents are used.Figure 1 shows a fractured surface of a frozen 25% aqueous solution of sucrose. The branches of dendritic ice crystals surrounded hy ice-sucrose eutectic can be seen. When this fractured surface is etched the ice in the dendrites sublimes giving the type of structure shown in Figure 2. The ice-sucrose eutectic etches much more slowly. It is the smooth continuous structural constituent surrounding the branches of the dendrites.

Computer averaging of lattice images of poly-4-methyl-pentene-1 (P4mp1): Noise created artifacts

1987 ◽  
Vol 45 ◽  
pp. 388-389
Author(s):  
P. Pradère ◽  
J.F. Revol ◽  
R. St. John Manley
Keyword(s):  
Low Dose ◽  
Polymer Concentration ◽  
Processing System ◽  
Limiting Factor ◽  
Dilute Solution ◽  
New Techniques ◽  
Dose Unit ◽  
Lattice Images ◽  
Dose Imaging ◽  
Imaging Conditions

Although radiation damage is the limiting factor in HREM of polymers, new techniques based on low dose imaging at low magnification have permitted lattice images to be obtained from very radiation sensitive polymers such as polyethylene (PE). This paper describes the computer averaging of P4MP1 lattice images. P4MP1 is even more sensitive than PE (total end point dose of 27 C m-2 as compared to 100 C m-2 for PE at 120 kV). It does, however, have the advantage of forming flat crystals from dilute solution and no change in d-spacings is observed during irradiation.Crystals of P4MP1 were grown at 60°C in xylene (polymer concentration 0.05%). Electron microscopy was performed with a Philips EM 400 T microscope equipped with a Low Dose Unit and operated at 120 kV. Imaging conditions were the same as already described elsewhere. Enlarged micrographs were digitized and processed with the Spider image processing system.

Sign in / Sign up

Export Citation Format

Share Document