Dependence of depletion layer thickness on polymer concentration determined by Vincent's pragmatic and Donath's electrophoretic theories

Zhivkov, Alexandar M.

doi:10.1016/j.jcis.2007.03.064

Cited by 8 publications

(7 citation statements)

References 17 publications

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“…The high surface area of the swollen MMT provides an ideal two‐dimensional plate for polymer interaction and assumed similarity to plate and sphere interaction. For POP and Cu(II) coordinating with anionic silicates, the silicate d‐ spacing was equal to the diameter of the polyether random coil3: …”

Section: Resultsmentioning

confidence: 99%

“…Each polymer molecule was adsorbed onto both clay surfaces and, thereby, induced a reduction of the interlayer spacing by a phenomenon known as polymer bridging flocculation. 3–6 The interaction between the clay layers and the polymer changed its crystalline morphology. The crystal formation suggested that the induced clay surface kinetically favored the formation of a nematic phase.…”

Section: Resultsmentioning

confidence: 99%

“…Both organo–amine and inorganic metal salts can be used to swell clays through ion exchange for pillared silicates 1, 2. In previous studies, poly(oxypropylene)amine (POP) has had a strong effect on the expansion of the basal spacing ( d ‐spacing) and has formed well‐dispersed hybrid organoclays 3–6. The steric random coils of the polymers are assumed to be a major effect of the expansion of the d ‐spacing of the organoclays.…”

Section: Introductionmentioning

confidence: 99%

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Self‐assembled and crystallized composites made from poly(ether amine) and montmorillonite in the presence of copper(II) ions

Lee

Tsai

Cheng

et al. 2010

J of Applied Polymer Sci

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Self-assembled and crystallized composites made from montmorillonite (MMT) by intercalation with poly(ether amine) salts and copper(II) [Cu(II)] ions simultaneously were studied. The manipulation of the silicate unit structure of the secondary (001) lattice by physically imposed osmotic pressure on the platelet interlayer was used. Divalent copper salt assisted a strong depletion effect with balancing the counterions in the clay interlayer and resulted in the extension of the dimensions of the (001) plane by increasing the spacing expansion by more than two orders of magnitude. The simultaneous adsorption of Cu(II) and intercalation of poly(oxypropylene)-amine (POP) salts onto the MMT units ultimately minimized their amorphous aggregation through electrostatic attraction between the negative surface and positive edge among the silicate units. Alternatively, the attraction force through face-to-face stacking on the silicate surface is proposed, and the conformation of the POP/Cu(II) complex aligned with the approaching platelets to form orderly structures. X-ray diffraction of the MMT units exhibited a high order of reflection (i.e., (006)) in Bragg's pattern; this implied a repetitive regularity between the plate-plate distances. The high regularity disappeared when the Cu(II) adsorption exceeded the critical clay cation-exchange capacity of 1.4. The conformation of the flexible polyether backbone was altered and could no longer sustain the plate distance and the symmetric packing was destroyed when the basal spacing was decreased from 82.6 to 18.0 Å .

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Self‐assembled and crystallized composites made from poly(ether amine) and montmorillonite in the presence of copper(II) ions

Lee

Tsai

Cheng

et al. 2010

J of Applied Polymer Sci

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“…A very low positive Z-potential value was measured for liposomes containing DDAB, probably due to the masking effect produced by surface polyoxyethylene chains on the positive charge of DDAB. In the mean time, PEG can reduce the liposome electrophoretic mobility as a result of an hydrodynamic effect (Woodle et al, 1992;Zhivkov 2007) The presence of D-CS further enhanced the positive charge of the system, therefore giving a positive Z-potential value (Figure 1). Due to the high hydrophilic properties of this drug, it is conceivable that it was principally distributed within the aqueous compartments; thus the higher EE% observed for charged MLV with respect to the neutral liposomes was due to the higher amount of aqueous medium present in these vesicles.…”

Section: Resultsmentioning

confidence: 99%

Development of a Liposome Formulation for D-Cycloserine Local Delivery

Musumeci

Ventura

Giannone

et al. 2008

Journal of Liposome Research

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Multilamellar liposomes loaded with D-cycloserine (D-CS) were prepared by a thin layer evaporation technique, followed by freezing and thawing cycles. Charged components and bioadhesive material, such as distearolylphosphatitylethanolamine covalently coupled with methoxypolyethyleneglycol, were used to prepare liposomes with different physico-chemical and technological properties. Negatively charged liposomes showed higher D-CS encapsulation efficiency (about 37%, w/w) than neutral and positively charged liposomes (about 5 and 17%, w/w, respectively). All formulations showed in vitro, after a burst effect, a prolonged release of the encapsulated drug.Lipid vesicles made of dipalmitoylphosphatidylcholine (DPPC) were used as a biomembrane model to evaluate in vitro the interaction of D-CS with biological membranes. Differential scanning calorimetry was used as a simple and noninvasive technique of analysis. D-CS was distributed in the aqueous compartments of liposomes for interaction with the phospholipid polar head-groups (enhancement of ΔH value). However, due to its high diffusibility the drug was also able to freely permeate through DPPC liposomes, altering during this passage the hydrophobic domains of the bilayers.Stability studies were performed at different temperatures and pH values to assay the integrity of the drug during the liposome production steps. D-CS was rapidly degraded at acidic pH, but no significant hydrolysis was observed at pH 7.4 after 7 days.

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“…So the effect of bulk viscosity on the mobility is reduced. By changing the ionic strength of samples, Debye length changes and provides the possibility to estimate the depletion layer thickness [114,129]. As long as the depletion layer is considerably larger than Debye length, the actual mobility will be higher than the predicted mobility value based on bulk viscosity.…”

Section: Introductionmentioning

confidence: 99%

Impact of cellular and medium properties on depletion-mediated red cell aggregation

Rad¹

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Dependence of depletion layer thickness on polymer concentration determined by Vincent's pragmatic and Donath's electrophoretic theories

Cited by 8 publications

References 17 publications

Self‐assembled and crystallized composites made from poly(ether amine) and montmorillonite in the presence of copper(II) ions

Self‐assembled and crystallized composites made from poly(ether amine) and montmorillonite in the presence of copper(II) ions

Development of a Liposome Formulation for D-Cycloserine Local Delivery

Impact of cellular and medium properties on depletion-mediated red cell aggregation

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